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Updated: 55 min 14 sec ago

Show your affection with physics valentines

Tue, 02/13/2018 - 16:35

When it comes to love, sometimes you have to say it with science.


Valentine’s Day is upon us. If you’re still trying to find the right words to tell the loved ones in your life how you feel, look no further. The staff of symmetry has assembled another round of valentines so you can let the universal language of physics do the talking. (And if you need more options, you can check out our previous valentines here.)

Love is a mysterious force, and so is dark energy. Tell your valentine how they broaden your horizons:

Artwork by Sandbox Studio, Chicago with Ana Kova

Show the depths of your unity with this card. Einstein would approve!

Artwork by Sandbox Studio, Chicago with Ana Kova

Like someone with a magnetic personality? Accelerate your way into their heart with this valentine:

Artwork by Sandbox Studio, Chicago with Ana Kova

Some particles like neutrinos can be found solo, but not quarks. If a strong force binds you together, let your beloved know:


Artwork by Sandbox Studio, Chicago with Ana Kova

Of course, the universe is made of matter and antimatter, so you might find yourself in need of an anti-valentine. If that’s the case, let others know about your charged feelings with this message:

Artwork by Sandbox Studio, Chicago with Ana Kova

Subatomic Smackdown

Fri, 02/09/2018 - 20:09

When it comes to talent, versatility and the power to change the world, which atomic particle is the champ? Read what our four contenders have to say—then you decide.

Physics fans, are you ready to rumble?

Of course you are — and you’ve come to the right place. In the text that follows, you will have a ringside seat to perhaps the most anticipated skirmish in science history, as four atomic adversaries duke it out for the coveted title of Most Awesome Subatomic Particle of the Millennium.

More rousing than the Rumble in the Jungle, more chilling than the Thrilla in Manila, we present to you, ladies and gentlemen, the (drumroll, please) Subatomic Smackdown.

There will be no messy blood, sweat or other bodily fluids involved in this brainy battle. This is a war of words, ideas and wit based in science, from which one, and only one, of these four deserving combatants will emerge as victor. Introducing:

In the blue corner, championed by CERN (the European Organization for Nuclear Research) near Geneva, Switzerland, and weighing in at 938.27231 megaelectronvolts (MeV), is the proton.

In the red corner, supported by SLAC National Accelerator Laboratory in Menlo Park, California, USA, and weighing in at—well, nothing, really—is the photon.

In the purple corner, championed by the National High Magnetic Field Laboratory in Tallahassee, Florida, USA, and weighing in at 0.51099906 MeV, is the electron.

Finally, in the green corner, rooted on by the Institute for Quantum Matter at Johns Hopkins University in Baltimore, Maryland, USA, and weighing in at 939.56563 MeV, is the neutron.

This epic physics feud will take place over four rounds, as each challenger (with a little help from their supporters) will argue why it, and it alone, deserves to hold the title of Most Awesome Subatomic Particle.

So … electronvolt for electronvolt, which particle packs the most impressive punch? Read on, award points as you go, then weigh in on who you believe emerges as champion of this quantum quarrel.

  Round 1: The Proton

Pay heed to this smashing subatomic celebrity, used in medicine and to produce neutrinos, antiprotons and, of course, the God particle.

Step aside, lightweights. The proton has arrived. And I’m positive that I’m the very best.

You may have heard of me. Ever seen a model of an atom? Right there in the middle of everything: protons.

Fighter Stats
  • Weight: 938.27231 MeV
  • Symbol: p+
  • Year discovered: 1911
  • Charge: positive

Yes, there are also neutrons in the nucleus. But they’re lucky just to be there, aren’t they? Look up any element's atomic number and you'll see which particles really count for something. Protons are the best, and scientists know it. After all, my name comes from the Greek word for “first.” Electrons? They’re fighting just to be in our orbit.

What else? Those hadronsin the Large Hadron Collider (LHC) at CERN? Protons, of course.

I don’t like to brag, but do you know about the Higgs boson? The “God particle”? The last undiscovered piece in the Standard Model of particle physics, the one scientists spent five decades trying to find? Do you know who finally discovered that particle?

Protons did. When LHC scientists crashed us together, we made so many of those bosons that scientists couldn’t help but see them. There’s a reason they built a 17-mile accelerator — spanning two countries! — just for us.

The takeaway here? Protons make an impact.

So maybe I don’t zip around the LHC at exactly the speed of light. I do get pretty close, and besides who would want to? I am a particle of substance. I have mass.

Unlike you photons and electrons, I’m not just some simple, point-like particle. I have an inner self, full of quarks and gluons. The force that holds them all together? The strong nuclear force — which, by the way, is almost 140 times as strong as the electromagnetic force (sorry not sorry, electrons).

Unlike some of you, I can stand up for myself. Push me and I’ll push back, converting energy into brand new gluons and virtual particles. I’m not some clumsy electron, speeding around just as fast as you please.

What I am is creative — not to mention multitalented. Higgs bosons aren’t the only particles I can make. Need some neutrons? Some neutrinos? How about anti-protons or rare isotopes? Protons can make any of those: Just point us toward the right target.

You might think I’d get tired of being so amazing. You might think that, like some neutron, I’d eventually wear out, give up and come apart. But I am rock solid. As far as scientists know, I will never decay. And if I do, I’ll still probably last longer than every planet, star and galaxy around.

In sum, protons are collections of quarks and gluons, held together by the strong force, possibly for eternity. You can find them in everything built of atoms, and they’re key players in both medicine and basic research. In sum, protons are the best.


Written with the assistance of Kathryn Jepsen

Round 2: The Photon

Lighter than a butterfly, faster than a bee (by far) — no other particle can compete with me!

Fighter Stats
  • Weight: massless
  • Symbol: ϒ
  • Year discovered: 1923
  • Charge: none

I go 186,000 miles
a second,1 faster than you can go,
I reckon.
I’m massless,2 in fact:
your weight holds you back.

Got my attosecond attitude,3
while gravity’s got you subdued.
I’m everywhere, nowhere;4
there’s no place
you can go where
I can’t be —
I’m the original
of particle-wave duality.5
I am all colors,
shedding light.
You can’t hide from me.

From big to ultrasmall,
don’t you know I reveal it all?
I’ll show you what the deal is:
photosynthesis6 and double helix.

With X-rays you can see inside,
deflect off atoms while I glide.
I’m coherent;7
I’m transparent;
admit it,
I’m the heir apparent.

Fast-moving fire atom,8
transmitting your datum,9
telecommunication, wifi,
bouncing through the
night sky,
13 billion miles10
from Voyager’s eye,
I fly.

See me in the sci-fi —
I destroyed Alderaan11
then in the real world
I grew the grass on your12

I come from the sun at
half a hellawatt;13
forget about it, your words
mean naught.
Your matter is trash,
time to scatter fast.

Which particle is best?
No contest.


Written with the assistance of Karl Gumerlock, Amanda Solliday and Alan Fry

  1. The speed of light is 299,792,458 meters (about 186,000 miles) per second. Nothing moves faster.
  2. Theory and experiments agree that photons have energy and momentum, but no mass.
  3. The fastest controlled laser pulses occur in just attoseconds, or billionths of a billionth of a second.
  4. Cosmic microwave background radiation, a form of light from the Big Bang, permeates our universe.
  5. Light seems to behave like a wave sometimes and a particle other times.
  6. X-ray imaging experiments have provided important clues to how life works, from DNA to photosynthesis.
  7. Light is coherent when its waves travel in fixed relationships. This is a property of lasers.
  8. In ancient Hindu physics, light rays were made of fire atoms called tejas.
  9. Examples of telecommunication that rely on photons: radiofrequency wireless signals, microwaves and fiber optics.
  10. NASA uses light to communicate with space missions billion of miles away through huge radio antennas on Earth and in space.
  11. In Star Wars, a laser from the Death Star destroys the peaceful planet.
  12. Photons drive photosynthesis and the atmospheric warming that influences Earth’s weather and climate.
  13. The solar energy output is about 0.4 x 1027 watts, an order of magnitude referred to unofficially as “hella.”
Round 3: The Electron

It might look like wizardry, but racking up a shelf of Nobel Prizes is all skill, ingenuity and inherent greatness.

It goes without saying that the electron is the greatest subatomic particle, but I’ll take the time to explain why to those confused individuals who would suggest otherwise. Although our greatness is 100 percent established by science, we do see how some might become so awestruck as to suspect that hocus-pocus is somehow involved.

Fighter Stats
  • Weight: 0.51099906 MeV
  • Symbol: e-, β-
  • Year discovered: 1897
  • Charge: negative

First out of our bag of tricks: If you are reading this on a computer or cell phone screen, you are welcome. If you want to forward this to a friend or loved one — and I hope you do — feel free to use email. And what do you think the “e” stands for, anyway? Without me, you’d be swiping on a touchscreen or banging on a keyboard to do what? Generate neutrons, protons or photons? I don’t think so.

Oh sure, the internet uses photons to transmit information, but it gets the information from electrons and it converts the information back to electrons before it arrives at its destination.

And if you are sitting down, you are also welcome. Because without the electronic bond, you’d fall right through your chair to the floor … and then through the floor … and so on. All the way down — now there’s a disappearing act!

In fact, I’m so important to everyday life that I was the first elementary particle to be discovered by scientists, a feat performed by J.J. Thomson in 1897 for which he received the Nobel Prize. In 1911, we electrons paired up at low temperatures to perform our superconductivity dance for Heike Kamerlingh Onnes. We zipped so fast through that mercury: Now you see us, now you don’t! Another Nobel Prize. It took scientists 46 years to explain that dance, thanks to our deep understanding and clever use of quantum mechanics.

Then in 1986, in a very thin layer of copper and oxygen atoms, we performed our superconductivity dance at temperatures far exceeding anything previously known. We bagged more Nobel Prizes for that discovery (Hmmmm … that name seems to keep popping up like a rabbit out of a hat!). And even though engineers are already using high-temperature superconductivity in new magnets and other technologies, physicists still haven't discovered how we do it!

That’s the thing. We electrons are genius magicians, always coming up with new tricks to amaze. But we’re also genius entrepreneurs … always providing new technologies to benefit humanity. Your other subatomic particles neither amaze nor innovate, playing the vaudeville circuit while our name is in lights on Broadway.

These days, my greatest tricks occur when I get together with quadrillions of my fellow electrons and — presto chango! — invent new collective behaviors, or electronic correlations, as scientists call them. Think of birds flocking, fish swimming in schools or other beautiful and powerful group behaviors that you’d never see or appreciate if you only studied animals as individuals. Those abilities, combined with the fact that we electrons are completely indistinguishable from each other, means that we do amazing things that still baffle scientists.

In one recent acclaimed performance, we were traveling in a material so thin we were constrained to two dimensions. Then, when scientists put us in a high magnetic field, we electrons danced around in circles and got together with the magnetic flux quanta to create new particles that — abracadabra — had only one-third of the electric charge of an electron! To put that in terms you in the classical world might understand, that’s like using a giant pile of bricks to build a wee house the size of a third of a brick.

This fractional quantum Hall effect is one of our favorite tricks. It netted us electrons more Nobel prizes and rewrote the physics textbooks to focus on topology, which should sound familiar because it landed a Nobel in 2016 — are you sensing a trend here?

Alone as individuals, together in superconducting pairs or working in countless correlated confabulations, we electrons are the best magicians and the brightest inventors of all the subatomic particles. And that is no illusion. Electron out. Mic drop.


Written with the assistance of Greg Boebinger

Round 4: The Neutron

We’re neutral, not unbiased: Revealing science secrets as we scatter, neutrons are worth our weight in the gold we create.

There really can be no disputing the superior, indeed noble stature of the neutron. I make the ultimate sacrifice in the name of science (more on that in a bit) and am the undisputed heavyweight of the subatomic world. Massless, a photon clearly lacks gravitas, while the electron, I am sorry to say, is a complete lightweight. And despite the proton’s boasts of heft, I have outweighed it for 13.8 billion years.

Fighter Stats
  • Weight: 939.56563 MeV
  • Symbol: n0
  • Year discovered: 1932
  • Charge: none

You should thank your lucky neutron stars, dear reader, for our excess mass. If neutrons were lighter than protons, then we would be the stable particles, and protons could decay into us! Hydrogen would be unstable and unable to fuel the stars, which created the carbon within you. So if we didn’t outweigh protons, you would not even be here!

I overcame a rough start. Because neutrons can only survive about 15 minutes alone (after that, regrettably, we turn into an electron, a proton and a neutrino through radioactive beta decay), just one in seven of us survived the Big Bang, by sticking to protons and forming helium-4. Indeed, without neutrons, everything would be hydrogen, the only atom that can live without us.

We neutrons coexist even at the astronomical scale. Neutron stars are made up almost exclusively of us. Why should you care? Look no farther than your golden ring: We made it, and all heavy elements, in violent neutron star collisions.

Free of electric charge, we eluded scientists longer than photons, electrons and protons. The neutrons produced by bombarding beryllium with helium-4 were initially mistaken for photons. So sad! Refined experiments by James Chadwick in 1932, however, led him to recognize that he had discovered either the neutron or the violation of energy and momentum conservation. Needless to say, it was I!

Since then, our brilliance has grown by leaps and bounds. Thanks to fancy inventions like high flux fission reactors and the spallation neutron source at Oak Ridge National Laboratory, scientists can free us from our nuclear dwellings to form neutron beams, which help them see atoms dance and electrons spin. True: X-rays are handy for figuring out the atomic structure of materials. But neutrons find things that escape even them, including tiny hydrogen atoms, even those hiding among heavy atoms! Our penetrating power gives scientists “neutron vision” to see water in an operating fuel cell, oil in an operating engine, and problems in your smartphone battery that does not hold its charge.

When a beam of us hits our target, we scatter like bouncy balls to reveal in amazing detail the good vibrations (phonons) inside. And because we spin, we feel magnetism. So when a scientist puts a material inside a powerful magnetic field and aims a beam of us at it, we divulge its magnetic secrets. We can even create and annihilate those crazy emergent particles that electrons are always waxing poetic about.

So, there you have it: We are the secret nuclear ingredient to overcoming repulsive protons; we alone form heavenly bodies that create gold mines; and when we are liberated through fission or spallation, we offer scientists an unsurpassed view of mischievous electrons and of atoms large and small. But the view comes at a price: As we are detected, we suffer the indignity of turning into lowly protons and electrons! Consider the nobility of this final act as you lock in your vote for me, objectively the best subatomic particle (n0 contest).


Written with the assistance of Collin Broholm

So … who wins the Subatomic Smackdown?

We’re moving the final round out of the ring and into the social sphere. Which particles will go down for the count and which one will take the prize? You decide.

On March 30, follow the blow-by-blow on Twitter at #SubatomicSmackdown and join a corner to support your favorite particle. But remember: We want a good clean fight, so let’s keep those tweets above the belt, everyone.

Tally your points and submit your scorecard on Smackdown Day via a Twitter poll hosted by @NationalMagLab. The champion will be selected by majority decision.

Check out our printable poster for the Subatomic Smackdown.

Artwork by Sandbox Studio, Chicago with Corinne Mucha

Learning to speak quantum

Tue, 02/06/2018 - 16:27

Particle physicists are studying ways to harness the power of the quantum realm to further their research.

In a 1981 lecture, the famed physicist Richard Feynman wondered if a computer could ever simulate the entire universe. The difficulty with this task is that, on the smallest scales, the universe operates under strange rules: Particles can be here and there at the same time; objects separated by immense distances can influence each other instantaneously; the simple act of observing can change the outcome of reality.

“Nature isn’t classical, dammit,” Feynman told his audience, “and if you want to make a simulation of nature, you’d better make it quantum mechanical.”

Quantum computers

Feynman was imagining a quantum computer, a computer with bits that acted like the particles of the quantum world. Today, nearly 40 years later, such computers are starting to become a reality, and they pose a unique opportunity for particle physicists. 

“The systems that we deal with in particle physics are intrinsically quantum mechanical systems,” says Panagiotis Spentzouris, head of Fermilab’s Scientific Computing Division. “Classical computers cannot simulate large entangled quantum systems. You have plenty of problems that we would like to be able to solve accurately without making approximations that we hope we will be able to do on the quantum computer.”

Quantum computers allow for a more realistic representation of quantum processes. They take advantage of a phenomenon known as superposition, in which a particle such as an electron exists in a probabilistic state spread across multiple locations at once. 

Unlike a classical computer bit, which can be either on or off, a quantum bit—or qubit—can be on, off, or a superposition of both on and off, allowing for computations to be performed simultaneously instead of sequentially. 

This not only speeds up computations; it makes currently impossible ones possible. A problem that could effectively trap a normal computer in an infinite loop, testing possibility after possibility, could be solved almost instantaneously by a quantum computer. This processing speed could be key for particle physicists, who wade through enormous amounts of data generated by detectors. 

In the first demonstration of this potential, a team at CalTech recently used a type of quantum computer called a quantum annealer to “rediscover” the Higgs boson, the particle that, according to the Standard Model of particle physics, gives mass to every other fundamental particle. 

Scientists originally discovered the Higgs boson in 2012 using particle detectors at the Large Hadron Collider at CERN research center in Europe. They created Higgs bosons by converting the energy of particle collisions temporarily into matter. Those temporary Higgs bosons quickly decayed, converting their energy into other, more common particles, which the detectors were able to measure. 

Scientists identified the mass of the Higgs boson by adding up the masses of those less massive particles, the decay products. But to do so, they needed to pick out which of those particles came from the decay of Higgs bosons, and which ones came from something else. To a detector, a Higgs boson decay can look remarkably similar to other, much more common decays. 

LHC scientists trained a machine learning algorithm to find the Higgs signal against the decay background—the needle in the haystack. This training process required a huge amount of simulated data.

Physicist Maria Spiropulu, who was on the team that discovered the Higgs the first time around, wanted to see if she could improve the process with quantum computing. The group she leads at CalTech used a quantum computer from a company called D-Wave to train a similar machine learning algorithm. They found that the quantum computer trained the machine learning algorithm on a significantly smaller amount of data than the classical method required. In theory, this would give the algorithm a head start, like giving someone looking for the needle in the haystack expert training in spotting the glint of metal before turning their eyes to the hay. 

“The machine cannot learn easily,” Spiropulu says. “It needs huge, huge data. In the quantum annealer, we have a hint that it can learn with small data, and if you learn with small data you can use it as initial conditions later.”

Some scientists say it may take a decade or more to get to the point of using quantum computers regularly in particle physics, but until then they will continue to make advances to enhance their research.

Quantum sensors

Quantum mechanics is also disrupting another technology used in particle physics: the sensor, the part of a particle detector that picks up the energy from a particle interaction. 

In the quantum world, energy is discrete. The noun quantum means “a specific amount” and is used in physics to mean “the smallest quantity of energy.” Classical sensors generally do not make precise enough measurements to pick up individual quanta of energy, but a new type of quantum sensor can. 

“A quantum sensor is one that is able to sense these individual packets of energy as they arrive,” says Aaron Chou, a scientist at Fermilab. “A non-quantum sensor would not be able to resolve the individual arrivals of each of these little packets of energy, but would instead measure a total flow of the stuff.”

Chou is taking advantage of these quantum sensors to probe the nature of dark matter. Using technology originally developed for quantum computers, Chou and his team are building ultrasensitive detectors for a type of theorized dark matter particle known as an axion. 

“We’re taking one of the qubit designs that was previously created for quantum computing and we’re trying to use those to sense the presence of photons that came from the dark matter,” Chou says. 

For Spiropulu, these applications of quantum computers represent an elegant feedback system in the progression of technology and scientific application. Basic research in physics led to the initial transistors that fed the computer science revolution, which is now on the edge of transforming basic research in physics.

“You want to disrupt computing, which was initially a physics advance,” Spiropulu says. “Now we are using physics configurations and physics systems themselves to assist computer science to solve any problem, including physics problems.”

Sterile neutrino sleuths

Tue, 01/30/2018 - 17:14

Meet the detectors of Fermilab’s Short-Baseline Neutrino Program, hunting for signs of a possible fourth type of neutrino.

Neutrinos are not a sociable bunch. Every second, trillions upon trillions of the tiny particles shoot down to Earth from space, but the vast majority don’t stop in to pay a visit—they continue on their journey, almost completely unaffected by any matter they come across.

Their reluctance to hang around is what makes it such a challenge to study them. But the Short-Baseline Neutrino (SBN) Program at the US Department of Energy’s Fermilab is doing just that: further unraveling the mysteries of neutrinos with three vast detectors filled with ultrapure liquid argon.

Argon is an inert substance normally found in the air around us—and, once isolated, an excellent medium for studying neutrinos. A neutrino colliding with an argon nucleus leaves behind a signature track and a spray of new particles such as electrons or photons, which can be picked up inside a detector.

SBN uses three detectors along a straight line in the path of a specially designed neutrino source called the Booster Neutrino Beamline (BNB) at Fermilab. Scientists calculated the exact positions that would yield the most interesting and useful results from the experiment.

The detectors study a property of neutrinos that scientists have known about for a while but do not have a complete grasp on: oscillations, the innate ability of neutrinos to change their form as they travel. Neutrinos come in three known types, or “flavors”: electron, muon and tau. But oscillations mean each of those types is interchangeable with the others, so a neutrino that begins life as a muon neutrino can naturally transform into an electron neutrino by the end of its journey.

Some experiments, however, have come up with intriguing results that suggest there could be a fourth type of neutrino that interacts even less than the three types that have already been documented. An experiment at Los Alamos National Laboratory in 1995 showed the first evidence that a fourth neutrino might exist. It was dubbed the “sterile” neutrino because it appears to be unaffected by anything other than gravity. In 2007, MiniBooNE, a previous experiment at Fermilab, showed possible hints of its existence, too, but neither experiment was powerful enough to say if their results definitively demonstrated the existence of a new type of neutrino.   

That’s why it’s crucial to have these three, more powerful detectors. Carefully comparing the findings from all three detectors should allow the best measurement yet of whether a sterile neutrino is lurking out of sight. And finding the sterile neutrino would be evidence of new, intriguing physics—something that doesn’t fit our current picture of the world.

These three detectors are international endeavors, funded in part by DOE’s Office of Science, the National Science Foundation, the Science and Technology Facilities Council in the UK, CERN, the National Institute for Nuclear Physics (INFN) in Italy, the Swiss National Science Foundation and others. Each helps further develop the technologies, training and expertise needed to design, build and operate another experiment that has been under construction since July: the Deep Underground Neutrino Experiment (DUNE). This international mega-scientific collaboration hosted by Fermilab will send neutrinos 800 miles from Illinois to the massive DUNE detectors, which will be installed a mile underground at the Sanford Underground Research Facility in South Dakota.

Meet each of the SBN detectors below:

Artwork by Sandbox Studio, Chicago Short-Baseline Near Detector 

Closest to the BNB source at just 110 meters, the Short-Baseline Near Detector (SBND) provides a benchmark for the whole experiment, studying the neutrinos just after they leave the source and before they have a chance to oscillate between flavors. Almost a cube shape, the detecting part of the SBND is four meters tall and wide, five meters long and weighs around 260 tons in total—with a 112-ton active liquid argon volume. 

With a CERN-designed state-of-the-art membrane design for its cooling cryostat—which keeps the argon in a liquid state—SBND is a pioneering detector in the field of neutrino research. It will test new technologies and techniques that will be used in later neutrino projects such as DUNE.

Due to its proximity to the neutrino source, SBND will collect a colossal amount of interaction data. A secondary, long-term goal of SBND will be to work through this cache to precisely study the physics of these neutrino interactions and even to search for other signs of new physics.

“After a few years of running, we will have recorded millions of neutrino interactions in SBND, which will be a treasure trove of data that we can use to make many measurements,” says David Schmitz, physicist at the University of Chicago and co-spokesperson for the experiment. “Studying these neutrino interactions in this particular type of detector will have long-term value, especially in the context of DUNE, which will use the same detection principles.”

The SBND is well on its way to completion; its groundbreaking took place in April 2016 and its components are being built in Switzerland, the UK, Italy and at CERN.

Stats Detector name SBND (Short-Baseline Near Detector) Dimensions Almost cubic, 4x4x5m (5 meters in beam direction) Primary materials Cryostat and structure made from stainless steel, with polyurethane thermal insulation Argon mass 260 tons in total (112-ton active volume) Location 110 meters from BNB source Construction status Groundbreaking in April 2016, components currently being manufactured in universities and labs around the world What makes it unique Uses membrane cryostat technology, modular TPC construction, and sophisticated electronics operated at cryogenic temperatures, like that which will be used in DUNE; will record millions of neutrino interactions per year   Artwork by Sandbox Studio, Chicago MicroBooNE     

The middle detector, MicroBooNE, was the first of the three detectors to come online. When it did so in 2015, it was the first detector ever to collect data on neutrino interactions in argon at the energies provided by the BNB. The detector sits 360 meters past SBND, nestled as close as possible to its predecessor, MiniBooNE. This proximity is on purpose: MicroBooNE, a more advanced detector, is designed to get a better look at the intriguing results from MiniBooNE.

In all, MicroBooNE weighs 170 tons (with an active liquid argon volume of 89 tons), making it currently the largest operating neutrino detector in the United States of its kind—a Liquid Argon Time Projection Chamber (LArTPC). That title will transfer to the far detector, ICARUS (see below), upon its installation in 2018.

While following up on MiniBooNE’s anomaly, MicroBooNE has another important job: providing scientists at Fermilab with useful experience of operating a liquid argon detector, which contributes to the development of new technology for the next generation of experiments. 

“We’ve never in history had more than one liquid argon detector on any beamline, and that’s what makes the SBN Program exciting,” says Fermilab’s Sam Zeller, co-spokesperson for MicroBooNE. “It’s the first time we will have at least two detectors studying neutrino oscillations with liquid argon technology.” 

Techniques used to fill MicroBooNE with argon will pave the way for the gargantuan DUNE far detector in the future, which will hold more than 400 times as much liquid argon as MicroBooNE. Neutrino detectors rely on the liquid inside being extremely pure, and to achieve this goal, all the air normally has to be pumped out before liquid is put in. But MicroBooNE scientists used a different technique: They pumped argon gas into the detector—which pushed all the air out—and then cooled until it condensed into liquid. This new approach will eliminate the need to evacuate the air from DUNE’s six-story-tall detectors. 

Along with contributing to the next generation of detectors, MicroBooNE also contributes to training the next generation of neutrino scientists from around the world. Over half of the collaboration in charge of running MicroBooNE are students and postdocs who bring innovative ideas for analyzing its data.

Stats Detector name MicroBooNE (Micro Booster Neutrino Experiment) Dimensions Cylindrical shape (outer), inner TPC: 10.3m long x 2.3m tall x 2.5m wide Primary materials Stainless steel cylinder containing argon vessel and detector elements (stabilized with front and rear supports), polyurethane foam insulation on outer surfaces Argon mass 170 tons in total (89-ton active volume) Location 470 meters from BNB source Construction status Assembled at Fermilab 2012-13, installed in June 2014, has been operating since 2015 What makes it unique Used gas-pumped technique to fill with argon; more than half of operators are students or postdocs   Artwork by Sandbox Studio, Chicago ICARUS (Imaging Cosmic And Rare Underground Signals)

The largest of SBN’s detectors, ICARUS, is also the most distant from the neutrino source—600 meters down the line. Like SBND and MicroBooNE, ICARUS uses liquid argon as a neutrino detection technique, with over 700 tons of the dense liquid split between two symmetrical modules. These colossal tanks of liquid argon, together with excellent imaging capabilities, will allow extremely sensitive detections of neutrino interactions when the detector comes online at Fermilab in 2018.

The positioning of ICARUS along the neutrino beamline is crucial to its mission. The detector will measure the proportion of both electron and muon neutrinos that collide with argon nuclei as the intense beam of neutrinos passes through it. By comparing this data with that from SBND, scientists will be able to see if the results match with those from previous experiments and explore whether they could be explained by the existence of a sterile neutrino.

ICARUS, along with MicroBooNE, is also positioned on the Fermilab site close to another neutrino beam, called Neutrinos at the Main Injector (NuMI), which provides neutrinos for the existing experiments at Fermilab and in Minnesota. Unlike the main BNB beam, the NuMI beam will hit ICARUS at an angle through the detector. The goal will be to measure neutrino cross-sections—a measure of their interaction likelihood—rather than their oscillations. The energy of the NuMI beam is similar to that which will be used for DUNE, so ICARUS will provide excellent knowledge and experience to work out the kinks for the huge experiment.

The detector’s journey has been a long one. From its groundbreaking development, construction and operation in Italy at INFN’s Gran Sasso Laboratory under the leadership of Nobel laureate Carlo Rubbia, ICARUS traveled to CERN in Switzerland in 2014 for some renovation and upgrades. Equipped with new observing capabilities, it was then shipped across the Atlantic to Fermilab in 2017, where it is currently being installed in its future home. Scientists intend to begin taking data with ICARUS in 2018. 

“ICARUS unlocked the potential of liquid argon detectors, and now it’s becoming a crucial part of our research,” says Peter Wilson, head of Fermilab’s SBN program. “We’re excited to see the data coming out of our short-baseline neutrino detectors and apply the lessons we learn to better understand neutrinos with DUNE.”

Stats Detector name ICARUS (Imaging Cosmic And Rare Underground Signals) Dimensions Argon chamber split into two separate argon chambers, each 3.6m long, 3.9m high, 19.6m long Primary materials Detector components held by low-carbon stainless-steel structure, inside cryostat made of aluminum, with thermal shielding layers of boiling nitrogen (to maintain cryostat temperature) and polyurethane thermal insulation Argon mass 760 tons in total (476-ton active volume) Location 600 meters from BNB source Construction status Designed and built in the INFN lab in Pavia, Italy, from the late 1990s, then transferred to the INFN Underground Laboratory at Gran Sasso Laboratory, Italy, where it began operating in 2010. Traveled to CERN for refurbishment in 2014. Arrived at Fermilab in July 2017; currently under installation. Aims to start taking data in 2018. What makes it unique Largest neutrino liquid argon TPC ever built  


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Brown University animates science communication

Thu, 01/25/2018 - 17:03

The SciToons program pairs students with different levels of scientific expertise to create animated science explainers.

Once a week at Brown University, professors and students with backgrounds ranging from neuroscience to literary arts come together to collaborate. They're participating in a program called "SciToons," created in 2011 by Oludurotimi Adetunji, an adjunct assistant professor of physics and Brown's associate dean of undergraduate research and inclusive science. The program pairs "experts" with "novices" to search for the best way to combine scientific concepts and animation in a three- to five-minute YouTube video. 

"Many people have this perception that those who don't attend college or have a background in science can't understand things like quantum physics," says Aisha Keown-Lang, a senior at Brown double-majoring in biology and political science. "But it is really about the ability to communicate properly."

SciToons aims to reach an audience of students in high school and above, so the video teams must take into account that the viewers will not be aware of all the specialized language scientists use. This is where the mesh between expert and novice comes in; they communicate back and forth to make sure all information is not only scientifically accurate but also understandable for the presumably inexperienced audience. "They fill in each other's gaps," Adetunji says. 

Creating a SciToons video takes about six months. After brainstorming a topic, the teams must write a script. "This takes several months because every word is thoroughly thought through," says Torrey Truszkowski, a neuroscience graduate student at Brown. Both the expert and the novice must approve the script before the project moves into the next phase.

After developing the script, the writers hand the project over to the animators, who develop a storyboard and visuals. The experts and novices reconvene to discuss and give feedback on the result. 

Before uploading the final product to YouTube, all participants in the program—animators, professors, writers and students from all types of educational backgrounds—come together to ask the final question: "Does this work?" 

If their answer is yes, they hit publish and wait to see if their audience agrees. Some videos have struck a definite chord. The most popular SciToons video so far—"How do we see color?"—has reached over 145,000 views. 

"I was thinking narrowly with neuroscience, but now I see how I can apply myself in many different ways," Truszkowski says. She is now planning to pursue a career in science communications. 

 SciToons has also created an atmosphere for scholars to discuss and collaborate on topics outside their select fields of study, Adetunji says. This has allowed both novice and expert to deviate from the isolation in their personal career paths. 

Currently all members of SciToons are either students or professors at Brown, but Adetunji hopes to eventually include high school students and collaborators in the process as well. 

Neural networks for neutrinos

Tue, 01/23/2018 - 18:36

Scientists are using cutting-edge machine-learning techniques to analyze physics data.

Particle physics and machine learning have long been intertwined. 

One of the earliest examples of this relationship dates back to the 1960s, when physicists were using bubble chambers to search for particles invisible to the naked eye. These vessels were filled with a clear liquid that was heated to just below its boiling point so that even the slightest boost in energy—for example, from a charged particle crashing into it—would cause it to bubble, an event that would trigger a camera to take a photograph. 

Female scanners often took on the job of inspecting these photographs for particle tracks. Physicist Paul Hough handed that task over to machines when he developed the Hough transform, a pattern recognition algorithm, to identify them. 

The computer science community later developed the Hough transform for use in applications such as computer vision, attempts to train computers to replicate the complex function of a human eye. 

“There’s always been a little bit of back and forth” between these two communities, says Mark Messier, a physicist at Indiana University. 

Since then, the field of machine learning has rapidly advanced. Deep learning, a form of artificial intelligence modeled after the human brain, has been implemented for a wide range of applications such as identifying faces, playing video games and even synthesizing life-like videos of politicians

Over the years, algorithms that help scientists pick interesting aberrations out of background data have been used in physics experiments such as BaBar at SLAC National Accelerator Laboratory and experiments at the Large Electron-Positron Collider at CERN and the Tevatron at Fermi National Accelerator Laboratory. More recently, algorithms that learn to recognize patterns in large datasets have been handy for physicists studying hard-to-catch particles called neutrinos. 

This includes scientists on the NOvA experiment, who study a beam of neutrinos created at the US Department of Energy’s Fermilab near Chicago. The neutrinos stream straight through Earth to a 14,000-metric-ton detector filled with liquid scintillator sitting near the Canadian border in Minnesota.

When a neutrino strikes the liquid scintillator, it releases a burst of particles. The detector collects information about the pattern and energy of those particles. Scientists use that information to figure out what happened in the original neutrino event. 

“Our job is almost like reconstructing a crime scene,” Messier says. “A neutrino interacts and leaves traces in the detector—we come along afterward and use what we can see to try and figure out what we can about the identity of the neutrino.” 

Over the last few years, scientists have started to use algorithms called convolutional neural networks (CNNs) to take on this task instead. 

CNNs, which are modelled after the mammalian visual cortex, are widely used in the technology industry—for example, to improve computer vision for self-driving cars. These networks are composed of multiple layers that act somewhat like filters: They contain densely interconnected nodes that possess numerical values, or weights, that are adjusted and refined as inputs pass through. 

“The ‘deep’ part comes from the fact that there are many layers to it,” explains Adam Aurisano, an assistant professor at the University of Cincinnati. “[With deep learning] you can take nearly raw data, and by pushing it through these stacks of learnable filters, you wind up extracting nearly optimal features.” 

For example, these algorithms can extract details associated with particle interactions of varying complexity from the “images” collected by recording different patterns of energy deposits in particle detectors. 

“Those stacks of filters have sort of sliced and diced the image and extracted physically meaningful bits of information that we would have tried to reconstruct before,” Aurisano says.

Although they can be used to classify events without recreating them, CNNs can also be used to reconstruct particle interactions using a method called semantic segmentation. 

When applied to an image of a table, for example, this method would reconstruct the object by tagging each pixel associated with it, Aurisano explains. In the same way, scientists can label each pixel associated with characteristics of neutrino interactions, then use algorithms to reconstruct the event. 

Physicists are using this method to analyze data collected from the MicroBooNE neutrino detector. 

“The nice thing about this process is that you might find a cluster that’s made by your network that doesn’t fit in any interpretation in your model,” says Kazuhiro Terao, a scientist at SLAC National Accelerator Laboratory. “That might be new physics. So we could use these tools to find stuff that we might not understand.” 

Scientists working on other particle physics experiments, such as those at the Large Hadron Collider at CERN, are also using deep learning for data analysis.

“All these big physics experiments are really very similar at the machine learning level,” says Pierre Baldi, a computer scientist at the University of California, Irvine. “It's all images associated with these complex, very expensive detectors, and deep learning is the best method for extracting signal against some background noise.” 

Although most of the information is currently flowing from computer scientists to particle physicists, other communities may also gain new tools and insights from these experimental applications as well. 

For example, according to Baldi, one question that’s currently being discussed is whether scientists can write software that works across all these physics experiments with a minimal amount of human tuning. If this goal were achieved, it could benefit other fields, such a biomedical imaging, that use deep learning as well. “[The algorithm] would look at the data and calibrate itself,” he says. “That’s an interesting challenge for machine learning methods.” 

Another future direction, Terao says, would be to get machines to ask questions—or, more simply, to be able to identify outliers and try to figure out how to explain them. 

“If the AI can form a question and come up with a logical sequence to solve it, then that replaces a human,” he says. “To me, the kind of AI you want to see is a physics researcher—one that can do scientific research.”

First cryomodule for ultrapowerful X-ray laser arrives

Fri, 01/19/2018 - 19:15

A Fermilab team built and tested the first new superconducting accelerator cryomodule for SLAC’s LCLS-II project.

Earlier this week, scientists and engineers at the US Department of Energy’s Fermi National Accelerator Laboratory in Illinois loaded one of the most advanced superconducting radio-frequency cryomodules ever created onto a truck and sent it heading west.

Today, that cryomodule arrived at SLAC National Accelerator Laboratory in California, where it will become the first of 37 powering a 3-mile-long machine that will revolutionize atomic X-ray imaging. The modules are the product of many years of innovation in accelerator technology, and the first cryomodule Fermilab developed for this project set a world record in energy efficiency.

These modules, when lined up end to end, will make up the bulk of the accelerator that will power a massive upgrade to the capabilities of the Linac Coherent Light Source at SLAC, a unique X-ray microscope that will use the brightest X-ray pulses ever made to provide unprecedented details of the atomic world. Fermilab will provide 22 of the cryomodules, with the rest built and tested at Thomas Jefferson National Accelerator Facility in Virginia.

The quality factor achieved in these components is unprecedented for superconducting radio-frequency cryomodules. The higher the quality factor, the lower the cryogenic load, and the more efficiently the cavity imparts energy to the particle beam. Fermilab’s record-setting cryomodule doubled the quality factor compared to the previous state-of-the-art.

“LCLS-II represents an important technological step which demonstrates that we can build more efficient and more powerful accelerators,” says Fermilab Director Nigel Lockyer. “This is a major milestone for our accelerator program, for our productive collaboration with SLAC and Jefferson Lab and for the worldwide accelerator community.”

Today’s arrival is merely the first. From now into 2019, the teams at Fermilab and Jefferson Lab will build the remaining cryomodules, including spares, and scrutinize them from top to bottom, sending them to SLAC only after they pass the rigorous review.

“It’s safe to say that this is the most advanced machine of its type,” says Elvin Harms, a Fermilab accelerator physicist working on the project. “This upgrade will boost the power of LCLS, allowing it to deliver X-ray laser beams that are 10,000 times brighter than it can give us right now.”

With short, ultrabright pulses that will arrive up to a million times per second, LCLS-II will further sharpen our view of how nature works at the smallest scales and help advance transformative technologies of the future, including novel electronics, life-saving drugs and innovative energy solutions. Hundreds of scientists use LCLS each year to catch a glimpse of nature’s fundamental processes.

To meet the machine’s standards, each Fermilab-built cryomodule must be tested in nearly identical conditions as in the actual accelerator. Each large metal cylinder—up to 40 feet in length and 4 feet in diameter—contains accelerating cavities through which electrons zip at nearly the speed of light. But the cavities, made of superconducting metal, must be kept at a temperature of 2 Kelvin (minus 456 degrees Fahrenheit).

To achieve this, ultracold liquid helium flows through pipes in the cryomodule, and keeping that temperature steady is part of the testing process.

“The difference between room temperature and a few Kelvin creates a problem, one that manifests as vibrations in the cryomodule,” says Genfa Wu, a Fermilab scientist working on LCLS-II. “And vibrations are bad for linear accelerator operation.”

In initial tests of the prototype cryomodule, scientists found vibration levels that were higher than specification. To diagnose the problem, they used geophones—the same kind of equipment that can detect earthquakes—to rule out external vibration sources. They determined that the cause was inside the cryomodule and made a number of changes, including adjusting the path of the flow of liquid helium. The changes worked, substantially reducing vibration levels to a 10th of what they were originally, and have been successfully applied to subsequent cryomodules.

Fermilab scientists and engineers are also ensuring that unwanted magnetic fields in the cryomodule are kept to a minimum, since excessive magnetic fields reduce the operating efficiency.

“At Fermilab, we are building this machine from head to toe,” Lockyer says. “From nanoengineering the cavity surface to the integration of thousands of complex components, we have come a long way to the successful delivery of LCLS-II’s first cryomodule.”

Fermilab has tested seven cryomodules, plus one built and previously tested at Jefferson Lab, with great success. Each of those, along with the modules yet to be built and tested, will get its own cross-country trip in the months and years to come.

Editor's note: This article is based on a Fermilab press release.

The biggest little detectors

Thu, 01/18/2018 - 21:34

The ProtoDUNE detectors for the Deep Underground Neutrino Experiment are behemoths in their own right.

In one sense, the two ProtoDUNE detectors are small. As prototypes of the much larger planned Deep Underground Neutrino Experiment, they are only representative slices, each measuring about 1 percent of the size of the final detector. But in all other ways, the ProtoDUNE detectors are simply massive.

Once they are complete later this year, these two test detectors will be larger than any detector ever built that uses liquid argon, its active material. The international project involves dozens of experimental groups coordinating around the world. And most critically, the ProtoDUNE detectors, which are being installed and tested at the European particle physics laboratory CERN, are the rehearsal spaces in which physicists, engineers and technicians will hammer out nearly every engineering problem confronting DUNE, the biggest international science project ever conducted in the United States.

Gigantic detector, tiny neutrino

DUNE’s mission, when it comes online in the mid-2020s, will be to pin down the nature of the neutrino, the most ubiquitous particle of matter in the universe. Despite neutrinos’ omnipresence—they fill the universe, and trillions of them stream through us every second—they are a pain in the neck to capture. Neutrinos are vanishingly small, fleeting particles that, unlike other members of the subatomic realm, are heedless of the matter through which they fly, never stopping to interact.

Well, almost never.

Once in a while, scientists can catch one. And when they do, it might tell them a bit about the origins of the universe and why matter predominates over antimatter—and thus how we came to be here at all.

A global community of more than 1000 scientists from 31 countries are building DUNE, a megascience experiment hosted by the Department of Energy’s Fermi National Accelerator Laboratory. The researchers’ plan is to observe neutrinos using two detectors separated by 1300 kilometers—one at Fermilab outside Chicago and a second one a mile underground in South Dakota at the Sanford Underground Research Facility. Having one at each end enables scientists to see how neutrinos transform as they travel over a long distance.

The DUNE collaboration is going all-in on the bigger-is-better strategy; after all, the bigger the detector, the more likely scientists are to snag a neutrino. The detector located in South Dakota, called the DUNE far detector, will hold 70,000 metric tons (equivalent to about 525,000 bathtubs) of liquid argon to serve as the neutrino fishing net. It comprises four large modules. Each will stand four stories high and, not including the structures that house the utilities, occupy a footprint roughly equal to a soccer field.

In short, DUNE is giant.

Small Particles, Big Science: The International LBNF/DUNE Project Video of Small Particles, Big Science: The International LBNF/DUNE Project Lots of room in ProtoDUNE

The ProtoDUNE detectors are small only when compared to the giant DUNE detector. If each of the four DUNE modules is a 20-room building, then each ProtoDUNE detector is one room.

But one room large enough to envelop a small house.

As one repeatable unit of the ultimate detector, the ProtoDUNE detectors are necessarily big. Each is an enormous cube—about two stories high and about as wide—and contains about 800 metric tons of liquid argon.

Why two prototypes? Researchers are investigating two ways to use argon and so are constructing two slightly different but equally sized test beds. The single-phase ProtoDUNE uses only liquid argon, while the dual-phase ProtoDUNE uses argon as both a liquid and a gas.

“They’re the largest liquid-argon particle detectors that have ever been built,” says Ed Blucher, DUNE co-spokesperson and a physicist at the University of Chicago.

As DUNE’s test bed, the ProtoDUNE detectors also have to offer researchers a realistic picture of how the liquid-argon detection technology will work in DUNE, so the instrumentation inside the detectors is also at full, giant scale.

“If you’re going to build a huge underground detector and invest all of this time and all of these resources into it, that prototype has to work properly and be well-understood,” says Bob Paulos, director of the University of Wisconsin–Madison Physical Sciences Lab and a DUNE engineer. “You need to understand all the engineering problems before you proceed to build literally hundreds of these components and try to transport them all underground.”

A crucial step for ProtoDUNE was welding together the cryostat, or cold vessel, that will house the detector components and liquid argon.

Photo by CERN Partners in ProtoDUNE

ProtoDUNE is a rehearsal for DUNE not only in its technical orchestration but also in the coordination of human activity.

When scientists were planning their next-generation neutrino experiment around 2013, they realized that it could succeed only by bringing the international scientific community together to build the project. They also saw that even the prototyping would require an effort of global proportions—both geographically and professionally. As a result, DUNE and ProtoDUNE actively invite students, early-career scientists and senior researchers from all around the world to contribute.

“The scale of ProtoDUNE, a global collaboration at CERN for a US-based megaproject, is a paradigm change in the way neutrino science is done,” says Christos Touramanis, a physicist at the University of Liverpool and one of the co-coordinators of the single-phase detector. For both DUNE and ProtoDUNE, funding comes from partners around the world, including the Department of Energy's Office of Science and CERN.

The successful execution of ProtoDUNE’s assembly and testing by international groups requires a unity of purpose from parties that could hardly be farther apart, geographically speaking.

Scientists say the effort is going smoothly.

“I’ve been doing neutrino physics and detector technology for the last 20 or 25 years. I’ve never seen such an effort go up so nicely and quickly. It’s astonishing,” says Fermilab scientist Flavio Cavanna, who co-coordinates the single-phase ProtoDUNE project. “We have a great collaboration, great atmosphere, great willingness to make it. Everybody is doing his or her best to contribute to the success of this big project. I used to say that ProtoDUNE was mission impossible, because—in the short time we were given to make the two detectors, it looked that way in the beginning. But looking at where we are now, and all the progress made so far, it starts turning out to be mission possible.”

The anode plane array (APA) is prepped for shipment at Daresbury Laboratory in the UK.

Christos Touramanis Inside the liquid-argon test bed

So how do neutrino liquid-argon detectors work? Most of the space inside serves as the arena of particle interaction, where neutrinos can smash into an argon atom and create secondary particles. Surrounding this interaction space is the instrumentation that records these rare collisions, like a camera committing the scene to film. DUNE collaborators are developing and constructing the recording instruments that will capture the evidence of these interactions.

One signal is ionization charge: A neutrino interaction generates other particles that propagate through the detector’s vast argon pool, kicking electrons—called ionization electrons—off atoms as they go. The second signal is light.

Animation: Neutrino Detection in Liquid-Argon Time Projection Chamber Video of Animation: Neutrino Detection in Liquid-Argon Time Projection Chamber

The first signal emerges as a streak of ionization electrons.

To record the signal, scientists will use something called an anode plane array, or APA. An APA is a screen created using 24 kilometers of precisely tensioned, closely spaced, continuously wound wire. This wire screen is positively charged, so it attracts the negatively charged electrons.

Much the way a wave front approaches the beach’s shore, the particle track—a string of the ionization electrons—will head toward the positively charged wires inside the ProtoDUNE detectors. The wires will send information about the track to computers, which will record its properties and thus information about the original neutrino interaction.

A group in the University of Wisconsin–Madison Physical Sciences Lab led by Paulos designed the single-phase ProtoDUNE wire arrays. The Wisconsin group, Daresbury Laboratory in the UK and several UK universities are building APAs for the same detector. The first APA from Wisconsin arrived at CERN last year; the first from Daresbury Lab arrived earlier this week.

“These are complicated to build,” Paulos says, noting that it currently takes about three months to build just one. “Building these 6-meter-tall anode planes with continuously wound wire—that’s something that hasn't been done before.”

ProtoDUNE Anode Plane Assembly Video of ProtoDUNE Anode Plane Assembly

The anode planes attract the electrons. Pushing away the electrons will be a complementary set of panels, called the cathode plane. Together, the anode and cathode planes behave like battery terminals, with one repelling electron tracks and the other drawing them in. A group at CERN designed and is building the cathode plane.

The dual-phase detector will operate on the same principle but with a different configuration of wire arrays. A special layer of electronics near the cathode will allow for the amplification of faint electron tracks in a layer of gaseous argon. Groups at institutions in France, Germany and Switzerland are designing those instruments. Once complete, they will also send their arrays to be tested at CERN.

Then there’s the business of observing light.

The flash of light is the result of a release of energy from the electron in the process of getting bumped from an argon atom. The appearance of light is like the signal to start a stopwatch; it marks the moment the neutrino interaction in a detector takes place. This enables scientists to reconstruct in three dimensions the picture of the interaction and resulting particles.

On the other side of the equator, a group at the University of Campinas in Brazil is coordinating the installation of instruments that will capture the flashes of light resulting from particle interactions in the single-phase ProtoDUNE detector.

Two of the designs for the single-phase prototype—one by Indiana University, the other by Fermilab and MIT—are of a type called guiding bars. These long, narrow strips work like fiber optic cables: they capture the light, convert it into light in the visible spectrum and finally guide it to an external sensor.

A third design, called ARAPUCA, was developed by three Brazilian universities and Fermilab and is being partially produced at Colorado State University. Named for the Guaraní word for a bird trap, the efficient ARAPUCA design will be able to “trap” even very low light signals and transmit them to its sensors.

The ARAPUCA array, designed by three Brazilian universities and Fermilab, was partially produced at Colorado State University.

D. Warner, Colorado State University

“The ARAPUCA technology is totally new,” says University of Campinas scientist Ettore Segreto, who is co-coordinating the installation of the light detection systems in the single-phase prototype. “We might be able to get more information from the light detection—for example, greater energy resolution.”

Groups from France, Spain and the Swiss Federal Institute of Technology are developing the light detection system for the dual-phase prototype, which will comprise 36 photomultiplier tubes, or PMTs, situated near the cathode plane. A PMT works by picking up the light from the particle interaction and converting it into electrons, multiplying their number and so amplifying the signal’s strength as the electrons travel down the tube.

With two tricked-out detectors, the DUNE collaboration can test their picture-taking capabilities and prepare DUNE to capture in exquisite detail the fleeting interactions of neutrinos.

Bringing instruments into harmony

But even if they’re instrumented to the nines inside, two isolated prototypes do not a proper test bed make. Both ProtoDUNE detectors must be hooked up to computing systems so particle interaction signals can be converted into data. Each detector must be contained in a cryostat, which functions like a thermos, for the argon to be cold enough to maintain a liquid state. And the detectors must be fed particles in the first place.

CERN is addressing these key areas by providing particle beam, innovative cryogenics and computing infrastructures, and connecting the prototype detectors with the DUNE experimental environment.

DUNE’s neutrinos will be provided by the Long-Baseline Neutrino Facility, or LBNF, which held an underground groundbreaking for the start of its construction in July. LBNF, led by Fermilab, will provide the construction, beamline and cryogenics for the mammoth DUNE detector, as well as Fermilab’s chain of particle accelerators, which will provide the world’s most intense neutrino beam to the experiment.

CERN is helping simulate that environment as closely as possible with the scaled-down ProtoDUNE detectors, furnishing them with particle beams so researchers can characterize how the detectors respond. Under the leadership of scientist Marzio Nessi, last year the CERN group built a new facility for the test beds, where CERN is now constructing two new particle beamlines that extend the lab’s existing network.

The recently arrived anode plane array (hanging on the left) is moved by a crane to its new home in the ProtoDUNE cryostat.

Photo by CERN

In addition, CERN built the ProtoDUNE cryostats—the largest ever constructed for a particle physics experiment—which also will serve as prototypes for those used in DUNE. Scientists will be able to gather and interpret the data generated from the detectors with a CERN computing farm and software and hardware from several UK universities.

“The very process of building these prototype detectors provides a stress test for building them in DUNE,” Blucher says.

CERN’s beam schedule sets the schedule for testing. In December, the European laboratory will temporarily shut off beam to its experiments for upgrades to the Large Hadron Collider. DUNE scientists aim to position the ProtoDUNE detectors in the CERN beam before then, testing the new technologies pioneered as part of the experiment.

“ProtoDUNE is a necessary and fundamental step towards LBNF/DUNE,” Nessi says. “Most of the engineering will be defined there and it is the place to learn and solve problems. The success of the LBNF/DUNE project depends on it.”

Voyage into the dark sector

Tue, 01/16/2018 - 18:58

A hidden world of particles awaits.

We don’t need extra dimensions or parallel universes to have an alternate reality superimposed right on top of our own. Invisible matter is everywhere. 

For example, take neutrinos generated by the sun, says Jessie Shelton, a theorist at the University of Illinois at Urbana-Champaign who works on dark sector physics. “We are constantly bombarded with neutrinos, but they pass right through us. They share the same space as our atoms but almost never interact.”

As far as scientists can tell, neutrinos are solitary particles. But what if there is a whole world of particles that interact with one another but not with ordinary atoms? This is the idea behind the dark sector: a theoretical world of matter existing alongside our own but invisible to the detectors we use to study the particles we know.

“Dark sectors are, by their very definition, built out of particles that don't interact strongly with the Standard Model,” Shelton says.

The Standard Model is a physicist’s field guide to the 17 particles and forces that make up all visible matter. It explains how atoms can form and why the sun shines. But it cannot explain gravity, the cosmic imbalance of matter and antimatter, or the disparate strengths of nature's four forces.

On its own, an invisible world of dark sector particles cannot solve all these problems. But it certainly helps.

Artwork by Sandbox Studio, Chicago with Ana Kova

The main selling point for the dark sector is that the theories comprehensively confront the problem of dark matter. Dark matter is a term physicists coined to explain bizarre gravitational effects they observe in the cosmos. Distant starlight appears to bend around invisible objects as it traverses the cosmos, and galaxies spin as if they had five times more mass than their visible matter can explain. Even the ancient light preserved in cosmic microwave background seems to suggest that there is an invisible scaffolding on which galaxies are formed.

Some theories suggest that dark matter is simple cosmic debris that adds mass—but little else—to the complexity of our cosmos. But after decades of searching, physicists have yet to find dark matter in a laboratory experiment. Maybe the reason scientists haven’t been able to detect it is that they’ve been underestimating it.

“There is no particular reason to expect that whatever is going on in the dark sector has to be as simple as our most minimal models,” Shelton says. “After all, we know that our visible world has a lot of rich physics: Photons, electrons, protons, nuclei and neutrinos are all critically important for understanding the cosmology of how we got here. The dark sector could be a busy place as well.”

According to Shelton, dark matter could be the only surviving particle out of a similarly complicated set of dark particles.

“It could even be something like the proton, a bound state of particles interacting via a very strong dark force. Or it could even be something like a hydrogen atom, a bound state of particles interacting via a weaker dark force,” she says.

Even if terrestrial experiments cannot see these stable dark matter particles directly, they might be sensitive to other kinds of dark particles, such as dark photons or short-lived dark particles that interact strongly with the Higgs boson.

“The Higgs is one of the easiest ways for the Standard Model particles to talk to the dark sector,” Shelton says.

As far as scientists know, the Higgs boson is not picky. It may very well interact will all sorts of massive particles, including those invisible to ordinary atoms. If the Higgs boson interacts with massive dark sector particles, scientists should find that its properties deviate slightly from the Standard Model’s predictions. Scientists at the Large Hadron Collider are precisely measuring the properties of the Higgs boson to search for unexpected quirks that could open a gateway to new physics.

At the same time, scientists are also using the LHC to search for dark sector particles directly. One theory is that at extremely high temperatures, dark matter and ordinary matter are not so different and can transform into one another through a dark force. In the hot and dense early universe, this would have been quite common.

“But as the universe expanded and cooled, this interaction froze out, leaving some relic dark matter behind,” Shelton says.

The energetic particle collisions generated by the LHC imitate the conditions that existed in the early universe and could unlock dark sector particles. If scientists are lucky, they might even catch dark sector particles metamorphosing into ordinary matter, an event that could materialize in the experimental data as particle tracks that suddenly appear from no apparent source. 

But there are also several feasible scenarios in which any interactions between the dark sector and our Standard Model particles are so tiny that they are out of reach of modern experiments, according to Shelton.

"These ‘nightmare’ scenarios are completely logical possibilities, and in this case, we will have to think very carefully about astrophysical and cosmological ways to look for the footprints of dark particle physics,” she says.

Even if the dark sector is inaccessible to particle detectors, dark matter will always be visible through the gravitational fingerprint it leaves on the cosmos.

“Gravity tells us a lot about how much dark matter is in the universe and the kinds of particle interactions dark sector particles can and cannot have,” Shelton says. “For instance, more sensitive gravitational-wave experiments will give us the possibility to look back in time and see what our universe looked like at extremely high energies, and could maybe reveal more about this invisible matter living in our cosmos.”

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Rivers in the sky

Wed, 01/10/2018 - 18:52

Local communities named newly discovered stellar streams for bodies of water close to home.

Most of the time, the Dark Energy Camera in Chile stares out into the deepest regions of space, measuring light from distant galaxies. But this gigantic eye sometimes discovers things closer to home—like the 11 newly found stellar streams that the Dark Energy Survey announced today. For a few lucky groups in Chile and Australia, this meant an extraordinary opportunity: getting to name an object in space.

“The people were very enthusiastic,” says Kyler Kuehn, a scientist with the Dark Energy Survey who coordinated the outreach effort in Australia. “I don’t know if they are aware how rarely people get to name things that are newly discovered in space—or anywhere, for that matter—but I was pretty excited about it."

Stellar streams are ribbons of stars orbiting a galaxy (in this case, our own Milky Way). These faint filaments are the remnants of dwarf galaxies or star clusters that have been ripped apart by the gravity of their monster neighbor. Unlike some celestial objects that have very specific naming conventions according to the International Astronomical Union, stellar streams have a bit of flexibility.

Previously discovered stellar streams were often named after constellations in the sky near their location—but with many streams often appearing close to one another and other objects such as dwarf galaxies using the same convention, things became messy. Carl Grillmair, a CalTech astronomer studying stellar streams, proposed using the names of rivers in Greek mythology, like the River Styx. From there, naming expanded into real-world rivers.

DES decided to go the terrestrial route. One set of stellar streams, located in the sky near the Indus constellation, received names of Indian rivers: Indus, Jhelum, Chenab and Ravi. The collaboration decided to name the other two groups of streams after native words relating to water or rivers in Chile, where the Dark Energy Camera is located at the Cerro Tololo Inter-American Observatory, and Australia, where the Anglo-Australian Telescope is often used to follow up on those DECam discoveries.

Photo by Yeimy Vargas, Colegio Antonio Varas

In Chile, DES worked with students in the nearby town of Vicuña. High school students Dánae Rojas and Emerson Carvajal researched words from the native Quechua and Aymara cultures that were related to water, then presented several options to about 90 kindergarten and first-grade students. Their final selections were the Aymara name Aliqa Una, meaning Quiet Water, and two Quechua names, Palca, meaning Crossing Rivers, and Willka Yaku, or Sacred Water. Two Spanish names for local rivers near Vicuña, Elqui and Turbio, rounded out the set.

“It was absolutely wonderful to get the community involved in this process,” says Alfredo Zenteno, a DES scientist who, along with Kathy Vivas, led the outreach effort in Chile. “It is a way to make these new discoveries, which were made with a telescope in the region, close to them. For us, the astronomers, it is a way to thank the region that hosts the telescope and allows us to investigate the sky,”

In Australia, Kuehn worked with an Aboriginal storyteller and tribal elders to pick culturally sensitive and appropriate names in native languages.

“I wanted to honor the long history of aboriginal Australians doing astronomy,” Kuehn says. “Today's Aboriginal populations are the caretakers of some of the oldest continuous cultures on the planet, and their collective knowledge—including astronomical observations—date back tens of thousands of years.”

With a list of half a dozen names, Kuehn presented to a group of about 100 raucous adults at the Sydney Royal Botanic Gardens and 40 polite preschoolers, asking them to cheer to select their favorites. The Australian-named stellar streams are Wambelong, meaning Crazy Water in the Gamilaraay language, and Turranburra, the Dharug name for the Lane Cove River that runs near the headquarters of the Australian Astronomical Observatory. Scientists hope the names build connections between the nations that host the observatories and the discoveries they make about the universe that hosts us all. 

“It was wonderful to see the community have a chance to write in the sky,” Zenteno says.

Editor's note: You can learn more about the stellar streams and the accompanying release of three years of data from the Dark Energy Survey's lead lab, Fermilab.

Not an ugly sweater party

Thu, 12/21/2017 - 19:56

University College London scientists make physics festive with sweaters and songs at their annual holiday gathering.

Every year, postdocs in high-energy physics at University College London are asked to give a short, light-hearted talk about their research for the holidays.

Louie Corpe, a UCL scientist on the ATLAS experiment at the Large Hadron Collider, says he had heard about some “fairly elaborate” presentations from previous years, including one given in the form of a Christmas carol.

“I’m a little competitive by nature,” he wrote in an email. “That’s where the idea of the Xmas jumper presentation came about.”

He converted two plots and a Feynman diagram into cross-stitch patterns for his talk on the topic of “exotic searches for long-lived particles,” which he gave wearing a sweater embroidered with an ATLAS event display—the handiwork of his fiancée, Emma.

“In particular, we are looking for displaced jets which decay in the ATLAS HCAL,” he wrote. “The jumper I was wearing described the topology we were looking for… The results of the analysis are not public yet, but I doubt anyone would be able to extract any useful information from my cross-stitched plot.”

Although he scored compliments for his outfit on social media, Corpe was not the winner of this year’s event. That honor went to postdoc Cheryl Patrick, who wrote and performed a five-song musical about her neutrinoless double beta decay experiment, SuperNEMO, with her PhD students singing back-up.

SuperNEMO The Musical Video of SuperNEMO The Musical

The 12 Days of Physicsmas

Thu, 12/21/2017 - 19:14

Add some science to your holiday carols.

There are plenty of songs about snow, decking the halls and holiday cheer—but where are the festive songs of science? For those singers who prefer curling up by the Bunsen burner (or a fiery ball of quark-gluon plasma) instead of the fireplace, Symmetry presents a new carol for your repertoire: “The 12 Days of Physicsmas.”

The 12 Days of Physicsmas Video of The 12 Days of Physicsmas

Lyrics to sing along:

On the 12th day of Physicsmas

My true love sent to me:

Twelve theorists thinking,

Eleven students coding,

Ten protons smashing,

Nine muons spinning,

Eight gluons gluing,

Seven beamlines beaming,

Six quarks combining,

Five sigma results,

Four Nobel Prizes,

Three neutrinos,

Two neutron stars,

And a grand unified theory.


Happy holidays from the Symmetry team!

Machine evolution

Tue, 12/19/2017 - 17:42

Planning the next big science machine requires consideration of both the current landscape and the distant future.

Around the world, there’s an ecosystem of large particle accelerators where physicists gather to study the most intricate details of matter. 

These accelerators are engineering marvels. From planning to construction to operation to retirement, their lifespans stretch across decades. 

But to get the most out of their investments of talent and funding, laboratories planning such huge projects have to think even longer-term: What could these projects become in their next lives? 

The following examples show how some of the world’s big physics machines have evolved to stay at the forefront of science and technology.

Same tunnel, new collisions

Before CERN research center in Geneva, Switzerland, had its Large Hadron Collider, it had the Large Electron-Positron Collider. LEP was the largest electron-positron collider ever built, occupying a nearly 17-mile circular tunnel dug beneath the border of Switzerland and France. The tunnel took three years to completely excavate and build. 

The first particle beam traveled around the LEP circular collider in 1989. Long before then, the international group of CERN physicists and engineers were already thinking about what CERN’s next machine could be. 

“People were saying, ‘Well, if we do build LEP, then we should make it compatible with the [then-proposed] Large Hadron Collider,’” says James Gillies, a senior communications advisor and member of the strategic planning and evaluation unit at CERN. “If you want to have a future facility, you often have to engage the people who just finished designing one machine to start thinking about the next one.”

LEP’s designers chose an energy for the collider that would mass-produce Z bosons, fundamental particles discovered by earlier experiments at CERN. The LHC would be a step up from LEP, reaching higher energies that scientists hoped could produce the Higgs boson. In the 1960s, theorists proposed the Higgs as a way to explain the origin of the mass of elementary particles. And the new machine to look for it could be built in the same 17-mile tunnel excavated for LEP.  

Engineers began working on the LHC while LEP was still running. The new machine required enlargements to underground areas—it needed bigger detectors and new experimental halls. 

“That was challenging because these caverns are huge. As they were being excavated, the pressure on the LEP tunnel was reduced and the LEP beamline needed realignment,” Gillies says. “So you constantly had to realign the collider for experiments as you were digging.” 

After LEP reached its highest energy in 2000, it was switched off. The tunnel remained the same, says Gillies, but there were many other changes. Only one of the LEP detectors, DELPHI, remains underground at CERN as a visitors’ point. 

In 2012, LHC scientists announced the discovery of the long-sought Higgs boson. The LHC is planned to continue running until at least 2035, gradually increasing the intensity of its particle collisions. The research and development into the accelerator’s successor is already happening. The possibilities include a higher energy LHC, a compact linear collider or an even larger circular collider.

Large Electron-Positron Collider

Location: CERN—Geneva, Switzerland

First beam: 1989

Link to LEP Timeline: Timeline

Courtesy of CERN Large Hadron Collider

Location: CERN—Geneva, Switzerland

First beam: 2008

Link to LHC Timeline: Timeline 

Courtesy of CERN High-powered science

Decades before the LHC came into existence, a suburb of Chicago was home to the most powerful collider in the world: the Tevatron. A series of accelerators at Fermi National Accelerator Laboratory boosted protons and antiprotons to nearly the speed of light. In the final, 4-mile Tevatron ring, the particles reached record energy levels, and more than 1000 superconducting magnets steered them into collisions. Physicists used the Tevatron to make the first direct measurement of the tau neutrino and to discover the top quark, the last observed lepton and quark, respectively, in the Standard Model.

The Tevatron shut down in 2011 after the LHC came up to speed, but the rest of Fermilab’s accelerator infrastructure was still hard at work powering research in particle physics—particularly on the abundant, mysterious and difficult-to-detect neutrino. 

Starting in 1999, a brand-new, 2-mile circular accelerator called the Main Injector was added to the Fermilab complex to increase the number of Tevatron particle collisions tenfold. It was joined in its tunnel by the Recycler, a permanent magnet ring that stored and cooled antiprotons. 

But before the Main Injector was even completed, scientists had identified a second purpose: producing powerful beams of neutrinos for experiments in Illinois and 500 miles away in Minnesota. By 2005, the proton beam circulating in the Main Injector was doing double duty: sending ever-more-intense beams to the Tevatron collider and smashing into a target to produce neutrinos. Following the shutdown of the Tevatron, the Recycler itself was recycled to increase the proton beam power for neutrino research.

“I’m still amazed at how we are able to use the Recycler. It can be difficult to transition if a machine wasn’t originally built for that purpose,” says Ioanis Kourbanis, the head of the Main Injector department at Fermilab. 

Fermilab’s high-energy neutrino beam is already the most intense in the world, but the laboratory plans to enhance it with future improvements to the Main Injector and the Recycler, and to build a brand-new neutrino beamline. 

Neutrinos almost never interact with matter, so they can pass straight through the Earth on their way to detectors onsite and others several hundred miles away. Scientists hope to learn more about neutrinos and their possible role in shaping our early universe.

The new beamline will be part of the Long-Baseline Neutrino Facility, which will send neutrinos 800 miles underground to the massive, mile-deep detectors of the Deep Underground Neutrino Experiment. Scientists from around the world will use the DUNE data to answer questions about neutrinos, thanks to the repurposed pieces of the Fermilab accelerator complex.


Location: Fermilab—Batavia, Illinois

First beam: 1983

Link to Tevatron Timeline: Timeline 

Courtesy of Fermilab Neutrinos at the Main Injector (NuMI) beam

Location: Fermilab—Batavia, Illinois

First beam: 2004

Link to Fermilab Timeline: Timeline

Courtesy of Fermilab A monster accelerator

When physicists first came up with the idea to build a two-mile linear accelerator at what is now called SLAC National Accelerator Laboratory, managed by Stanford University, they called it "Project M” for “Monster.” Engineers began building it from hand-drawn designs. Once completed, the machine was able to accelerate electrons to near the speed of light, producing its first particle beam in May 1966. 

The accelerator’s scientific purpose has gone through several iterations of particle physics experiments over the decades, from fixed-target experiments to the Stanford Linear Collider (the only electron-positron linear collider ever built) to an injector for a circular collider, the Positron-Electron Project. 

These experiments led to the discovery that protons are made of quarks, the first evidence that the charm quark existed (through observations of the J/psi particle, co-discovered with researchers at MIT) and the discovery of the tau lepton. 

In 2009, the lab used the accelerator as the backbone for a different type of science machine—an X-ray free-electron laser, the Linac Coherent Light Source. 

“Looking around, SLAC was the only place in the world with a linear accelerator capable of driving a free-electron laser,” says Claudio Pellegrini, a distinguished professor emeritus of physics at the University of California, Los Angeles and a visiting scientist and consulting professor at SLAC. Pellegrini first proposed the idea to transform SLAC’s linear accelerator.

The new machine, a DOE Office of Science user facility, would be the world’s first laser of its kind that could produce extremely bright hard X-rays, the high-energy X-rays that let scientists take snapshots of atoms and molecules. 

“Much of the physics and many of the tools learned and developed during the operation of the Stanford Linear Collider were directly applicable to the free electron laser,” says Lia Merminga, head of the accelerator directorate at SLAC. “This was a big factor in the LCLS being commissioned in record time. Without the Stanford Linear Collider experience, this significant body of work would have to be reinvented and reproduced almost from scratch.”

Little about the accelerator itself needed to change. But to create a free-electron laser, scientists needed to design a new part: an electron gun, a device that generates electrons to be injected into the accelerator. A collaboration of several national labs and UCLA created a new type of electron gun for LCLS, while other national labs helped build undulators, a series of magnets that would wiggle the electrons to create X-rays.

LCLS used only the last third of SLAC’s original linear accelerator. In part of the remaining section, scientists are developing plasma wakefield and other new particle acceleration techniques.

For the X-ray laser’s next iteration, LCLS-II, scientists are aiming for an even brighter laser that will fire 1 million pulses per second, allowing them to observe rare and exceptionally transient events. 

To do this, they will need to replace the original copper structures with superconducting technology. The technology is derived from designs for a large International Linear Collider proposed to be built in Japan.

“I’m in awe of the foresight of the original builders of SLAC’s linear accelerator,” Merminga adds. “We’ve been able to do so much with this machine, and the end is not yet in sight.” 

Fixed target and collider experiments

Location: SLAC—Menlo Park, California

First beam: 1966

Link to SLAC Timeline: Timeline 

Courtesy of SLAC Linac Coherent Light Source

Location: SLAC—Menlo Park, California

First beam: 2009

Link to SLAC Timeline: Timeline 

Courtesy of SLAC

A trip into totality

Fri, 12/15/2017 - 18:59

This summer, physics students were offered a unique opportunity to study cosmic rays during the total solar eclipse.

August’s Great American Eclipse brought at least a partial eclipse to most of the United States, and 14 states experienced totality, a phenomenon that occurs when the sun is completely eclipsed by the moon. Eight Illinois high school students and five of their teachers traveled into the zone of totality to witness the two to three breathtaking minutes when the moon completely blocked the sun.

However, unlike most sky-watchers on August 21, these students did more than just marvel at the eclipse: They studied it, hoping to learn something about the effects of the sun going dark. Their mission? To measure whether the eclipse changed the number of detected cosmic rays—particles from space that rain down on Earth—which could tell us something about where these cosmic rays come from.

“This was a real scientific question high school students have the opportunity to answer,” says Nate Unterman, an emeritus teacher at Glenbrook North High School. “The students came up with a very elegant, scientific hypothesis: The cosmic ray flux will change during an eclipse.”

Unterman and another Glenbrook North teacher, Tony Valsamis, came up with the idea to study cosmic rays during the eclipse at an American Association of Physics Teachers conference, and they knew where to look for researchers: The school’s cosmic ray club.

Students in the school’s cosmic ray club had already been studying the behavior of cosmic rays, which reach Earth’s surface as muons—particles that are similar to electrons—using small-scale detectors provided by QuarkNet, a program designed to give students and teachers opportunities to get involved with high-energy physics research.

Unterman and Valsamis recognized these same detectors could be used during the eclipse to see whether the number of muons reaching Earth would change—something no study has measured from the ground.

“I got a call from Mr. Unterman while he was at the AAPT conference telling me about this idea to study the eclipse,” says Clarissa Carr, a Glenbrook North student and participant in the cosmic ray club. “I was immediately on board.”

The path to totality 

Four days before the eclipse, the research team, which consisted of students and teachers from Glenbrook North and Ida Crown Jewish Academy, made a five-hour trek from the Chicago area to Jefferson College in Hillsboro, Missouri.

“I drove a school bus with three students in it,” Valsamis says. “The rest of it was full of detectors, mounts and electronics.”

David Wang, Jacob Miller, Masha Matten, Clarissa Carr, Tamar Dallal, Allen Sears, Jacob Rosenberg and Ezra Schur pose in front of the bus used to transport equipment. 

Courtesy of Glenbrook North High School

Students unload equipment from the bus to set up the experiment. 

Courtesy of Glenbrook North High School

Students assemble the equipment.

Courtesy of Glenbrook North High School

Tony Valsamis sets up a camera to capture photos of the eclipse. 

Courtesy of Glenbrook North High School

A photo of the eclipse captured by Tony Valsamis. 

Courtesy of Glenbrook North High School

Mark Adams, QuarkNet’s cosmic ray studies coordinator, and student Clarissa Carr monitor data collection. 

Courtesy of Glenbrook North High School Previous Next

Immediately after arriving at Jefferson College, which would serve as home base for the research team, the students hurried about unloading equipment, setting up detectors on their mounts and connecting wires. Setup took a whole day and then some, partially because of a faulty detector.

“When one of our detectors had a faulty power cable, we all had to gather around the detector and take it apart,” says Carr, who was responsible for log-keeping during the experiment as well as setup. “We managed to put it back together and get it working—it was memorable but stressful!”

After setup, the detectors could begin collecting baseline data to be compared with data from the eclipse. The researchers had nothing left to do but wait for totality. To pass the time, students visited a local farmer’s market, played volleyball and theorized about what the eclipse might be like.

“We were all hypothesizing about what we would see during the eclipse,” says Jacob Rosenberg, a Glenbrook North student. “None of us had a clue what to expect, but we were all excited.”

The big moment  

When the day of the eclipse finally arrived, crowds of people joined the research team at Jefferson College, eager to experience the United States’ first total solar eclipse in decades. As excitement filled the air, the research team made last minute adjustments to their detectors, making sure everything would be in working order during the short window of totality. With detectors pointed at the sky and eclipse glasses at the ready, the team was prepared. 

In the minutes leading up to totality, spectators at Jefferson College peered up through their glasses, waiting until the moon completely covered the sun. 

“The total solar eclipse was incredible to look at,” Rosenberg recalls. “There was a 360-degree sunset, and we could hear the noises of nature change as people ‘ooh'ed and ‘ahh'ed.”

 Valsamis came equipped to capture photos of the eclipse, amassing over 700 pictures. 

“None of my photos mimic the experience or explain how beautiful it was,” Valsamis says. “It was like the best picture but better, and being surrounded by enthusiastic people was infectious.”

The aftermath 

In the months since it happened, the eclipse may have become a passing memory to most, but it’s stayed at the forefront of the research team’s mind. Students from Ida Crown and Glenbrook North meet at least once a month to collaborate on data analysis.

“Students had a unique opportunity to do this research almost on their own," Valsamis says. “It was incredible to see the students learn to collaborate.”

While not all the data has been analyzed yet—and some potentially interesting data points have required more intense analysis—students have already benefited from the experience of conducting research.

“I’ve learned from this experiment the importance of being knowledgeable about what you’re doing, but being open to learning more,” Carr says. “I’ve also learned a lot about teamwork and community-building.”

In 2018, Carr and Rosenberg will present some of the results from the solar eclipse study at the annual American Association of Physics Teachers conference. Both students are excited about the opportunity—although understandably a little nervous.

“It’s a little intimidating to present in front of so many smart people, but I’m not too worried," Rosenberg says. “I remind myself that anyone, no matter age or experience, can always contribute to research and learning more about the universe.”

Physics books of 2017

Tue, 12/12/2017 - 20:52

Gravitational waves take the top spot in Symmetry writer Mike Perricone’s yearly round-up of popular science books related to physics and astrophysics.

In 2017, we were treated to books about gravitational waves; unsung women critical to modern astronomy; the neutrino detector at the South Pole; and astrophysics both fast and slow.

Ripples in Spacetime: Einstein, Gravitational Waves, and the Future of Astronomy, by Govert Schilling

Einstein’s final prediction took the longest to confirm: Gravitational waves were finally detected in September of 2015, a century after the publication of his paper on general relativity. The discovery brought with it the 2017 Nobel Prize in Physics, shared by Rainer Weiss, Barry Barish and Kip Thorne. Govert Schilling, a science writer based in the Netherlands, places the discovery in the historical context of a 40-year search. Schilling is a captivating story-teller who creates a one-on-one conversation with his readers.

The Glass Universe: How the Ladies of the Harvard Observatory Took the Measure of the Stars, by Dava Sobel 

Dava Sobel (Longitude, The Planets, Galileo’s Daughter) shines a light on the irreplaceable contributions of the women “computers” at the Harvard Observatory. In the late 19th and early 20th centuries, these women exhaustively cataloged millions of stars from glass photographic plates (hence, The Glass Universe). One of them, Henrietta Swan Leavitt, concluded that the brightest variable stars had the longest periods, establishing a measuring standard across space still used today.

Astrophysics for People in a Hurry, by Neil deGrasse Tyson

As soon as it was published, Astrophysics for People in a Hurry hit No. 1 on the New York Times best-seller list. In a TV interview, author Neil deGrasse Tyson characterized the reception as “an affirmation that people are interested in science.” Learn the laws of the universe with an attitude: As Tyson says, “Yes, Einstein was a badass.”

Universal: A Guide to the Cosmos, by Brian Cox and Jeff Forshaw

Cosmology and astrophysics for those who are not in a hurry—and who enjoy a challenge. This beautiful book excels on three levels: the striking graphics, the accessible introductions escalating into detailed discussions, and the accompanying case studies exhibiting the scientific method (such as “What is Light?”). Co-authors Brian Cox and Jeff Forshaw (Why Does E=mc2?) are physics professors at the University of Manchester; Cox is also Royal Society Professor for Public Engagement in Science.

A Big Bang in a Little Room: The Quest to Create New Universes, by Zeeya Merali

Creating a new universe at a particle accelerator might sound like science fiction, or just plain preposterous—until author Zeeya Merali places the idea in the context of other feats of modern cosmology. With a PhD in theoretical physics and cosmology from Brown University, Merali takes on the topic with knowledge and humor in conversation with leaders at the intersection of cosmology and particle physics.

Three titles from the invaluable Oxford University Press A Very Short Introduction series:

Gravity: A Very Short Introduction, by Timothy Clifton

Timothy Clifton, a gravitational specialist at Queen Mary University of London, starts with the everyday experiences of gravity and advances to its effects on the universe and scientists’ efforts to link it with quantum mechanics. He also discusses the impact of the discovery of gravitational waves.

Telescopes: A Very Short Introduction, by Geoffrey Cottrell

Geoffrey Cottrell, an astrophysicist at Oxford University, explores the principles, history and major discoveries of different types of telescopes: simple optical, radio, X-ray, gamma ray and space-based. He also looks to the next generation of telescopes, such as the ALMA radio telescope array in the Atacama desert of Chile.

The Jazz of Physics: The Secret Link Between Music and the Structure of the Universe, by Stephon Alexander

Pythagoras, Kepler, Newton and Einstein all pondered the link between music and physics. The great saxophonist John Coltrane incorporated physics and geometry into his work. “In our attempts to reveal new vistas in our understanding, we often must embrace an irrational, illogical process, sometimes fraught with mistakes and improvisational thinking,” writes physicist and jazz saxophonist Stephon Alexander.

The Telescope in the Ice: Inventing a New Astronomy at the South Pole, by Mark Bowen 

Tracking a unique particle takes a unique particle detector. Meet IceCube: a cubic kilometer of “diamond-clear” ice more than a mile below the surface at the South Pole. The world’s largest particle detector, IceCube recorded the first extra-terrestrial high-energy neutrinos in 2010. Mark Bowen (Censoring Science, Thin Ice) narrates the story of the people and science behind the pursuit of the inscrutable particle. Bowen, a “recovering physicist,” journeyed to the Amundsen South Pole research station as a part of his research for the book.

Magnitude: The Scale of the Universe, by Megan Watzke and Kimberly Arcand

How big is big? How small is small? Kimberly Arcand and Megan Watzky, colleagues at NASA’s Chandra X-Ray Observatory, take an illustrated journey from subatomic particles to the most massive galaxies in the universe, from the speed of grass growing to the speed of light. They explore mass, time and temperature; speed and acceleration; and energy, pressure and sound. Watzke and Arcand’s other collaborations include Light: The Visible Spectrum and Beyond and Coloring the Universe: An Insider’s Look at Making Spectacular Images of Space.

Mass : The Quest to Understand Matter From Greek Atoms to Quantum Fields, by Jim Baggott

Even in the aftermath of uncovering the Higgs particle in 2012, Jim Baggott (The Quantum Story: A History in 40 Moments, others) points to our incomplete understanding of matter. The foundations of the universe, he says, are “built of ghosts and phantoms of a peculiar quantum kind.” Each chapter concludes with “Five things we learned,” such as Einstein’s dictum, via John A. Wheeler: “Matter tells space-time how to curve; space-time tells matter how to move.” Mass is worth some extra effort to keep up.

The Quantum Labyrinth: How Richard Feynman and John Wheeler Revolutionized Time and Reality, by Paul Halpern

Bongo-playing Richard Feynman and buttoned-down John A. Wheeler began their unlikely connection in 1939 when Feynman was Wheeler’s teaching assistant at Princeton. Wheeler’s ideas about the universe read almost like science fiction: black holes, worm holes and portals to the future and the past. Feynman won the Nobel Prize for his work in quantum electrodynamics. He depicted quantum reality as a function of alternative possibilities. Paul Halpern (Einstein’s Dice and Schrödinger’s Cat, Edge of the Universe) shows how these two formed their own alternate reality.

The PhD pioneers

Thu, 12/07/2017 - 17:29

Wenzhao Wei and Dan Rederth are the first to earn physics PhDs within the state of South Dakota.

Completing a PhD in physics is hard. It’s even harder when you’re one of the first to do it not just at your university, but at any university in your entire state.

That’s exactly the situation Wenzhao Wei and Dan Rederth found themselves in earlier this year, when completing their doctorates at the University of South Dakota and the South Dakota School of Mines and Technology, respectively. Wei and Rederth are graduates of a joint program between the two institutions. 

Wei found out just a few weeks before going in front of a committee at USD to defend her thesis. A couple of students ahead of her had dropped out of the PhD program, leaving her suddenly at the head of the pack.

“When I found out, I was very nervous,” Wei says. “When you’re the first, you don’t have any examples to follow, you don’t know how to prepare your defense, and you can’t get experience from other people who have already done it.”

She recalls running between as many professors and committee members as she could for advice. “I did a lot of checking with them and asking questions. I had no idea what they would be expecting from the first PhD student.”

Despite her wariness, and with some significant publications in the field as the first author, Dr. Wei’s defense was successful, and she is now working as a postdoc at the University of South Dakota.

Rederth knew he was the first at SDSMT but wasn’t aware it was a first in South Dakota until after he had handed in his dissertation and completed his defense. “The president of the school told me I was the first in South Dakota after I finished,” he says. “But I wasn’t aware that Wenzhao had also completed her PhD at the same time.

“Being the first, I was not prepared for the level of questioning I received during my defense – it went much deeper into physics than just my research. Together with Wenzhao, being the first in South Dakota really is a feather in the cap to something which took years of hard work to achieve.”

Dan Rederth Different paths to physics

Rederth started on his path to physics research at a young age. “The most satisfying aspect of my PhD research dates back to my childhood,” he says. “I was always intrigued by magnetism and the mystery of how it works, so it was fascinating to do my research.”

His work involved studying strange magnetic quantum effects that arise when certain particles are confined in special materials. A computer program he developed to model the effects could help bring new technologies into electronics.

For Wei’s success, you might expect she had also always made a beeline to research, but physics was actually a late calling for her. At Central China Normal University, she had studied computer science and only switched to physics at master’s level.

“In high school, I remember liking physics, but I ended up choosing computer science,” Wei says. “Then at college, I had some friends who did physics who were part of the same clubs as me, and they kept talking about really interesting things. I found I was becoming less interested in computer science and more interested in physics, so I switched.”

Wei’s thesis, entitled “Advanced germanium detectors for rare event physics searches,” and her current research involve developing technologies for new kinds of particle physics detectors—ones that use germanium, a metal-like element similar to tin and silicon. Such detectors could be used for future neutrino and dark matter experiments.

South Dakota is already home to a growing suite of physics experiments located a mile beneath the surface in the Sanford Underground Research Facility. It was in part a result of these experiments being located in the same state that Wei’s pioneering PhD program came about. USD has been involved with several experiments at SURF, among them the Deep Underground Neutrino Experiment, which will study neutrinos in a beam sent from Fermilab 1300 kilometers away.

“DUNE and SURF have been a vehicle to move the physics PhD program at USD forward,” says Dongming Mei, Wei’s doctoral advisor at USD. “With the progress of DUNE, future PhD students from USD will be exposed to thousands of world-class scientists and engineers.”

Post-doctorate, Wei is now continuing the research she began during her thesis. But with a twist.

“For my PhD, I did lots of computer simulations of dark matter interactions, so I spent a lot of time stuck at a computer,” Wei says. “Now I’m actually able to get hands-on with the  germanium crystals we grow here at USD and test them for things like their electrical properties.”

So where next for South Dakota’s first locally certified doctors of physics?

“I want to stay in physics for the long-term,” Wei says. “I taught some physics to undergraduates during my PhD and really loved it, so I’m hoping to be a researcher and lecturer one day.”

Rederth, too, wants to help inspire the next generation. “I want to stay in the Black Hills area to help raise science and math proficiency in the local schools. I’ve been a judge for the local science fair and would like to become more involved,” he says.

Perhaps some of their future students will go on to join the list of South Dakota’s physics doctorates, started by their trailblazing teachers.

Radio lab

Tue, 12/05/2017 - 17:01

Have a question for Fermilab? Tune in to a Fermilab frequency over the next two weeks.

Calling all amateur radio operators: Fermilab employees are taking to the air waves.

From December 2-17, the Fermilab Amateur Radio Club, whose membership includes laboratory employees, former employees and guests, is commemorating the lab’s 50th birthday with two weeks of ham radio activity. Tune in at the right frequency at the right time, and you could communicate directly with a member of the Fermilab community to ask your burning questions. How does an accelerator bring particles to near light speed? When did the universe begin? How did Fermilab begin?

You just might hear a friendly voice—or receive a Morse code message—at the other end.

The club has established a call sign for this special two-week event: W9F. They will operate daily on all frequencies and modes—voice, Morse code and others. The anticipated frequencies of operation are 14.260, 14.340, 7.250 and 7.275 MHz. There may also be operations on 7.040, 10.130 and 14.040.

“Amateur radio is the original electronic social media,” says Fermilab engineering physicist Kermit Carlson. “It’s practiced as an avocation without pay or pecuniary interest by people worldwide.”

According to ARRL, the national association for amateur radio, there are more than 800,000 amateur radio operators in the United States and roughly 2 million worldwide—in virtually every country.

“Amateur radio is the original electronic social media.”

“Ham radio is a hobby practiced by everyone from school kids to doctors,” Carlson says. “It’s a wide cross section of society.”

The Fermilab club has no radio station, so the approximately 10 on-air hosts will use their personal home stations to establish radio contacts. Harry Przekop, a retired medical physicist who conducted his graduate studies at Fermilab, came up with the idea for the event, and he will be one of the on-air hosts.

It’s a fitting way to celebrate a laboratory known for its forefront science. The world’s amateur radio operators tend to be technologically astute folks, club members say. And the wonder of channeling nature is often what draws people to using amateur radio.

“I remember when I was a little kid sitting in the dark in my grandparents’ living room listening to the BBC,” says Fermilab engineer David Peterson. “How could these signals come from thousands of miles away and get picked up on a little piece of wire in the tree outside my grandparents’ living room and come out the speaker of my radio?”

The technical side of operating amateur radio dovetailed with Peterson’s career fairly well.

“Electromagnetic fields — it’s all kind of the same technology,” Peterson says.

Once the two-week, on-air celebration is over, the hosts will make available a commemorative QSL card, requests for which can be sent to ARRL via email

So tune in, say hi, and be a part of Fermilab’s 50th-anniversary on-air celebration. Talk to an on-air expert to learn what Fermilab does and the discoveries it’s made. Do it from the comfort of your ham radio setup. And maybe collect a QSL card for your collection.

A winning map

Mon, 12/04/2017 - 03:16

The Fundamental Physics Prize recognizes WMAP’s contributions to precision cosmology.

The sixth annual Breakthrough Prize in Fundamental Physics has been awarded to an experiment that revolutionized cosmology and mapped the history of our universe. The $3 million prize was given to the science team and five leaders who worked on the Wilkinson Microwave Anisotropy Probe, which investigated matter, the Big Bang and the early conditions of our universe.

 “WMAP surveyed the patterns of the oldest light, and we used the laws of physics to deduce from these patterns answers to our questions,” said Chuck Bennett, the principal investigator of WMAP. He received the award along with Gary Hinshaw, Norman Jarosik, Lyman Page and David Spergel. “Science has let us extend our knowledge of the universe to far beyond our physical reach.”

The Breakthrough Prizes, which are also awarded in life sciences and mathematics, celebrate both the science itself and the work done by scientists. The award was founded by Sergey Brin, Anne Wojcicki, Jack Ma, Cathy Zhang, Yuri and Julia Milner, Mark Zuckerberg and Priscilla Chan with the goal of inspiring more people to pursue scientific endeavors.

WMAP, a joint NASA and Princeton University project that ran from 2001 to 2010, has many claims to fame. Scientists have used the spacecraft’s data to determine the age of the universe (13.77 billion years old) and pinpoint when stars first began to shine (about 400 million years after the Big Bang). WMAP results also revealed the density of matter and the surprising makeup of our universe: roughly 71 percent dark energy, 25 percent dark matter and 4 percent visible matter.

From its home one million miles from Earth, WMAP precisely measured a form of light left over from the Big Bang: the cosmic microwave background (CMB). Researchers assembled this data into a “baby picture” of our universe when it was a mere 375,000 years old. WMAP observations support the theory of inflation—that a rapid period of expansion just after the Big Bang led to fluctuations in the distribution of matter, eventually leading to the formation of galaxies.

Scientists still hope to unlock more secrets of the universe using the CMB, and various experiments, such as BICEP3 and the South Pole Telescope, are already running to address these cosmological questions. One thing scientists would love to find? A twist on a hot topic: primordial gravitational waves left over from the Big Bang.

“There is still much we do not understand, such as the first moments of the universe,” Bennett said. “So there will be new breakthroughs in the future.”

NASA/WMAP Science Team

LHC data: how it’s made

Tue, 11/28/2017 - 18:47

In the Large Hadron Collider, protons become new particles, which become energy and light, which become data.

Scientists have never actually seen the Higgs boson. They’ve never seen the inside of a proton, either, and they’ll almost certainly never see dark matter. Many of the fundamental patterns woven into the fabric of nature are completely imperceptible to our clunky human senses.

But scientists don’t need to see particles to learn about their properties and interactions. Physicists can study the subatomic world with particle detectors, which gather information from events that occur much faster and are much smaller than the eye can see.

But what is this information, and how exactly do detectors gather it? At experiments at the Large Hadron Collider, the world's largest and most powerful particle accelerator, it all begins with a near-light-speed race.

Starting with a bang

The LHC is built in a ring 17 miles in circumference. Scientists load bunches of protons into this ring and send them hurtling around in opposite directions, gaining more and more energy with each pass. 

By the time the LHC has boosted the proton beams to their maximum energy, they will have traveled a distance equivalent to a round-trip journey between Earth and the sun. They will be moving so fast that they no longer convert energy into speed but in effect swell with mass instead.

Once the protons are ramped up to their final energy, the LHC’s magnets nudge the two beams into a collision course at four intersections around the ring. 

“When two protons traveling at near light speeds collide head-on, the impact releases a surge of energy unimaginably quickly in an unimaginably small volume of space,” says Dhiman Chakraborty, a professor of Physics at Northern Illinois University working on the ATLAS experiment. “In that miniscule volume, conditions are similar to those that prevailed when the universe was a mere tenth of a nanosecond old.”

This energy is often converted directly into mass according to Einstein’s famous equation, E=mc2, resulting in birth of exotic particles not to be found anywhere else on Earth. These particles, which can include Higgs bosons, are extremely short-lived.

“They decay instantaneously and spontaneously into less massive, more stable ‘daughter’ particles,” Chakraborty says. “The large mass of the exotic parent particle, being converted back into energy, sends its much lighter daughters flying off at near light speeds.”

Even though these rare particles are short-lived, they give scientists a peek at the texture of spacetime and the ubiquitous fields woven into it. 

“So much so that the existence of the entire universe we see today—ourselves as observers included—is owed to [the particles and fields we cannot see],” he says.

This CMS experiment event display identifies an electron and a muon passing through the detector.

Courtesy of CMS Collaboration Enter the detector

All of this happens in less than a millionth of a trillionth of a second. Even though the LHC’s detectors encompass the beampipe and are only a few centimeters away from the collison, it is impossible for them to see the new heavy particles, which often disintegrate before they can move a distance equal to the diameter of an atomic nucleus.

But the detectors can “see” the byproducts of their decay. The Higgs bosons can transform into pairs of photons, for example. When those photons hit the atoms and molecules that make up the detector material, they radiate sparkles of light and jolts of energy like meteorites blazing through the atmosphere. Sensors inhale these dim twinkles and transform them into electrical signals, recording where and when they arrived. 

“Each pulse is a snapshot of space and time,” Chakraborty says. “They tell us exactly where, when and how fast those daughter particles traversed our detector.”

A single proton-proton collision can generate several high-energy daughter particles, some of which produce showers of hundreds more. These streams of particles release detectable energy as they hit the detectors and generate electrical pulses. The time, location, length, shape, height and total energy of each electrical pulse are directly translated into data bits by an electronic readout card.

Much the way biologists chart animal tracks to study the speed, direction and size of a herd, physicists study the shape of these electrical pulses to characterize the passing particles. A long, broad electrical pulse indicates that a large stream of particles grazed across the detector, but a pulse with a sharp peak suggests that a small pack cut straight through.

These electrical pulses create a multifaceted connect-the-dots. Algorithms quickly identify patterns in the cascade of hits and rapidly reconstruct particle energies and tracks.

“We only have a few microseconds to reconstruct what happened before the next batch of collisions arrives,” says Tulika Bose, an associate professor at Boston University working on the CMS experiment. “We can’t keep all the data, so we use automated systems to crudely reconstruct particles like muons and electrons. 

“If the event looks interesting enough based on this limited amount of information, we keep all the data from that snapshot in time and save them for further analysis.”

These interesting events are packaged and dispatched upstairs to a second series of automated gatekeepers that further evaluate the quality and characteristics of these collision snapshots. Preprogrammed algorithms identify more particles in the snapshot. This entire process takes less than a millisecond, faster than the blink of a human eye.

Even then, humans won’t lay eyes on the data until after it undergoes a strenuous suite of processing and preparation for analysis.

Humans can’t see the Higgs boson, but by tracing its byproducts back to a single Higgs-like origin, they were able to gather enough evidence to discover it.

“In the five years since that discovery, we’ve produced hundreds of thousands more Higgs bosons and reconstructed a good number of them,” Chakraborty says. “They’re being studied intensely with the goal of gaining insight into deeper mysteries of nature.”

A win for physics and geology

Wed, 11/22/2017 - 18:23

For the first time, scientists have measured the rate at which high-energy neutrinos are absorbed by our planet, a development that could lead to discoveries about physics and the Earth.

When describing neutrinos to the public, scientists often share an astounding fact: About 100 trillion of them pass through your body every second. Neutrinos are extremely abundant in the universe, and they only rarely interact with other matter. That’s why they’re constantly streaming through you—and our entire planet.

But every once and a while, a neutrino hits something.

A new result from the IceCube experiment, published today in Nature, provides a unique measurement of how often that happens. Future improvements on the result could lead to discoveries about neutrinos, particle physics or even the Earth’s inaccessible core.

Colliding with matter can cause a neutrino to shed some or all of its energy. When a neutrino loses all of its energy, it is destroyed, converted into a shower of other particles. It’s a small but “very nasty explosion of stuff,” says scientist Sandra Miarecki, who led the recently published study as a student at UC Berkeley and who now works as a professor at the US Air Force Academy in Colorado.

The more energy a neutrino has, and the denser the matter through which it is traveling, the more likely this is to happen. When neutrinos reach energies of millions of billions of electronvolts, they should find it almost impossible to make it all the way through our planet.

That had been the prediction, at least. But until the IceCube experiment, no one had ever actually measured it.

IceCube is an array of 5160 basketball-sized light sensors sunk into a cubic kilometer of Antarctic ice. When a neutrino smacks into a nucleus in the Earth, it converts its energy into another particle, a muon, which creates a flash of blue light as it passes through the ice. IceCube’s sensors record the trail of that light, letting scientists know how much energy the neutrino had and what direction it came from. Measuring the direction tells scientists how much of the Earth the neutrino has traveled through to get there.

For her thesis, Miarecki used data from IceCube’s 2010-2011 year of operation (the year prior to the completion of the detector) to measure what’s called the neutrino cross-section, the likelihood that a neutrino would interact with a nucleus, depending on the neutrino's energy.

“The thing that’s really interesting about this measurement is that we’re using neutrinos with energies tens to hundreds of times higher than what’s available at accelerators like the Large Hadron Collider,” says Spencer Klein of Lawrence Berkeley National Laboratory and UC Berkeley, Miarecki’s thesis advisor. “IceCube is the first experiment that’s big enough to do anything like this.”

This first measurement of the neutrino cross-section at high energies matched scientists’ predictions based on the Standard Model of particle physics. In this dataset, no million-billion-electronvolt neutrinos made it through from the opposite side of the Earth.

The concept of seemingly unstoppable neutrinos finally meeting their match “actually shook me a little,” when he first joined the experiment, says IceCube Spokesperson Darren Grant of the University of Alberta. “I’d been working on neutrinos for, oh goodness, 10 years, but they’d always been at low energies.”

But with more data—and IceCube has collected almost seven more years’ worth since this study began—that measurement will grow more precise. There is still a chance it will reveal a discrepancy, which could point to a new discovery in physics. “It’s just going to take someone to do the work,” Miarecki says.

Knowing the neutrino cross-section with great accuracy could also help out another field: geology.

“It’s one of the few ways I am aware of where you could actually refine the deep interior picture of the Earth to some higher precision than we know it today,” Grant says.

Scientists’ current best measurements of the interior of the Earth come from sensors measuring how vibrations move through the planet during earthquakes. These measurements are highly accurate, and over the last couple of decades, no one has found a way to improve them.

But if scientists can combine their knowledge of neutrinos with their knowledge of the center of the Earth, they should be able to make very accurate predictions about how many neutrinos they will see coming through different sections of the ground. If their measurements disagree with those predictions, it could be a sign that there’s something going on inside the Earth that they don’t yet understand.