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dimensions of particle physics
Updated: 1 hour 29 min ago

Scientists make rare achievement in study of antimatter

Thu, 10/19/2017 - 18:40

Through hard work, ingenuity and a little cooperation from nature, scientists on the BASE experiment vastly improved their measurement of a property of protons and antiprotons.

Scientists at CERN are celebrating a recent, rare achievement in precision physics: Collaborators on the BASE experiment measured a property of antimatter 350 times as precisely as it had ever been measured before.

The BASE experiment looks for undiscovered differences between protons and their antimatter counterparts, antiprotons. The result, published in the journal Nature, uncovered no such difference, but BASE scientists say they are hopeful the leap in the effectiveness of their measurement has potentially brought them closer to a discovery.

“According to our understanding of the Standard Model [of particle physics], the Big Bang should have created exactly the same amount of matter and antimatter, but [for the most part] only matter remains,” says BASE Spokesperson Stefan Ulmer. This is strange because when matter and antimatter meet, they annihilate one another. Scientists want to know how matter came to dominate our universe.

“One strategy to try to get hints to understand the mechanisms behind this matter-antimatter symmetry is to compare the fundamental properties of matter and antimatter particles with ultra-high precision,” Ulmer says.

Scientists on the BASE experiment study a property called the magnetic moment. The magnetic moment is an intrinsic value of particles such as protons and antiprotons that determines how they will orient in a magnetic field, like a compass. Protons and antiprotons should behave exactly the same, other than their charge and direction of orientation; any differences in how they respond to the laws of physics could help explain why our universe is made mostly of matter.

This is a challenging measurement to make with a proton. Measuring the magnetic moment of an antiproton is an even bigger task. To prevent antiprotons from coming into contact with matter and annihilating, scientists need to house them in special electromagnetic traps.

While antiprotons generally last less than a second, the ones used in this study were placed in a unique reservoir trap in 2015 and used one by one, as needed, for experiments. The trapped antimatter survived for more than 400 days.

During the last year, Ulmer and his team worked to improve the precision of the most sophisticated technqiues developed for this measurement in the last decade.

They did this by improving thier cooling methods. Antiprotons at temperatures close to absolute zero move less than room-temperature ones, making them easier to measure.

Previously, BASE scientists had cooled each individual antiproton before measuring it and moving on to the next. With the improved trap, the antiprotons stayed cool long enough for the scientists to swap an antiproton for a new one as soon as it became too hot.

“Developing an instrument stable enough to keep the antiproton close to absolute zero for 4-5 days was the major goal,” says Christian Smorra, the first author of the study.

This allowed them to collect data more rapidly than ever before. Combining this instrument with a new technique that measures two particles simultaneously allowed them to break their own record from last year’s measurement by a longshot.

“This is very rare in precision physics, where experimental efforts report on factors of greater than 100 magnitude in improvement,” Ulmer says.

The results confirm that the two particles behave exactly the same, as the laws of physics would predict. So the mystery of the imbalance between matter and antimatter remains.

Ulmer says that the group will continue to improve the precision of their work. He says that, in five to 10 years, they should be able to make a measurement at least twice as precise as this latest one. It could be within this range that they will be able to detect subtle differences between protons and antiprotons.

“Antimatter is a very unique probe,” Ulmer says. “It kind of watches the universe through very different glasses than any matter experiments. With antimatter research, we may be the only ones to uncover physics treasures that would help explain why we don’t have antimatter anymore.”

Scientists observe first verified neutron-star collision

Mon, 10/16/2017 - 16:06

For the first time, experiments have seen both light and gravitational waves released by a single celestial crash.

Today scientists announced the first verified observation of a neutron star collision. LIGO detected gravitational waves radiating from two neutron stars as they circled and merged, triggering 50 additional observational groups to jump into action and find the glimmer of this ancient explosion.

This observation represents the first time experiments have seen both light and gravitational waves from a single celestial crash, unlocking a new era of multi-messenger astronomy.

On August 17 at 7:41 a.m. Eastern Time, NASA astronomer Julie McEnery had just returned from an early morning row on the Anacostia River when her experiment, the Fermi Gamma Ray Space Telescope, sent out an automatic alert that it had just recorded a burst of gamma rays coming from the southern constellation Hydra. By itself, this wasn’t novel; the Gamma-ray Burst Monitor instrument on Fermi has seen approximately 2 gamma-ray outbursts per day since its launch in 2008. 

“Forty minutes later, I got an email from a colleague at LIGO saying that our trigger has a friend and that we should buckle up,” McEnery says.

Most astronomy experiments, including the Fermi Gamma Ray Space Telescope, watch for light or other particles emanating from distant stars and galaxies. The LIGO experiment, on the other hand, listens for gravitational waves. Gravitational waves are the equivalent of cosmic tremors, but instead of rippling through layers of rock and dirt, they stretch and compress space-time itself.

Exactly 1.7 seconds before Fermi noticed the gamma ray burst, a set of extremely loud gravitational waves had shaken LIGO’s dual detectors.

“The sky positions overlapped, strongly suggesting the two signals were coming from the same astronomical event,” says Daniel Holz, a professor at the University of Chicago and member of LIGO collaboration and the Dark Energy Survey Gravitational Wave group.

LIGO reconstructed the location and distance of the event and sent an alert to their allied astronomers. About 12 hours later, right after sunset, multiple astronomical surveys found a glowing blue dot just above the horizon in the area LIGO predicted.

“It lasted for two weeks, and we observed it for about an hour every night,” says Jim Annis, a researcher at the US Department of Energy’s Fermi National Accelerator Laboratory, the lead institution on the Dark Energy Survey. “We used telescopes that could see everything from low-energy radio waves all the way to high-energy X-rays, giving us a detailed image of what happened immediately after the initial collision.”

Neutron stars are roughly the size of the island of Nantucket but have more mass than the sun. They have such a strong gravitational pull that all their matter has been squeezed and transformed into a single, giant atomic nucleus consisting entirely of neutrons.

“Right before two neutron stars collide, they circle each other about 100 times a second,” Annis says. “As they collide, huge electromagnetic tornados erupt at the poles and material is sprayed out in all directions at close to the speed of light.”

As they merge, neutron stars release a quick burst of gamma radiation and then a spray of decompressing neutron star matter. Exotic heavy elements form and decay, dumping enough energy that the surface reaches temperatures of 20,000 degrees Kelvin. That's almost four times hotter than the surface of the sun and much brighter. Scientists theorize that a good portion of the heavy elements in our universe, such as gold, originated in neutron star collisions and other massively energetic events.

Since coming online in September 2015, the US-based LIGO collaboration and their Italy-based partners, the Virgo collaboration, have reported detecting five bursts of gravitational waves. Up until now, each of these observations has come from a collision of black holes.

“When two black holes collide, they emit gravitational waves but no light,” Holz says. “But this event released an enormous amount of light and numerous astronomical surveys saw it. Hearing and seeing the event provides a goldmine of information, and we will be mining the data for years to come.”

This is a Rosetta Stone-type discovery, Holz says. “We’ve learned about the processes that neutron stars are undergoing as they fling out matter and how this matter synthesizes into some of the elements we find on Earth, such as gold and platinum,” he says. “In addition to teaching us about mysterious gamma-ray bursts, we can use this event to calculate the expansion rate of the universe. We will be able to estimate the age and composition of the universe in an entirely new way.”

For McEnery, the discovery ushers in a new age of cooperation between gravitational-wave experiments and experiments like her own.

“The light and gravitational waves from this collision raced each other across the cosmos for 130 million years and hit earth 1.7 seconds apart,” she says. “This shows that both are moving at the speed of light, as predicted by Einstein. This is what we’ve been hoping to see.”

Xenon takes a turn in the LHC

Thu, 10/12/2017 - 23:21

For the first time, the Large Hadron Collider is accelerating xenon nuclei for experiments.

Most of the year, the Large Hadron Collider at CERN collides protons. LHC scientists have also accelerated lead nuclei stripped of their electrons. Today, for just about eight hours, they are experimenting with a different kind of nucleus: xenon.

Xenon is a heavy noble gas that exists in trace quantities in the air. Xenon nuclei are about 40 percent lighter than lead nuclei, so xenon-xenon collisions have a different geometry and energy distribution than lead-lead collisions.

“When two high-energy nuclei collide, they can momentarily form a droplet of quark gluon plasma, the primordial matter that filled our universe just after the big bang,” says Peter Steinberg, a physicist at the US Department of Energy’s Brookhaven National Laboratory and a heavy-ion coordinator for the ATLAS experiment at CERN. “The shape of the colliding nuclei influences the initial shape of this droplet, which in turn influences how the plasma flows and finally shows up in the angles of the particles we measure. We’re hoping that these smaller droplets from xenon-xenon collisions give us deeper insight into how this still-mysterious process works at truly subatomic length scales.”

Not all particles that travel through CERN’s long chain of interconnected accelerators wind up in the LHC. Earlier this year, scientists were loading xenon ions into the accelerator and firing them at a fixed-target experiment instead.

“We can have particles from two different sources feeding into CERN’s accelerator complex,” says Michaela Schaumann, a physicist in LHC operation working on the heavy-ion program. “The LHC’s injectors are so flexible that, once everything is set up properly, they can alternate between accelerating protons and accelerating ions a few times a minute.”

Having the xenon beam already available provided an opportunity to send xenon into the LHC for first (and potentially only) time. It took some serious additional work to bring the beam quality up to collider levels, Schaumann says, but today it was ready to go. 

“We are keeping the intensities very low in order to fulfil machine protection requirements and be able to use the same accelerator configuration we apply during the proton-proton runs with xenon beams,” Schaumann says. “We needed to adjust the frequency of the accelerator cavities [because more massive xenon ions circulate more slowly than protons], but many of the other machine settings stayed roughly the same.”

This novel run tests scientists’ knowledge of beam physics and shows the flexibility of the LHC. Scientists say they are hopeful it could reveal something new.

“We can learn a lot about the properties of the hot, dense matter from smaller collision systems,” Steinberg says. “They are a valuable bridge to connect what we observe in lead-lead collisions to strikingly similar observations in proton-proton interactions.”

A play in parallel universes

Tue, 10/10/2017 - 16:17

Constellations illustrates the many-worlds interpretation of quantum mechanics—with a love story.

The play Constellations begins with two people, Roland and Marianne, meeting for the first time. It’s a short scene, and it doesn’t go well. Then the lights go down, come back up, and it’s as if the scene has reset itself. The characters meet for the first time, again, but with slightly different (still unfortunate) results.

The entire play progresses this way, showing multiple versions of different scenes between Roland, a beekeeper, and Marianne, an astrophysicist. 

In the script, each scene is divided from the next by an indented line. As the stage notes explain: “An indented rule indicates a change in universe.”

To scientist Richard Partridge, who recently served as a consultant for a production of Constellations at TheatreWorks Silicon Valley, it’s a play about quantum mechanics. 

“Quantum mechanics is about everything happening at once,” he says.

We don’t experience our lives this way, but atoms and particles do. 

In 1927, physicists Niels Bohr and Werner Heisenberg wrote that, on the scale of atoms and smaller, the properties of physical systems remain undefined until they are measured. Light, for example, can behave as a particle or a wave. But until someone observes it to be one or the other, it exists in a state of quantum superposition: It is both a particle and a wave at the same time. When a scientist takes a measurement, the two possibilities collapse into a single truth.

Physicist Erwin Schrodinger illustrated this with a cat. He created a thought experiment in which the decay of an atom—an event ruled by quantum mechanics—would trigger toxic gas to be released in a steel chamber with a cat inside. By the rules of quantum mechanics, until someone opened the chamber, the cat existed in a state of superposition: simultaneously alive and dead. 

Some interpretations of quantum mechanics dispute the idea that observing a system can determine its true state. In the many-worlds interpretation, every possibility exists in a giant collection of parallel realities. In some, the cat lives. In others, it does not. 

In some Constellations universes, the astrophysicist and the beekeeper fall in love. In others, they do not. “So it’s not really about physics,” Partridge says. 

Constellations director Robert Kelley, who founded TheatreWorks in 1970, agrees. He says he was intimidated by the physics concepts in the play at first but that he was eventually drawn to the relationship at its core. 

“With all of these things swirling around in the play, what really counts is the relationship between two people and the love that grows between them,” he says. “I found that a very charming message for Silicon Valley. We’re surrounded by a whole lot of technology, but probably for most people what counts is when you get home and you’re on the couch and your one-and-a-half-year-old shows up.” 

TheatreWorks in Silicon Valley production of Constellations

Cosmologist Marianne (Carie Kawa) and beekeeper Roland (Robert Gilbert) explore the ever-changing mystery of “what ifs” in the regional premiere of Constellations presented by TheatreWorks Silicon Valley, August 23-September 17, at the Mountain View Center for the Performing Arts. 

Photo by Kevin Berne

Cosmologist Marianne (Carie Kawa) and beekeeper Roland (Robert Gilbert) explore the ever-changing mystery of “what ifs” in the regional premiere of Constellations presented by TheatreWorks Silicon Valley, August 23-September 17, at the Mountain View Center for the Performing Arts. 

Photo by Kevin Berne

Cosmologist Marianne (Carie Kawa) and beekeeper Roland (Robert Gilbert) explore the ever-changing mystery of “what ifs” in the regional premiere of Constellations presented by TheatreWorks Silicon Valley, August 23-September 17, at the Mountain View Center for the Performing Arts. 

Photo by Kevin Berne

Cosmologist Marianne (Carie Kawa) and beekeeper Roland (Robert Gilbert) explore the ever-changing mystery of “what ifs” in the regional premiere of Constellations presented by TheatreWorks Silicon Valley, August 23-September 17, at the Mountain View Center for the Performing Arts. 

Photo by Kevin Berne

Cosmologist Marianne (Carie Kawa) and beekeeper Roland (Robert Gilbert) explore the ever-changing mystery of “what ifs” in the regional premiere of Constellations presented by TheatreWorks Silicon Valley, August 23-September 17, at the Mountain View Center for the Performing Arts. 

Photo by Kevin Berne

Cosmologist Marianne (Carie Kawa) and beekeeper Roland (Robert Gilbert) explore the ever-changing mystery of “what ifs” in the regional premiere of Constellations presented by TheatreWorks Silicon Valley, August 23-September 17, at the Mountain View Center for the Performing Arts. 

Photo by Kevin Berne

Cosmologist Marianne (Carie Kawa) and beekeeper Roland (Robert Gilbert) explore the ever-changing mystery of “what ifs” in the regional premiere of Constellations presented by TheatreWorks Silicon Valley, August 23-September 17, at the Mountain View Center for the Performing Arts. 

Photo by Kevin Berne Previous Next

Kelley says that he found something familiar in the many timelines of the play. “It’s really kind of fun to see all that happen because it’s common ground for us as human beings: You hang up the phone and think, ‘If only I’d said that or hadn’t said that.’ It’s a fascinating thought that every single thing that happens will then determine every single other thing that happens.”

Constantly resetting and replaying the same scenes “was very acrobatic,” says Los Angeles-based actress Carie Kawa, who played Marianne in the TheatreWorks production, which concluded in September. “And there were emotional acrobatics—just jumping into different emotional states. Usually you get a little longer arc; this play is just all middles, almost like shooting a film.”

To her, the repeats and jumps were familiar in a different way: They were an encapsulation of the experience of acting.

“We do the play over and over again,” she says. “It’s the same scene, but it’s different every single time. And if we’re doing it right, we’re not thinking about the scene that just happened or the scene that’s to come, we’re in the moment.”

The play will mean different things to different people, Kawa says. 

“A teacher once told me a story about theater and a perspective that he had,” she says. “At first he said, ‘Theater is important because everybody can come together and feel the same feeling at the same time and know that we’re all okay.’

“But as he progressed in this artistry he realized that, no, what’s happening is everybody is feeling a slightly different feeling at the same time. And that’s OK. That’s what helps us experience our humanity and the humanity of the other people around us. We’re all alone in this together.”

A radio for dark matter

Thu, 10/05/2017 - 15:23

Instead of searching for dark matter particles, a new device will search for dark matter waves.

Researchers are testing a prototype “radio” that could let them listen to the tune of mysterious dark matter particles. 

Dark matter is an invisible substance thought to be five times more prevalent in the universe than regular matter. According to theory, billions of dark matter particles pass through the Earth each second. We don’t notice them because they interact with regular matter only very weakly, through gravity.

So far, researchers have mostly been looking for dark matter particles. But with the dark matter radio, they want to look for dark matter waves.

Direct detection experiments for dark matter particles use large underground detectors. Researchers hope to see signals from dark matter particles colliding with the detector material. However, this only works if dark matter particles are heavy enough to deposit a detectable amount energy in the collision. 

“If dark matter particles were very light, we might have a better chance of detecting them as waves rather than particles,” says Peter Graham, a theoretical physicist at the Kavli Institute for Particle Astrophysics and Cosmology, a joint institute of Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory. “Our device will take the search in that direction.”

The dark matter radio makes use of a bizarre concept of quantum mechanics known as wave-particle duality: Every particle can also behave like a wave. 

Take, for example, the photon: the massless fundamental particle that carries the electromagnetic force. Streams of them make up electromagnetic radiation, or light, which we typically describe as waves—including radio waves. 

The dark matter radio will search for dark matter waves associated with two particular dark matter candidates.  It could find hidden photons—hypothetical cousins of photons with a small mass. Or it could find axions, which scientists think can be produced out of light and transform back into it in the presence of a magnetic field.

“The search for hidden photons will be completely unexplored territory,” says Saptarshi Chaudhuri, a Stanford graduate student on the project. “As for axions, the dark matter radio will close gaps in the searches of existing experiments.”

Intercepting dark matter vibes

A regular radio intercepts radio waves with an antenna and converts them into sound. What sound depends on the station. A listener chooses a station by adjusting an electric circuit, in which electricity can oscillate with a certain resonant frequency. If the circuit’s resonant frequency matches the station’s frequency, the radio is tuned in and the listener can hear the broadcast.

The dark matter radio works the same way. At its heart is an electric circuit with an adjustable resonant frequency. If the device were tuned to a frequency that matched the frequency of a dark matter particle wave, the circuit would resonate. Scientists could measure the frequency of the resonance, which would reveal the mass of the dark matter particle. 

The idea is to do a frequency sweep by slowly moving through the different frequencies, as if tuning a radio from one end of the dial to the other.

The electric signal from dark matter waves is expected to be very weak. Therefore, Graham has partnered with a team led by another KIPAC researcher, Kent Irwin. Irwin’s group is developing highly sensitive magnetometers known as superconducting quantum interference devices, or SQUIDs, which they’ll pair with extremely low-noise amplifiers to hunt for potential signals.

In its final design, the dark matter radio will search for particles in a mass range of trillionths to millionths of an electronvolt. (One electronvolt is about a billionth of the mass of a proton.) This is somewhat problematic because this range includes kilohertz to gigahertz frequencies—frequencies used for over-the-air broadcasting. 

“Shielding the radio from unwanted radiation is very important and also quite challenging,” Irwin says. “In fact, we would need a several-yards-thick layer of copper to do so. Fortunately we can achieve the same effect with a thin layer of superconducting metal.”

One advantage of the dark matter radio is that it does not need to be shielded from cosmic rays. Whereas direct detection searches for dark matter particles must operate deep underground to block out particles falling from space, the dark matter radio can operate in a university basement.

The researchers are now testing a small-scale prototype at Stanford that will scan a relatively narrow frequency range. They plan on eventually operating two independent, full-size instruments at Stanford and SLAC.

“This is exciting new science,” says Arran Phipps, a KIPAC postdoc on the project. “It’s great that we get to try out a new detection concept with a device that is relatively low-budget and low-risk.” 

The dark matter disc jockeys are taking the first steps now and plan to conduct their dark matter searches over the next few years. Stay tuned for future results.

The dark matter radio disc jockeys. Front row, from left: Carl Dawson, Hsiao-Mei “Sherry” Cho and Saptarshi Chaudhuri. Back row, from left: Arran Phipps, Stephen Kuenstner and Kent Irwin. Not pictured: Dale Li and Peter Graham.

Dawn Harmer/SLAC

The dark matter radio is placed inside a 2-millimeter-thick superconducting niobium shield. When lowered into the blue dewar and cooled by liquid helium, the shield blocks interference from outside sources, such as radio stations, but is easily penetrated by dark matter. 

Dawn Harmer/SLAC

Layers of thermal barriers (top) are used to block heat from the laboratory and keep the radio cold. A cable inside the center rod brings signals from inside the shield to the outside world.

Dawn Harmer/SLAC

Dark matter waves should oscillate at a specific frequency corresponding to the mass of the dark matter particle. A spike in power will occur if the radio is tuned to match that frequency.

Dawn Harmer/SLAC

It takes about one day to cool the probe from room temperature to the operating temperature of negative 450 degrees Fahrenheit.

Dawn Harmer/SLAC Previous Next

Nobel recognizes gravitational wave discovery

Tue, 10/03/2017 - 12:42

Scientists Rainer Weiss, Kip Thorne and Barry Barish won the 2017 Nobel Prize in Physics for their roles creating the LIGO experiment.

After being passed up for the honor last year, three scientists who made essential contributions to the LIGO collaboration have been awarded the 2017 Nobel Prize in Physics.

Rainer Weiss will share the prize with Kip Thorne and Barry Barish for their roles in the discovery of gravitational waves, ripples in space-time predicted by Albert Einstein. Weiss and Thorne conceived of the experiment, and project manager Barish is credited with reviving the struggling experiment and making it happen.

“I view this more as a thing that recognizes the work of about 1000 people,” Weiss said during a Q&A after the announcement this morning. “It’s really a dedicated effort that has been going on, I hate to tell you, for as long as 40 years, people trying to make a detection in the early days and then slowly but surely getting the technology together to do it.”

A third founder of LIGO, scientist Ronald Drever, died in March. Nobel Prizes are not awarded posthumously.

According to Einstein’s general theory of relativity, powerful cosmic events release energy in the form of waves traveling through the fabric of existence at the speed of light. LIGO detects these disturbances when they disrupt the symmetry between the passages of identical laser beams traveling identical distances.

The setup for the LIGO experiment looks like a giant L, with each side stretching about 2.5 miles long. Scientists split a laser beam and shine the two halves down the two sides of the L. When each half of the beam reaches the end, it reflects off a mirror and heads back to the place where its journey began.

Normally, the two halves of the beam return at the same time. When there’s a mismatch, scientists know something is going on. Gravitational waves compress space-time in one direction and stretch it in another, giving one half of the beam a shortcut and sending the other on a longer trip. LIGO is sensitive enough to notice a difference between the arms as small as 1000th the diameter of an atomic nucleus.

Scientists on LIGO and their partner collaboration, called Virgo, reported the first detection of gravitational waves in February 2016. The waves were generated in the collision of two black holes with 29 and 36 times the mass of the sun 1.3 billion years ago. They reached the LIGO experiment as scientists were conducting an engineering test.

“It took us a long time, something like two months, to convince ourselves that we had seen something from outside that was truly a gravitational wave,” Weiss said.

LIGO, which stands for Laser Interferometer Gravitational-Wave Observatory, consists of two of these pieces of equipment, one located in Louisiana and another in Washington state. The experiment is operated jointly by MIT, Weiss’s home institution, and Caltech, home institution for Barish and Thorne. The experiment has collaborators from more than 80 institutions from more than 20 countries. A third interferometer, operated by Virgo, recently joined LIGO to make the first joint observation of gravitational waves.

Conjuring ghost trains for safety

Thu, 09/28/2017 - 19:33

A Fermilab technical specialist recently invented a device that could help alert oncoming trains to large vehicles stuck on the tracks.

Browsing YouTube late at night, Fermilab Technical Specialist Derek Plant stumbled on a series of videos that all begin the same way: a large vehicle—a bus, semi or other low-clearance vehicle—is stuck on a railroad crossing. In the end, the train crashes into the stuck vehicle, destroying it and sometimes even derailing the train. According to the Federal Railroad Administration, every year hundreds of vehicles meet this fate by trains, which can take over a mile to stop.

“I was just surprised at the number of these that I found,” Plant says. “For every accident that’s videotaped, there are probably many more.”

Inspired by a workplace safety class that preached a principle of minimizing the impact of accidents, Derek set about looking for solutions to the problem of trains hitting stuck vehicles.

Railroad tracks are elevated for proper drainage, and the humped profile of many crossings can cause a vehicle to bottom out. “Theoretically, we could lower all the crossings so that they’re no longer a hump. But there are 200,000 crossings in the United States,” Plant says. “Railroads and local governments are trying hard to minimize the number of these crossings by creating overpasses, or elevating roadways. That’s cost-prohibitive, and it’s not going to happen soon.”

Other solutions, such as re-engineering the suspension on vehicles likely to get stuck, seemed equally improbable.

After studying how railroad signaling systems work, Plant came up with an idea: to fake the presence of a train. His invention was developed in his spare time using techniques and principles he learned over his almost two decades at Fermilab. It is currently in the patent application process and being prosecuted by Fermilab’s Office of Technology Transfer.

“If you cross over a railroad track and you look down the tracks, you’ll see red or yellow or green lights,” he says. “Trains have traffic signals too.”

These signals are tied to signal blocks—segments of the tracks that range from a mile to several miles in length. When a train is on the tracks, its metal wheels and axle connect both rails, forming an electric circuit through the tracks to trigger the signals. These signals inform other trains not to proceed while one train occupies a block, avoiding pileups.

Plant thought, “What if other vehicles could trigger the same signal in an emergency?” By faking the presence of a train, a vehicle stuck on the tracks could give advanced warning for oncoming trains to stop and stall for time. Hence the name of Plant’s invention: the Ghost Train Generator.

To replicate the train’s presence, Plant knew he had to create a very strong electric current between the rails. The most straightforward way to do this is with massive amounts of metal, as a train does. But for the Ghost Train Generator to be useful in a pinch, it needs to be small, portable and easily applied. The answer to achieving these features lies in strong magnets and special wire.

“Put one magnet on one rail and one magnet on the other and the device itself mimics—electrically—what a train would look like to the signaling system,” he says. “In theory, this could be carried in vehicles that are at high risk for getting stuck on a crossing: semis, tour buses and first-response vehicles,” Plant says. “Keep it just like you would a fire extinguisher—just behind the seat or in an emergency compartment.”

Once the device is deployed, the train would receive the signal that the tracks were obstructed and stop. Then the driver of the stuck vehicle could call for emergency help using the hotline posted on all crossings.

Plant compares the invention to a seatbelt.

“Is it going to save your life 100 percent of the time? Nope, but smart people wear them,” he says. “It’s designed to prevent a collision when a train is more than two minutes from the crossing.”

And like a seatbelt, part of what makes Plant’s invention so appealing is its simplicity.

“The first thing I thought was that this is a clever invention,” says Aaron Sauers from Fermilab’s technology transfer office, who works with lab staff to develop new technologies for market. “It’s an elegant solution to an existing problem. I thought, ‘This technology could have legs.’”

The organizers of the National Innovation Summit seem to agree.  In May, Fermilab received an Innovation Award from TechConnect for the Ghost Train Generator. The invention will also be featured as a showcase technology in the upcoming Defense Innovation Summit in October.

The Ghost Train Generator is currently in the pipeline to receive a patent with help from Fermilab, and its prospects are promising, according to Sauers. It is a nonprovisional patent, which has specific claims and can be licensed. After that, if the generator passes muster and is granted a patent, Plant will receive a portion of the royalties that it generates for Fermilab.

Fermilab encourages a culture of scientific innovation and exploration beyond the field of particle physics, according to Sauers, who noted that Plant’s invention is just one of a number of technology transfer initiatives at the lab.

Plant agrees—Fermilab’s environment helped motivate his efforts to find a solution for railroad crossing accidents.

“It’s just a general problem-solving state of mind,” he says. “That’s the philosophy we have here at the lab.”

Editor's note: A version of this article was originally published by Fermilab.

Fermilab on display

Thu, 09/28/2017 - 17:47

The national laboratory opened usually inaccessible areas of its campus to thousands of visitors to celebrate 50 years of discovery.

Fermi National Accelerator Laboratory’s yearlong 50th anniversary celebration culminated on Saturday with an Open House that drew thousands of visitors despite the unseasonable heat.

On display were areas of the lab not normally open to guests, including neutrino and muon experiments, a portion of the accelerator complex, lab spaces and magnet and accelerator fabrication and testing areas, to name a few. There were also live links to labs around the world, including CERN, a mountaintop observatory in Chile, and the mile-deep Sanford Underground Research Facility that will house the international neutrino experiment, DUNE.

But it wasn’t all physics. In addition to hands-on demos and a STEM fair, visitors could also learn about Fermilab’s art and history, walk the prairie trails or hang out with the ever-popular bison. In all, some 10,000 visitors got to go behind-the-scenes at Fermilab, shuttled around on 80 buses and welcomed by 900 Fermilab workers eager to explain their roles at the lab. Below, see a few of the photos captured as Fermilab celebrated 50 years of discovery.

Fermilab employees Jemila Adetunji and Joel Kofron arrive on site excited to welcome thousands of visitors.

Fermilab photo archives

A section of the CMS detector at CERN is displayed on the side of a Fermilab building to provide visitors with a sense of scale. Fermilab is the US hub for CMS and helped design, fabricate and install the detector, as well as analyze the data.

Fermilab photo archives

Dozens of Chicagoland STEM institutions brought knowledge, hands-on activities and goodies to the STEM fair.

Fermilab photo archives

Those who visited the technical campus learned how Fermilab develops coils for powerful magnets used in particle physics research.

Fermilab photo archives

At the Cryomodule Test Facility, guests saw cryomodules (the building blocks of particle accelerators) and a cryoplant (that creates supercold fluids). They also got a taste of a cleanroom.

Fermilab photo archives

Tents erected for the celebration provided welcome shade from which to view the campus, including the tall Tractricious sculpture.

Fermilab photo archives

Hundreds of young scientists experimented with hands-on demos at the Lederman Science Center.

Fermilab photo archives

Guests pause for a photo in the tents outside of the Lederman Science Center.

Fermilab photo archives

Jerry Zimmerman, aka Mr. Freeze, gave four cool performances of his popular cryogenic show throughout the day, to the delight of audiences in Ramsey Auditorium.

Fermilab photo archives

The coolest place on site was in the underground tunnel that houses the Muon Delivery Ring and beamline for the Muon g-2 and Mu2e experiments.

Fermilab photo archives

The Muon g-2 experimenters added a few cartoon characters to help explain their science.

Fermilab photo archives

Visitors look down into the future home of the ICARUS detector, a neutrino hunter born in Italy that was recently refurbished at CERN.

Fermilab photo archives

Part of the volunteer team at the neutrino campus breaks from sharing science for an exuberant group photo.

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Shining with possibility

Tue, 09/26/2017 - 16:13

As Jordan-based SESAME nears its first experiments, member nations are connecting in new ways.

Early in the morning, physicist Roy Beck Barkai boards a bus in Tel Aviv bound for Jordan. By 10:30 a.m., he is on site at SESAME, a new scientific facility where scientists plan to use light to study everything from biology to archaeology. He is back home by 7 p.m., in time to have dinner with his children.

Before SESAME opened, the closest facility like it was in Italy. Beck Barkai often traveled for two days by airplane, train and taxi for a day or two of work—an inefficient and expensive process that limited his ability to work with specialized equipment from his home lab and required him to spend days away from his family.  

“For me, having the ability to kiss them goodbye in the morning and just before they went to sleep at night is a miracle,” Beck Barkai says. “It felt like a dream come true. Having SESAME at our doorstep is a big plus."

SESAME, also known as the International Centre for Synchrotron-Light for Experimental Science and Applications in the Middle East, opened its doors in May and is expected to host its first beams of particles this year. Scientists from around the world will be able to apply for time to use the facility’s powerful light source for their experiments. It’s the first synchrotron in the region and the first international research center in the Middle East. 

Beck Barkai says SESAME provides a welcome dose of convenience, as scientists in the region can now drive to a research center instead of flying with sensitive equipment to another country. It’s also more cost-effective.

Located in Jordan to the northwest of the city of Amman, SESAME was built by a collaboration made up of the countries of Cyprus, Egypt, Iran, Israel, Jordan, Pakistan, Turkey and the Palestinian Authority—a partnership members hope will improve relations among the eight neighbors.

“SESAME is a very important step in the region,” says SESAME Scientific Advisory Committee Chair Zehra Sayers. “The language of science is objective. It’s based on curiosity. It doesn’t need to be affected by the differences in cultural and social backgrounds in these countries. I hope it is something that we will leave the next generations as a positive step toward stability.”

Artwork by Ana Kova

Protein researcher and a University of Jordan professor Areej Abuhammad says she hopes SESAME will provide an environment that encourages collaboration. 

“I think through having the chance to interact, the scientists from around this region will learn to trust and respect each other,” she says. “I don’t think that this will result in solving all the problems in the region from one day to the next, but it will be a big step forward.”

The $100 million center is a state-of-the-art research facility that should provide some relief to scientists seeking time at other, overbooked facilities. SESAME plans to eventually host 100 to 200 users at a time. 

SESAME’s first two beamlines will open later this year. About twice per year, SESAME will announce calls for research proposals, the next of which is expected for this fall. Sayers says proposals will be evaluated for originality, preparedness and scientific quality. 

Groups of researchers hoping to join the first round of experiments submitted more than 50 applications. Once the lab is at full operation, Sayers says, the selection committee expects to receive four to five times more than that.

Opening up a synchrotron in the Middle East means that more people will learn about these facilities and have a chance to use them. Because some scientists in the region are new to using synchrotrons or writing the style of applications SESAME requires, Sayers asked the selection committee to provide feedback with any rejections. 

Abuhammad is excited for the learning opportunity SESAME presents for her students—and for the possibility that experiences at SESAME will spark future careers in science. 

She plans to apply for beam time at SESAME to conduct protein crystallography, a field that involves peering inside proteins to learn about their function and aid in pharmaceutical drug discovery. 

Another scientist vying for a spot at SESAME is Iranian chemist Maedeh Darzi, who studies the materials of ancient manuscripts and how they degrade. Synchrotrons are of great value to archaeologists because they minimize the damage to irreplaceable artifacts. Instead of cutting them apart, scientists can take a less damaging approach by probing them with particles. 

Darzi sees SESAME as a chance to collaborate with scientists from other Middle Eastern countries and promote science, peace and friendship. For her and others, SESAME could be a place where particles put things back together.

Concrete applications for accelerator science

Thu, 09/21/2017 - 19:18

A project called A2D2 will explore new applications for compact linear accelerators.

Particle accelerators are the engines of particle physics research at Fermi National Accelerator Laboratory. They generate nearly light-speed, subatomic particles that scientists study to get to the bottom of what makes our universe tick. Fermilab experiments rely on a number of different accelerators, including a powerful, 500-foot-long linear accelerator that kick-starts the process of sending particle beams to various destinations.

But if you’re not doing physics research, what’s an accelerator good for?

It turns out, quite a lot: Electron beams generated by linear accelerators have all kinds of practical uses, such as making the wires used in cars melt-resistant or purifying water.

A project called Accelerator Application Development and Demonstration (A2D2) at Fermilab’s Illinois Accelerator Research Center will help Fermilab and its partners to explore new applications for compact linear accelerators, which are only a few feet long rather than a few hundred. These compact accelerators are of special interest because of their small size—they’re cheaper and more practical to build in an industrial setting than particle physics research accelerators—and they can be more powerful than ever.

“A2D2 has two aspects: One is to investigate new applications of how electron beams might be used to change, modify or process different materials,” says Fermilab’s Tom Kroc, an A2D2 physicist. “The second is to contribute a little more to the understanding of how these processes happen.”

To develop these aspects of accelerator applications, A2D2 will employ a compact linear accelerator that was once used in a hospital to treat tumors with electron beams. With a few upgrades to increase its power, the A2D2 accelerator will be ready to embark on a new venture: exploring and benchmarking other possible uses of electron beams, which will help specify the design of a new, industrial-grade, high-power machine under development by IARC and its partners.

It won’t be just Fermilab scientists using the A2D2 accelerator: As part of IARC, the accelerator will be available for use (typically through a formal CRADA or SPP agreement) by anyone who has a novel idea for electron beam applications. IARC’s purpose is to partner with industry to explore ways to translate basic research and tools, including accelerator research, into commercial applications.

“I already have a lot of people from industry asking me, ‘When can I use A2D2?’” says Charlie Cooper, general manager of IARC. “A2D2 will allow us to directly contribute to industrial applications—it’s something concrete that IARC now offers.”

Speaking of concrete, one of the first applications in mind for compact linear accelerators is creating durable pavement for roads that won’t crack in the cold or spread out in the heat. This could be achieved by replacing traditional asphalt with a material that could be strengthened using an accelerator. The extra strength would come from crosslinking, a process that creates bonds between layers of material, almost like applying glue between sheets of paper. A single sheet of paper tears easily, but when two or more layers are linked by glue, the paper becomes stronger.

“Using accelerators, you could have pavement that lasts longer, is tougher and has a bigger temperature range,” says Bob Kephart, director of IARC. Kephart holds two patents for the process of curing cement through crosslinking. “Basically, you’d put the road down like you do right now, and you’d pass an accelerator over it, and suddenly you’d turn it into really tough stuff—like the bed liner in the back of your pickup truck.”

This process has already caught the eye of the U.S. Army Corps of Engineers, which will be one of A2D2’s first partners. Another partner will be the Chicago Metropolitan Water Reclamation District, which will test the utility of compact accelerators for water purification. Many other potential customers are lining up to use the A2D2 technology platform.

“You can basically drive chemical reactions with electron beams—and in many cases those can be more efficient than conventional technology, so there are a variety of applications,” Kephart says. “Usually what you have to do is make a batch of something and heat it up in order for a reaction to occur. An electron beam can make a reaction happen by breaking a bond with a single electron.”

In other words, instead of having to cook a material for a long time to reach a specific heat that would induce a chemical reaction, you could zap it with an electron beam to get the same effect in a fraction of the time.

In addition to exploring the new electron-beam applications with the A2D2 accelerator, scientists and engineers at IARC are using cutting-edge accelerator technology to design and build a new kind of portable, compact accelerator, one that will take applications uncovered with A2D2 out of the lab and into the field. The A2D2 accelerator is already small compared to most accelerators, but the latest R&D allows IARC experts to shrink the size while increasing the power of their proposed accelerator even further.

“The new, compact accelerator that we’re developing will be high-power and high-energy for industry,” Cooper says. “This will enable some things that weren’t possible in the past. For something such as environmental cleanup, you could take the accelerator directly to the site.”

While the IARC team develops this portable accelerator, which should be able to fit on a standard trailer, the A2D2 accelerator will continue to be a place to experiment with how to use electron beams—and study what happens when you do.

“The point of this facility is more development than research, however there will be some research on irradiated samples,” says Fermilab’s Mike Geelhoed, one of the A2D2 project leads. “We’re all excited—at least I am. We and our partners have been anticipating this machine for some time now. We all want to see how well it can perform.”

Editor's note: This article was originally published by Fermilab.

50 years of stories

Tue, 09/19/2017 - 15:00

To celebrate a half-century of discovery, Fermilab has been gathering tales of life at the lab.

Science stories usually catch the eye when there’s big news: the discovery of gravitational waves, the appearance of a new particle. But behind the blockbusters are the thousands of smaller stories of science behind the scenes and daily life at a research institution. 

As the Department of Energy’s Fermi National Accelerator Laboratory celebrates its 50th anniversary year, employees past and present have shared memories of building a lab dedicated to particle physics.

Some shared personal memories: keeping an accelerator running during a massive snowstorm; being too impatient for the arrival of an important piece of detector equipment to stay put and wait for it to arrive; accidentally complaining about the lab to the lab’s director.

Others focused on milestones and accomplishments: the first daycare at a national lab, the Saturday Morning Physics Program built by Nobel laureate Leon Lederman, the birth of the web at Fermilab.

People shared memories of big names that built the lab: charismatic founding director Robert R. Wilson, fiery head of accelerator development Helen Edwards, talented lab artist Angela Gonzales.

And or course, employees told stories about Fermilab’s resident herd of bison.

There are many more stories to peruse. You can watch a playlist of the video anecdotes or find all of the stories (both written and video) collected on Fermilab’s 50th anniversary website.

SENSEI searches for light dark matter

Fri, 09/15/2017 - 21:00

Technology proposed 30 years ago to search for dark matter is finally seeing the light.

In a project called SENSEI, scientists are using innovative sensors developed over three decades to look for the lightest dark matter particles anyone has ever tried to detect.

Dark matter—so named because it doesn’t absorb, reflect or emit light—constitutes 27 percent of the universe, but the jury is still out on what it’s made of. The primary theoretical suspect for the main component of dark matter is a particle scientists have descriptively named the weakly interactive massive particle, or WIMP.

But since none of these heavy particles, which are expected to have a mass 100 times that of a proton, have shown up in experiments, it might be time for researchers to think small.

“There is a growing interest in looking for different kinds of dark matter that are additives to the standard WIMP model,” says Fermi National Accelerator Laboratory scientist Javier Tiffenberg, a leader of the SENSEI collaboration. “Lightweight, or low-mass, dark matter is a very compelling possibility, and for the first time, the technology is there to explore these candidates.”

Sensing the unseen

In traditional dark matter experiments, scientists look for a transfer of energy that would occur if dark matter particles collided with an ordinary nucleus. But SENSEI is different; it looks for direct interactions of dark matter particles colliding with electrons.

“That is a big difference—you get a lot more energy transferred in this case because an electron is so light compared to a nucleus,” Tiffenberg says.

If dark matter had low mass—much smaller than the WIMP model suggests—then it would be many times lighter than an atomic nucleus. So if it were to collide with a nucleus, the resulting energy transfer would be far too small to tell us anything. It would be like throwing a ping-pong ball at a boulder: The heavy object wouldn’t go anywhere, and there would be no sign the two had come into contact.

An electron is nowhere near as heavy as an atomic nucleus. In fact, a single proton has about 1836 times more mass than an electron. So the collision of a low-mass dark matter particle with an electron has a much better chance of leaving a mark—it’s more bowling ball than boulder.

Bowling balls aren't exactly light, though. An energy transfer between a low-mass dark matter particle and an electron would leave only a blip of energy, one either too small for most detectors to pick up or easily overshadowed by noise in the data.

“The bowling ball will move a very tiny amount,” says Fermilab scientist Juan Estrada, a SENSEI collaborator. “You need a very precise detector to see this interaction of lightweight particles with something that is much heavier.”

That’s where SENSEI’s sensitive sensors come in.

SENSEI will use skipper charge-couple devices, also called skipper CCDs. CCDs have been used for other dark matter detection experiments, such as the Dark Matter in CCDs (or DAMIC) experiment operating at SNOLAB in Canada. These CCDs were a spinoff from sensors developed for use in the Dark Energy Camera in Chile and other dark energy search projects.

CCDs are typically made of silicon divided into pixels. When a dark matter particle passes through the CCD, it collides with the silicon’s electrons, knocking them free, leaving a net electric charge in each pixel the particle passes through. The electrons then flow through adjacent pixels and are ultimately read as a current in a device that measures the number of electrons freed from each CCD pixel. That measurement tells scientists about the mass and energy of the particle that got the chain reaction going. A massive particle, like a WIMP, would free a gusher of electrons, but a low-mass particle might free only one or two.

Typical CCDs can measure the charge left behind only once, which makes it difficult to decide if a tiny energy signal from one or two electrons is real or an error.

Skipper CCDs are a new generation of the technology that helps eliminate the “iffiness” of a measurement that has a one- or two-electron margin of error. “The big step forward for the skipper CCD is that we are able to measure this charge as many times as we want,” Tiffenberg says.

The charge left behind in the skipper CCD can be sampled multiple times and then averaged, a method that yields a more precise measurement of the charge deposited in each pixel than the measure-one-and-done technique. That’s the rule of statistics: With more data, you get closer to a property’s true value.

SENSEI scientists take advantage of the skipper CCD architecture, measuring the number of electrons in a single pixel a whopping 4000 times.

“This is a simple idea, but it took us 30 years to get it to work,” Estrada says.

From idea to reality to beyond

A small SENSEI prototype is currently running at Fermilab in a detector hall 385 feet below ground, and it has demonstrated that this detector design will work in the hunt for dark matter.

Skipper CCD technology and SENSEI were brought to life by Laboratory Directed Research and Development (LDRD) funds at Fermilab and Lawrence Berkeley National Laboratory (Berkeley Lab). LDRD programs are intended to provide funding for development of novel, cutting-edge ideas for scientific discovery.

The Fermilab LDRDs were awarded only recently—less than two years ago—but close collaboration between the two laboratories has already yielded SENSEI’s promising design, partially thanks to Berkeley lab’s previous work in skipper CCD design.

Fermilab LDRD funds allow researchers to test the sensors and develop detectors based on the science, and the Berkeley Lab LDRD funds support the sensor design, which was originally proposed by Berkeley Lab scientist Steve Holland.

“It is the combination of the two LDRDs that really make SENSEI possible,” Estrada says.

Future SENSEI research will also receive a boost thanks to a recent grant from the Heising-Simons Foundation.

“SENSEI is very cool, but what’s really impressive is that the skipper CCD will allow the SENSEI science and a lot of other applications,” Estrada says. “Astronomical studies are limited by the sensitivity of their experimental measurements, and having sensors without noise is the equivalent of making your telescope bigger—more sensitive.”

SENSEI technology may also be critical in the hunt for a fourth type of neutrino, called the sterile neutrino, which seems to be even more shy than its three notoriously elusive neutrino family members.

A larger SENSEI detector equipped with more skipper CCDs will be deployed within the year. It’s possible it might not detect anything, sending researchers back to the drawing board in the hunt for dark matter. Or SENSEI might finally make contact with dark matter—and that would be SENSEI-tional.

Editor's note: This article is based on an article published by Fermilab.

Clearing a path to the stars

Tue, 09/12/2017 - 15:00

Astronomers are at the forefront of the fight against light pollution, which can obscure our view of the cosmos.

More than a mile up in the San Gabriel Mountains in Los Angeles County sits the Mount Wilson Observatory, once one of the cornerstones of groundbreaking astronomy. 

Founded in 1904, it was twice home to the largest telescope on the planet, first with its 60-inch telescope in 1908, followed by its 100-inch telescope in 1917. In 1929, Edwin Hubble revolutionized our understanding of the shape of the universe when he discovered on Mt. Wilson that it was expanding. 

But a problem was radiating from below. As the city of Los Angeles grew, so did the reach and brightness of its skyglow, otherwise known as light pollution. The city light overpowered the photons coming from faint, distant objects, making deep-sky cosmology all but impossible. In 1983, the Carnegies, who had owned the observatory since its inception, abandoned Mt. Wilson to build telescopes in Chile instead.

“They decided that if they were going to do greater, more detailed and groundbreaking science in astronomy, they would have to move to a dark place in the world,” says Tom Meneghini, the observatory’s executive director. “They took their money and ran.” 

(Meneghini harbors no hard feelings: “I would have made the same decision,” he says.)

Beyond being a problem for astronomers, light pollution is also known to harm and kill wildlife, waste energy and cause disease in humans around the globe. For their part, astronomers have worked to convince local governments to adopt better lighting ordinances, including requiring the installation of fixtures that prevent light from seeping into the sky. 

Artwork by Corinne Mucha

Many towns and cities are already reexamining their lighting systems as the industry standard shifts from sodium lights to light-emitting diodes, or LEDs, which last longer and use far less energy, providing both cost-saving and environmental benefits. But not all LEDs are created equal. Different bulbs emit different colors, which correspond to different temperatures. The higher the temperature, the bluer the color. 

The creation of energy-efficient blue LEDs was so profound that its inventors were awarded the 2014 Nobel Prize in Physics. But that blue light turns out to be particularly detrimental to astronomers, for the same reason that the daytime sky is blue: Blue light scatters more than any other color. (Blue lights have also been found to be more harmful to human health than more warmly colored, amber LEDs. In 2016, the American Medical Association issued guidance to minimize blue-rich light, stating that it disrupts circadian rhythms and leads to sleep problems, impaired functioning and other issues.)

The effort to darken the skies has expanded to include a focus on LEDs, as well as an attempt to get ahead of the next industry trend. 

At a January workshop at the annual American Astronomical Society (AAS) meeting, astronomer John Barentine sought to share stories of towns and cities that had successfully battled light pollution. Barentine is a program manager for the International Dark-Sky Association (IDA), a nonprofit founded in 1988 to combat light pollution. He pointed to the city of Phoenix, Arizona. 

Arizona is a leader in reducing light pollution. The state is home to four of the 10 IDA-recognized “Dark Sky Communities” in the United States. “You can stand in the middle of downtown Flagstaff and see the Milky Way,” says James Lowenthal, an astronomy professor at Smith College.

But it’s not immune to light pollution. Arizona’s Grand Canyon National Park is designated by the IDA as an International Dark Sky Park, and yet, on a clear night, Barentine says, the horizon is stained by the glow of Las Vegas 170 miles away.

Artwork by Corinne Mucha

In 2015, Phoenix began testing the replacement of some of its 100,000 or so old streetlights with LEDs, which the city estimated would save $2.8 million a year in energy bills. But they were using high-temperature blue LEDs, which would have bathed the city in a harsh white light. 

Through grassroots work, the local IDA chapter delayed the installation for six months, giving the council time to brush up on light pollution and hear astronomers’ concerns. In the end, the city went beyond IDA’s “best expectations,” Barentine says, opting for lights that burn at a temperature well under IDA’s maximum recommendations. 

“All the way around, it was a success to have an outcome arguably influenced by this really small group of people, maybe 10 people in a city of 2 million,” he says. “People at the workshop found that inspiring.”

Just getting ordinances on the books does not necessarily solve the problem, though. Despite enacting similar ordinances to Phoenix, the city of Northampton, Massachusetts, does not have enough building inspectors to enforce them. “We have this great law, but developers just put their lights in the wrong way and nobody does anything about it,” Lowenthal says. 

For many cities, a major part of the challenge of combating light pollution is simply convincing people that it is a problem. This is particularly tricky for kids who have never seen a clear night sky bursting with bright stars and streaked by the glow of the Milky Way, says Connie Walker, a scientist at the National Optical Astronomy Observatory who is also on the board of the IDA. “It’s hard to teach somebody who doesn’t know what they’ve lost,” Walker says.

Walker is focused on making light pollution an innate concern of the next generation, the way campaigns in the 1950s made littering unacceptable to a previous generation of kids. 

In addition to creating interactive light-pollution kits for children, the NOAO operates a citizen-science initiative called Globe at Night, which allows anyone to take measurements of brightness in their area and upload them to a database. To date, Globe at Night has collected more than 160,000 observations from 180 countries. 

It’s already produced success stories. In Norman, Oklahoma, for example, a group of high school students, with the assistance of amateur astronomers, used Globe at Night to map light pollution in their town. They took the data to the city council. Within two years, the town had passed stricter lighting ordinances. 

“Light pollution is foremost on our minds because our observatories are at risk,” Walker says. “We should really be concentrating on the next generation.”

Detectors in the dirt

Fri, 09/08/2017 - 18:40

A humidity and temperature monitor developed for CMS finds a new home in Lebanon.

People who tend crops in Lebanon and people who tend particle detectors on the border of France and Switzerland have a need in common: large-scale humidity and temperature monitoring. A scientist who noticed this connection is working with farmers to try to use a particle physics solution to solve an agricultural problem.

Farmers, especially those in dry areas found in the Middle East, need to produce as much food as possible without using too much water. Scientists on experiments at the Large Hadron Collider want to track the health of their detectors—a sudden change in humidity or temperature can indicate a problem.

To monitor humidity and temperature in their detector, members of the CMS experiment at the LHC developed a fiber-optic system. Fiber optics are wires made from glass that can carry light. Etching small mirrors into the core of a fiber creates a “Bragg grating,” a system that either lets light through or reflects it back, based on its wavelength and the distance between the mirrors.

“Temperature will naturally have an impact on the distance between the mirrors because of the contraction and dilation of the material,” says Martin Gastal, a member of the CMS collaboration at the LHC. “By default, a Bragg grating sensor is a temperature sensor.”

Scientists at the University of Sannio and INFN Naples developed a material for the CMS experiment that could turn the temperature sensors into humidity monitors as well. The material expands when it comes into contact with water, and the expansion pulls the mirrors apart. The sensors were tested by a team from the Experimental Physics Department at CERN.

In December 2015, Lebanon signed an International Cooperation Agreement with CERN, and the Lebanese University joined CMS. As Professor Haitham Zaraket, a theoretical physicist at the Lebanese University and member of the CMS experiment, recalls, they picked fiber optic monitoring from a list of CMS projects for one of their engineers to work on. Martin then approached them about the possibility of applying the technology elsewhere.

With Lebanon’s water resources under increasing pressure from a growing population and agricultural needs, irrigation control seemed like a natural application. “Agriculture consumes quite a high amount of water, of fresh water, and this is the target of this project,” says Ihab Jomaa, the Department Head of Irrigation and Agrometeorology at the Lebanese Agricultural Research Institute. “We are trying to raise what we call in agriculture lately ‘water productivity.’”

The first step after formally establishing the Fiber Optic Sensor Systems for Irrigation (FOSS4I) collaboration was to make sure that the sensors could work at all in Lebanon’s clay-heavy soil. The Lebanese University shipped 10 kilograms of soil from Lebanon to Naples, where collaborators at University of Sannio adjusted the sensor design to increase the measurement range.

During phase one, which lasted from March to June, 40 of the sensors were used to monitor a small field in Lebanon. It was found that, contrary to the laboratory findings, they could not in practice sense the full range of soil moisture content that they needed to. Based on this feedback, “we are working on a new concept which is not just a simple modification of the initial architecture,” Haitham says. The new design concept is to use fiber optics to monitor an absorbing material planted in the soil rather than having a material wrapped around the fiber.

“We are reinventing the concept,” he says. “This should take some time and hopefully at the end of it we will be able to go for field tests again.” At the same time, they are incorporating parts of phase three, looking for soil parameters such as pesticide or chemicals inside the soil or other bacterial effects.

If the new concept is successfully validated, the collaboration will move on to testing more fields and more crops. Research and development always involves setbacks, but the FOSS4I collaboration has taken this one as an opportunity to pivot to a potentially even more powerful technology.

What can particles tell us about the cosmos?

Tue, 09/05/2017 - 16:18

The minuscule and the immense can reveal quite a bit about each other.

In particle physics, scientists study the properties of the smallest bits of matter and how they interact. Another branch of physics—astrophysics—creates and tests theories about what’s happening across our vast universe.

While particle physics and astrophysics appear to focus on opposite ends of a spectrum, scientists in the two fields actually depend on one another. Several current lines of inquiry link the very large to the very small.

The seeds of cosmic structure

For one, particle physicists and astrophysicists both ask questions about the growth of the early universe. 

In her office at Stanford University, Eva Silverstein explains her work parsing the mathematical details of the fastest period of that growth, called cosmic inflation. 

“To me, the subject is particularly interesting because you can understand the origin of structure in the universe,” says Silverstein, a professor of physics at Stanford and the Kavli Institute for Particle Astrophysics and Cosmology. “This paradigm known as inflation accounts for the origin of structure in the most simple and beautiful way a physicist can imagine.” 

Scientists think that after the Big Bang, the universe cooled, and particles began to combine into hydrogen atoms. This process released previously trapped photons—elementary particles of light. 

The glow from that light, called the cosmic microwave background, lingers in the sky today. Scientists measure different characteristics of the cosmic microwave background to learn more about what happened in those first moments after the Big Bang.

According to scientists’ models, a pattern that first formed on the subatomic level eventually became the underpinning of the structure of the entire universe. Places that were dense with subatomic particles—or even just virtual fluctuations of subatomic particles—attracted more and more matter. As the universe grew, these areas of density became the locations where galaxies and galaxy clusters formed. The very small grew up to be the very large.

Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

“It’s amazing that we can probe what was going on almost 14 billion years ago,” Silverstein says. “We can’t learn everything that was going on, but we can still learn an incredible amount about the contents and interactions.”

For many scientists, “the urge to trace the history of the universe back to its beginnings is irresistible,” wrote theoretical physicist Stephen Weinberg in his 1977 book The First Three Minutes. The Nobel laureate added, “From the start of modern science in the sixteenth and seventeenth centuries, physicists and astronomers have returned again and again to the problem of the origin of the universe.”

Searching in the dark

Particle physicists and astrophysicists both think about dark matter and dark energy. Astrophysicists want to know what made up the early universe and what makes up our universe today. Particle physicists want to know whether there are undiscovered particles and forces out there for the finding.

“Dark matter makes up most of the matter in the universe, yet no known particles in the Standard Model [of particle physics] have the properties that it should possess,” says Michael Peskin, a professor of theoretical physics at SLAC. “Dark matter should be very weakly interacting, heavy or slow-moving, and stable over the lifetime of the universe.”

There is strong evidence for dark matter through its gravitational effects on ordinary matter in galaxies and clusters. These observations indicate that the universe is made up of roughly 5 percent normal matter, 25 percent dark matter and 70 percent dark energy. But to date, scientists have not directly observed dark energy or dark matter.

“This is really the biggest embarrassment for particle physics,” Peskin says. “However much atomic matter we see in the universe, there’s five times more dark matter, and we have no idea what it is.” 

But scientists have powerful tools to try to understand some of these unknowns. Over the past several years, the number of models of dark matter has been expanding, along with the number of ways to detect it, says Tom Rizzo, a senior scientist at SLAC and head of the theory group.

Some experiments search for direct evidence of a dark matter particle colliding with a matter particle in a detector. Others look for indirect evidence of dark matter particles interfering in other processes or hiding in the cosmic microwave background. If dark matter has the right properties, scientists could potentially create it in a particle accelerator such as the Large Hadron Collider.

Physicists are also actively hunting for signs of dark energy. It is possible to measure the properties of dark energy by observing the motion of clusters of galaxies at the largest distances that we can see in the universe.

“Every time that we learn a new technique to observe the universe, we typically get lots of surprises,” says Marcelle Soares-Santos, a Brandeis University professor and a researcher on the Dark Energy Survey. “And we can capitalize on these new ways of observing the universe to learn more about cosmology and other sides of physics.”

Artwork by Ana Kova Forces at play

Particle physicists and astrophysicists find their interests also align in the study of gravity. For particle physicists, gravity is the one basic force of nature that the Standard Model does not quite explain. Astrophysicists want to understand the important role gravity played and continues to play in the formation of the universe.

In the Standard Model, each force has what’s called a force-carrier particle or a boson. Electromagnetism has photons. The strong force has gluons. The weak force has W and Z bosons. When particles interact through a force, they exchange these force-carriers, transferring small amounts of information called quanta, which scientists describe through quantum mechanics. 

General relativity explains how the gravitational force works on large scales: Earth pulls on our own bodies, and planetary objects pull on each other. But it is not understood how gravity is transmitted by quantum particles. 

Discovering a subatomic force-carrier particle for gravity would help explain how gravity works on small scales and inform a quantum theory of gravity that would connect general relativity and quantum mechanics. 

Compared to the other fundamental forces, gravity interacts with matter very weakly, but the strength of the interaction quickly becomes larger with higher energies. Theorists predict that at high enough energies, such as those seen in the early universe, quantum gravity effects are as strong as the other forces. Gravity played an essential role in transferring the small-scale pattern of the cosmic microwave background into the large-scale pattern of our universe today.

“Another way that these effects can become important for gravity is if there’s some process that lasts a long time,” Silverstein says. “Even if the energies aren’t as high as they would need to be sensitive to effects like quantum gravity instantaneously.” 

Physicists are modeling gravity over lengthy time scales in an effort to reveal these effects.

Our understanding of gravity is also key in the search for dark matter. Some scientists think that dark matter does not actually exist; they say the evidence we’ve found so far is actually just a sign that we don’t fully understand the force of gravity.  

Big ideas, tiny details

Learning more about gravity could tell us about the dark universe, which could also reveal new insight into how structure in the universe first formed. 

Scientists are trying to “close the loop” between particle physics and the early universe, Peskin says. As scientists probe space and go back further in time, they can learn more about the rules that govern physics at high energies, which also tells us something about the smallest components of our world.

Artwork for this article is available as a printable poster.

Neural networks meet space

Wed, 08/30/2017 - 19:08

Artificial intelligence analyzes gravitational lenses 10 million times faster.

Researchers from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have for the first time shown that neural networks—a form of artificial intelligence—can accurately analyze the complex distortions in spacetime known as gravitational lenses 10 million times faster than traditional methods.

“Analyses that typically take weeks to months to complete, that require the input of experts and that are computationally demanding, can be done by neural nets within a fraction of a second, in a fully automated way and, in principle, on a cell phone’s computer chip,” says postdoctoral fellow Laurence Perreault Levasseur, a co-author of a study published today in Nature.

Lightning-fast complex analysis

The team at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), a joint institute of SLAC and Stanford, used neural networks to analyze images of strong gravitational lensing, where the image of a faraway galaxy is multiplied and distorted into rings and arcs by the gravity of a massive object, such as a galaxy cluster, that’s closer to us. The distortions provide important clues about how mass is distributed in space and how that distribution changes over time – properties linked to invisible dark matter that makes up 85 percent of all matter in the universe and to dark energy that’s accelerating the expansion of the universe.

Until now this type of analysis has been a tedious process that involves comparing actual images of lenses with a large number of computer simulations of mathematical lensing models. This can take weeks to months for a single lens.

But with the neural networks, the researchers were able to do the same analysis in a few seconds, which they demonstrated using real images from NASA’s Hubble Space Telescope and simulated ones.

To train the neural networks in what to look for, the researchers showed them about half a million simulated images of gravitational lenses for about a day. Once trained, the networks were able to analyze new lenses almost instantaneously with a precision that was comparable to traditional analysis methods. In a separate paper, submitted to The Astrophysical Journal Letters, the team reports how these networks can also determine the uncertainties of their analyses.

KIPAC researchers used images of strongly lensed galaxies taken with the Hubble Space Telescope to test the performance of neural networks, which promise to speed up complex astrophysical analyses tremendously.

Yashar Hezaveh/Laurence Perreault Levasseur/Phil Marshall/Stanford/SLAC National Accelerator Laboratory; NASA/ESA Prepared for the data floods of the future

“The neural networks we tested—three publicly available neural nets and one that we developed ourselves—were able to determine the properties of each lens, including how its mass was distributed and how much it magnified the image of the background galaxy,” says the study’s lead author Yashar Hezaveh, a NASA Hubble postdoctoral fellow at KIPAC.

This goes far beyond recent applications of neural networks in astrophysics, which were limited to solving classification problems, such as determining whether an image shows a gravitational lens or not.

The ability to sift through large amounts of data and perform complex analyses very quickly and in a fully automated fashion could transform astrophysics in a way that is much needed for future sky surveys that will look deeper into the universe—and produce more data—than ever before.

The Large Synoptic Survey Telescope (LSST), for example, whose 3.2-gigapixel camera is currently under construction at SLAC, will provide unparalleled views of the universe and is expected to increase the number of known strong gravitational lenses from a few hundred today to tens of thousands.

“We won’t have enough people to analyze all these data in a timely manner with the traditional methods,” Perreault Levasseur says. “Neural networks will help us identify interesting objects and analyze them quickly. This will give us more time to ask the right questions about the universe.”

Scheme of an artificial neural network, with individual computational units organized into hundreds of layers. Each layer searches for certain features in the input image (at left). The last layer provides the result of the analysis. The researchers used particular kinds of neural networks, called convolutional neural networks, in which individual computational units (neurons, gray spheres) of each layer are also organized into 2-D slabs that bundle information about the original image into larger computational units.

Greg Stewart, SLAC National Accelerator Laboratory A revolutionary approach

Neural networks are inspired by the architecture of the human brain, in which a dense network of neurons quickly processes and analyzes information.

In the artificial version, the “neurons” are single computational units that are associated with the pixels of the image being analyzed. The neurons are organized into layers, up to hundreds of layers deep. Each layer searches for features in the image. Once the first layer has found a certain feature, it transmits the information to the next layer, which then searches for another feature within that feature, and so on.

“The amazing thing is that neural networks learn by themselves what features to look for,” says KIPAC staff scientist Phil Marshall, a co-author of the paper. “This is comparable to the way small children learn to recognize objects. You don’t tell them exactly what a dog is; you just show them pictures of dogs.”

But in this case, Hezaveh says, “It’s as if they not only picked photos of dogs from a pile of photos, but also returned information about the dogs’ weight, height and age.”

Although the KIPAC scientists ran their tests on the Sherlock high-performance computing cluster at the Stanford Research Computing Center, they could have done their computations on a laptop or even on a cell phone, they said. In fact, one of the neural networks they tested was designed to work on iPhones.

“Neural nets have been applied to astrophysical problems in the past with mixed outcomes,” says KIPAC faculty member Roger Blandford, who was not a co-author on the paper. “But new algorithms combined with modern graphics processing units, or GPUs, can produce extremely fast and reliable results, as the gravitational lens problem tackled in this paper dramatically demonstrates. There is considerable optimism that this will become the approach of choice for many more data processing and analysis problems in astrophysics and other fields.”    

Editor's note: This article originally appeared as a SLAC press release.

The dance of the particles

Tue, 08/29/2017 - 19:26

In collaboration with a scientist, an Iranian dancer is working to communicate the beauty of particle physics through dance.

 

Although CERN physicist Andrea Latina had always been interested in the arts, he had never really thought about dance before. 

While at a local film festival in 2015, he happened upon a flyer that quoted Persian poet Rumi about the “dance of particles.” Curious, he reached out to its author, Iranian dancer and choreographer Sahar Dehghan, to learn more.

Dehghan says that even as a child she was fascinated by both physics and dance. 

When she moved to France at a young age, she started taking dance classes, focusing on a meditative form called Sufi dancing and later concentrating on contemporary dance. But she also kept her fascination with physics, reading books and articles and having conversations with scientists she befriended in Paris as a young adult. 

“I became interested in quantum mechanics and its relation to physics, and I really started experimenting physically in my dance with a lot of these concepts,” she says.

Dehghan and Latina developed a friendship, meeting to chat about physics and dance. 

Virtual particles

Dehghan says that she was inspired by ideas such as the confinement of quarks via the strong force. 

“If you try to separate quarks, this force will be so strong that new particles will be created to prevent separation,” Latina says. “The density of energy is so high that a new pair of quark and antiquark will form so that the new quarks pair up with the original ones, just to avoid there being a single quark isolated in nature.”

In the winter of 2016, Dehghan visited CERN to learn more about its goals and how scientists are working to achieve them. One of the most inspiring things, she says, was seeing thousands of scientists from different backgrounds uniting to further our understanding of the universe.

“There are more than 11,000 people of more than 110 nationalities coming together with a common goal,” she says. “Instead of seeing superficial differences caused by cultural, religious, political or sexual preference, they respect and collaborate with each other, learning from each other for a greater purpose.”

Latina says that conversations with Dehghan gave him insight into physics as well. 

“I’m very enthusiastic about CERN and my work,” he says. “In drawing parallels between ancient philosophies, Sahar reminded me that what we are doing is the same thing humans have been doing for millennia: questioning where we come from, where we are going and what our role in the universe is. She was able to evoke this ancestral wonder and help me rediscover the poetry of what we do at CERN. We are incessantly trying to answer the same questions; we just use different tools and the language of mathematics.” 

Dehghan says she would love to communicate these themes through dance. Through artistic mediums, she says, new ideas can be heard, seen and felt in a deeper, more meaningful way.

“It would be great if we could all see beyond our own illusions into the fascinating particle interactions happening in everything and everyone at all times and the true unity that connects us in this great quantum dance, whirling at all times in rhythm with the music of the entire cosmos,” she says.

She has begun to choreograph a show called WHIRL Quantum Dance. Through scenes in her show, she tries to illustrate concepts such as quantum chromodynamics (with colored lights) or quantum entanglement (with pairs of dancers). She is even trying to create a collision scene with spinning dancers in a large circle representing an accelerator.

“I am not a scientific expert in anything so I am not trying to teach anyone,” she says. “What I want to do with this show is open some doors for the audience to go out there and search for more and learn about not just about quantum and particle physics, but also go out there and physically experiment and see how we’re all connected. 

“Even if I open just one door for one person in the audience to go in that direction, I will have achieved my goal.”

WHIRL: Quantum Dance, which is being presented by Sangram Arts, will premiere in the San Francisco Bay Area at the School of Arts & Culture at Mexican Heritage Plaza on September 22 and 23, with dancers Shahrokh Moshkin Ghalam and Rakesh Sukesh. Dehghan says that she hopes to make a film of the show to tour at different venues in cities around the world.

For more information, visit Dehghan's Facebook page.

Mega-collaborations for scientific discovery

Thu, 08/24/2017 - 17:45

DUNE joins the elite club of physics collaborations with more than 1000 members.

Sometimes it takes lot of people working together to make discovery possible. More than 7000 scientists, engineers and technicians worked on designing and constructing the Large Hadron Collider at CERN, and thousands of scientists now run each of the LHC’s four major experiments.

Not many experiments garner such numbers. On August 15, the Deep Underground Neutrino Experiment (DUNE) became the latest member of the exclusive clique of particle physics experiments with more than a thousand collaborators.

Meet them all:

Photo by Maximilien Brice, CERN 4,000+: Compact Muon Solenoid Detector (CMS) Experiment

CMS is one of the two largest experiments at the LHC. It is best known for its role in the discovery of the Higgs boson.

The “C” in CMS stands for compact, but there’s nothing compact about the CMS collaboration. It is one of the largest scientific collaborations in history. More than 4000 people from 200 institutions around the world work on the CMS detector and use its data for research.

About 30 percent of the CMS collaboration hail from US institutions. A remote operations center at the Department of Energy’s Fermi National Accelerator Laboratory in Batavia, Illinois, serves as a base for CMS research in the United States.

Claudia Marcelloni, CERN 3,000+: A Toroidal LHC ApparatuS (ATLAS) Experiment

The ATLAS experiment, the other large experiment responsible for discovering the Higgs boson at the LHC, ranks number two in number of collaborators. The ATLAS collaboration has more than 3000 members from 182 institutions in 38 countries. ATLAS and CMS ask similar questions about the building blocks of the universe, but they look for the answers with different detector designs. 

About 30 percent of the ATLAS collaboration are from institutions in the United States. Brookhaven National Laboratory in Upton, New York, serves as the US host.

2,000+: Linear Collider Collaboration

The Linear Collider Collaboration (LCC) is different from CMS and ATLAS in that the collaboration’s experiment is still a proposed project and has not yet been built. LCC has around 2000 members who are working to develop and build a particle collider that can produce different kinds of collisions than those seen at the LHC.

LCC members are working on two potential linear collider projects: the compact linear collider study (CLIC) at CERN and the International Linear Collider (ILC) in Japan. CLIC and the ILC originally began as separate projects, but the scientists working on both joined forces in 2013.

Either CLIC or the ILC would complement the LHC by colliding electrons and positrons to explore the Higgs particle interactions and the nature of subatomic forces in greater detail.

Antonio Saba, CERN 1,500+; A Large Ion Collider Experiment (ALICE)

ALICE is part of LHC’s family of particle detectors, and, like ATLAS and CMS, it too has a large, international collaboration, counting 1500 members from 154 physics institutes in 37 countries. Research using ALICE is focused on quarks, the sub-atomic particles that make up protons and neutrons, and the strong force responsible for holding quarks together.

Courtesy of Fermilab 1,000+: Deep Underground Neutrino Experiment (DUNE)

The Deep Underground Neutrino Experiment is the newest member of the club. This month, the DUNE collaboration surpassed 1000 collaborators from 30 countries.

From its place a mile beneath the earth at the Sanford Underground Research Facility in South Dakota, DUNE will investigate the behavior of neutrinos, which are invisible, nearly massless particles that rarely interact with other matter. The neutrinos will come from Fermilab, 800 miles away.

Neutrino research could help scientists answer the question of why there is an imbalance between matter and antimatter in the universe. Groundbreaking for DUNE occurred on July 21, and the experiment will start taking data in around 2025.

Honorable mentions

A few notable collaborations have made it close to 1000 but didn’t quite make the list. LHCb, the fourth major detector at LHC, boasts a collaboration 800 strong. Over 700 collaborators work on the Belle II experiment at KEK in Japan, which will begin taking data in 2018, studying the properties of B mesons, particles that contain a bottom quark. The 600-member BaBar collaboration at SLAC National Accelerator Laboratory also studies B mesons. STAR, a detector at Brookhaven National Laboratory that probes the conditions of the early universe, has more than 600 collaborators from 55 institutions. The CDF and DZero collaborations at Fermilab, best known for their co-discovery of the top quark in 1995, had about 700 collaborators at their peak.

Expanding the search for dark matter

Tue, 08/22/2017 - 16:13

At a recent meeting, scientists shared ideas for searching for dark matter on the (relative) cheap.

Thirty-one years ago, scientists made their first attempt to find dark matter with a particle detector in a South Dakota mine. 

Since then, researchers have uncovered enough clues to think dark matter makes up approximately 26.8 percent of all the matter and energy in the universe. They think it forms a sort of gravitational scaffolding for the galaxies and galaxy clusters our telescopes do reveal, shaping the structure of our universe while remaining unseen. 

These conclusions are based on indirect evidence such as the behavior of galaxies and galaxy clusters. Direct detection experiments—ones designed to actually sense a dark matter particle pinging off the nucleus of an atom—have yet to find what they’re looking for. Nor has dark matter been seen at the Large Hadron Collider. That invisible, enigmatic material, that Greta Garbo of particle physics, still wants to be alone. 

It could be that researchers are just looking in the wrong place. Much of the search for dark matter has focused on particles called WIMPs, weakly interacting massive particles. But interest in WIMP alternatives has been growing, prompting the development of a variety of small-scale research projects to investigate some of the most promising prospects. 

In March more than 100 scientists met at the University of Maryland for “Cosmic Visions: New Ideas in Dark Matter,” a gathering to take the pulse of the post-WIMP dark matter landscape for the Department of Energy. That pulse was surprisingly strong. Organizers recently published a white paper detailing the results.

The conference came about partly because, “it seemed a good time to get everyone together to see what each experiment was doing, where they reinforced each other and where they did something new,” says Natalia Toro, a theorist at SLAC National Accelerator Laboratory and a member of the Cosmic Visions Scientific Advisory Committee. What she and many other participants didn’t expect, Toro says, was just how many good ideas would be presented. 

Almost 50 experiments in various stages of development were presented during three days of talks, and a similar number of potential experiments were discussed.

Some of the experiments presented would be designed to look for dark matter particles that are lighter than traditional WIMPs, or for the new fundamental forces through which such particles could interact. Others would look for oscillating forces produced by dark matter particles trillions of times lighter than the electron. Still others would look for different dark matter candidates, such as primordial black holes. 

The scientists at the workshop were surprised by how small and relatively inexpensive many of the experiments could be, says Philip Schuster, a particle theorist at SLAC National Accelerator Laboratory.

“‘Small’ and ‘inexpensive’ depend on what technology you’re using, of course,” Schuster says. DOE is prepared to provide funding to the tune of $10 million (still a fraction of the cost of a current WIMP experiment), and many of the experiments could cost in the $1 to $2 million range.

Several factors work together to lessen the cost. For example, advances in detector technology and quantum sensors have made technology cheaper. Then there are small detectors that can be placed at already-existing large facilities like the Heavy Photon Search, a dark-sector search at Jefferson Lab. “It’s basically a table-top detector, as opposed to CMS and ATLAS at the Large Hadron Collider, which took years to build and weigh as much as a battleship,” Schuster says.

Experimentalist Joe Incandela of the University of California, Santa Barbara and one of the coordinators of the Cosmic Visions effort, has a simple explanation for this current explosion of ideas. “There’s a good synergy between the technology and interest in dark matter,” he says. 

Incandela says he is feeling the synergy himself. He is a former spokesperson for CMS, a battleship-class experiment in which he continues to play an active role while also developing the Light Dark Matter Experiment, which would use a high-resolution silicon-based calorimeter that he originally helped develop for CMS to search for an alternative to WIMPs. 

“It occurred to me that this calorimeter technology could very useful for low-mass dark matter searches,” he says. “My hope is that, starting soon, and spanning roughly five years, the funding—and not very much is needed—will be available to support experiments that can cover a lot more of the landscape where dark matter may be hiding. It’s very exciting.”

QuarkNet takes on solar eclipse science

Wed, 08/16/2017 - 19:46

High school students nationwide will study the effects of the solar eclipse on cosmic rays.

While most people are marveling at Monday’s eclipse, a group of researchers will be measuring its effects on cosmic rays—particles from space that reach collide with the earth’s atmosphere to produce muons, heavy cousins of the electron. But these researchers aren’t the usual PhD-holding suspects: They’re still in high school.

More than 25 groups of high school students and teachers nationwide will use small-scale detectors to find out whether the number of cosmic rays raining down on Earth changes during an eclipse. Although the eclipse event will last only three hours, this student experiment has been a months-long collaboration.

The cosmic ray detectors used for this experiment were provided as kits by QuarkNet, an outreach program that gives teachers and students opportunities to try their hands at high-energy physics research. Through QuarkNet, high school classrooms can participate in a whole range of physics activities, such as analyzing real data from the CMS experiment at CERN and creating their own experiments with detectors.

“Really active QuarkNet groups run detectors all year and measure all sorts of things that would sound crazy to a physicist,” says Mark Adams, QuarkNet’s cosmic ray studies coordinator. “It doesn’t really matter what the question is as long as it allows them to do science.”

And this year’s solar eclipse will give students a rare chance to answer a cosmic question: Is the sun a major producer of the cosmic rays that bombard Earth, or do they come from somewhere else?

“We wanted to show that, if the rate of cosmic rays changes a lot during the eclipse, then the sun is a big source of cosmic rays,” Adams says. “We sort of know that the sun is not the main source, but it’s a really neat experiment. As far as we know, no one has ever done this with cosmic ray muons at the surface.”

Adams and QuarkNet teacher Nate Unterman will be leading a group of nine students and five adults to Missouri to the heart of the path of totality—where the moon will completely cover the sun—to take measurements of the event. Some QuarkNet groups will stay put, measuring what effect a partial eclipse might have on cosmic rays.  

Most cosmic rays are likely high-energy particles from exploding stars deep in space, which are picked up via muons in QuarkNet detectors. But the likely result of the experiment—that cosmic rays don’t change their rate when the moon moves in front of the sun—doesn’t eclipse the excitement for the students in the collaboration.

“They’ve been working for months and months to develop the design for the measurements and the detectors,” Adams says. “That’s the great part—they’re not focused on what the answer is but the best way to find it.”

Mark Adams

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