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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

Dark matter hunt with LUX-ZEPLIN

Tue, 08/15/2017 - 18:36

A video from SLAC National Accelerator Laboratory explains how the upcoming LZ experiment will search for the missing 85 percent of the matter in the universe.

What exactly is dark matter, the invisible substance that accounts for 85 percent of all the matter in the universe but can’t be seen even with our most advanced scientific instruments?

Most scientists believe it’s made of ghostly particles that rarely bump into their surroundings. That’s why billions of dark matter particles might zip right through our bodies every second without us even noticing. Leading candidates for dark matter particles are WIMPs, or weakly interacting massive particles.

Scientists at SLAC National Accelerator Laboratory are helping to build and test one of the biggest and most sensitive detectors ever designed to catch a WIMP: the LUX-ZEPLIN or LZ detector. The following video explains how it works.

Dark Matter Hunt with LUX-ZEPLIN (LZ) Video of Dark Matter Hunt with LUX-ZEPLIN (LZ)

Think FAST

Thu, 08/10/2017 - 15:00

The new Fermilab Accelerator Science and Technology facility at Fermilab looks to the future of accelerator science.

Unlike most particle physics facilities, the new Fermilab Accelerator Science and Technology facility (FAST) wasn’t constructed to find new particles or explain basic physical phenomena. Instead, FAST is a kind of workshop—a space for testing novel ideas that can lead to improved accelerator, beamline and laser technologies.

Historically, accelerator research has taken place on machines that were already in use for experiments, making it difficult to try out new ideas. Tinkering with a physicist’s tools mid-search for the secrets of the universe usually isn’t a great idea. By contrast, FAST enables researchers to study pieces of future high-intensity and high-energy accelerator technology with ease.

“FAST is specifically aiming to create flexible machines that are easily reconfigurable and that can be accessed on very short notice,” says Alexander Valishev, head of department that manages FAST. “You can roll in one experiment and roll the other out in a matter of days, maybe months, without expensive construction and operation costs.”

This flexibility is part of what makes FAST a useful place for training up new accelerator scientists. If a student has an idea, or something they want to study, there’s plenty of room for experimentation.

“We want students to come and do their thesis research at FAST, and we already have a number of students working.” Valishev says. “We have already had a PhD awarded on the basis of work done at FAST, but we want more of that.”

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This yellow cyromodule will house the superconducting cavities that take the beam’s energy from 50 to 300 MeV. 

Courtesy of Fermilab Small ring, bright beam

FAST will eventually include three parts: an electron injector, a proton injector and a particle storage ring called the Integrable Optics Test Accelerator, or IOTA. Although it will be small compared to other rings—only 40 meters long, while Fermilab’s Main Injector has a circumference of 3 kilometers—IOTA will be the centerpiece of FAST after its completion in 2019. And it will have a unique feature: the ability to switch from being an electron accelerator to a proton accelerator and back again.

“The sole purpose of this synchrotron is to test accelerator technology and develop that tech to test ideas and theories to improve accelerators everywhere,” says Dan Broemmelsiek, a scientist in the IOTA/FAST department.

One aspect of accelerator technology FAST focuses on is creating higher-intensity or “brighter” particle beams.

Brighter beams pack a bigger particle punch. A high-intensity beam could send a detector twice as many particles as is usually possible. Such an experiment could be completed in half the time, shortening the data collection period by several years.

IOTA will test a new concept for accelerators called integrable optics, which is intended to create a more concentrated, stable beam, possibly producing higher intensity beams than ever before.

“If this IOTA thing works, I think it could be revolutionary,” says Jamie Santucci, an engineering physicist working on FAST. “It’s going to allow all kinds of existing accelerators to pack in way more beam. More beam, more data.”

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The beam starts here: Once electrons are sent down the beamline, they pass through the a set of solenoid magnets—the dark blue rings—before entering the first two superconducting cavities.

Courtesy of Fermilab Maximum energy milestone

Although the completion of IOTA is still a few years away, the electron injector will reach a milestone this summer: producing an electron beam with the energy of 300 million electronvolts (MeV).

The electron injector for IOTA is a research vehicle in its own right,” Valishev says. It provides scientists a chance to test superconducting accelerators, a key piece of technology for future physics machines that can produce intense acceleration at relatively low power.

“At this point, we can measure things about the beam, chop it up or focus it,” Broemmelsiek says. “We can use cameras to do beam diagnostics, and there’s space here in the beamline to put experiments to test novel instrumentation concepts.”

The electron beam’s previous maximum energy of 50 MeV was achieved by passing the beam through two superconducting accelerator cavities and has already provided opportunities for research. The arrival of the 300 MeV beam this summer—achieved by sending the beam through another eight superconducting cavities—will open up new possibilities for accelerator research, with some experiments already planned to start as soon as the beam is online.

Electronics for IOTA

Chip Edstrom FAST forward

The third phase of FAST, once IOTA is complete, will be the construction of the proton injector.

“FAST is unique because we will specifically target creating high-intensity proton beams,” Valishev says.

This high-intensity proton beam research will directly translate to improving research into elusive particles called neutrinos, Fermilab’s current focus.

“In five to 10 years, you’ll be talking to a neutrino guy and they’ll go, ‘I don’t know what the accelerator guys did, but it’s fabulous. We’re getting more neutrinos per hour than we ever thought we would,’” Broemmelsiek says.

Creating new accelerator technology is often an overlooked area in particle physics, but the freedom to try out new ideas and discover how to build better machines for research is inherently rewarding for people who work at FAST.

“Our business is science, and we’re supposed to make science, and we work really hard to do that,” Broemmelsiek says. “But it’s also just plain ol’ fun.”

A new search for dark matter 6800 feet underground

Tue, 08/08/2017 - 15:00

Prototype tests of the future SuperCDMS SNOLAB experiment are in full swing.

When an extraordinarily sensitive dark matter experiment goes online at one of the world’s deepest underground research labs, the chances are better than ever that it’ll find evidence for particles of dark matter—a substance that makes up 85 percent of all matter in the universe but whose constituents have never been detected.

The heart of the experiment, called SuperCDMS SNOLAB, will be one of the most sensitive detectors for hypothetical dark matter particles called WIMPs, short for “weakly interacting massive particles.” SuperCDMS SNOLAB is one of two next-generation experiments (the other one being an experiment called LZ) selected by the US Department of Energy and the National Science Foundation to take the search for WIMPs to the next level, beginning in the early 2020s.

“The experiment will allow us to enter completely unexplored territory,” says Richard Partridge, head of the SuperCDMS SNOLAB group at the Kavli Institute for Particle Astrophysics and Cosmology, a joint institute of Stanford University and SLAC National Accelerator Laboratory. “It’ll be the world’s most sensitive detector for WIMPs with relatively low mass, complementing LZ, which will look for heavier WIMPs.”  

The experiment will operate deep underground at Canadian laboratory SNOLAB inside a nickel mine near the city of Sudbury, where 6800 feet of rock provide a natural shield from high-energy particles from space, called cosmic rays. This radiation would not only cause unwanted background in the detector; it would also create radioactive isotopes in the experiment’s silicon and germanium sensors, making them useless for the WIMP search. That’s also why the experiment will be assembled from major parts at its underground location.

A detector prototype is currently being tested at SLAC, which oversees the efforts of the SuperCDMS SNOLAB project.

Colder than the universe

The only reason we know dark matter exists is that its gravity pulls on regular matter, affecting how galaxies rotate and light propagates. But researchers believe that if WIMPs exist, they could occasionally bump into normal matter, and these collisions could be picked up by modern detectors.

SuperCDMS SNOLAB will use germanium and silicon crystals in the shape of oversized hockey pucks as sensors for these sporadic interactions. If a WIMP hits a germanium or silicon atom inside these crystals, two things will happen: The WIMP will deposit a small amount of energy, causing the crystal lattice to vibrate, and it’ll create pairs of electrons and electron deficiencies that move through the crystal and alter its electrical conductivity. The experiment will measure both responses. 

“Detecting the vibrations is very challenging,” says KIPAC’s Paul Brink, who oversees the detector fabrication at Stanford. “Even the smallest amounts of heat cause lattice vibrations that would make it impossible to detect a WIMP signal. Therefore, we’ll cool the sensors to about one hundredth of a Kelvin, which is much colder than the average temperature of the universe.”

These chilly temperatures give the experiment its name: CDMS stands for “Cryogenic Dark Matter Search.” (The prefix “Super” indicates that the experiment is more sensitive than previous detector generations.)

The use of extremely cold temperatures will be paired with sophisticated electronics, such as transition-edge sensors that switch from a superconducting state of zero electrical resistance to a normal-conducting state when a small amount of energy is deposited in the crystal, as well as superconducting quantum interference devices, or SQUIDs, that measure these tiny changes in resistance.      

The experiment will initially have four detector towers, each holding six crystals. For each crystal material—silicon and germanium—there will be two different detector types, called high-voltage (HV) and interleaved Z-sensitive ionization phonon (iZIP) detectors. Future upgrades can further boost the experiment’s sensitivity by increasing the number of towers to 31, corresponding to a total of 186 sensors.

Four SuperCDMS SNOLAB iZIP detectors at the Stanford Nanofabrication Facility

Matt Cherry

Electrical readout section of SNOLAB Engineering Tower

Paul Brink

Mixing chamber for the dilution fridge manufactured by BlueFors Cryogenics and installed in Building 33 at SLAC

Paul Brink

Dilution fridge

Paul Brink

Mechanical test-fit assembly of SNOLAB Engineering Tower into dilution fridge test facility in Building 33 at SLAC

Paul Brink

SNOLAB Engineering Tower prepared for installation into dilution fridge test facility

Paul Brink

Tsuguo Aramaki completes the assembly of the dilution fridge test facility at SLAC.

Paul Brink

Mike Racine of SLAC inspects the SNOLAB Engineering Tower installed in the dilution fridge test facility.

Chris Smith/SLAC National Accelerator Laboratory

Tsuguo Aramaki of SLAC performs a diagnostic checkout of a SNOLAB Tower installed in the dilution fridge test facility.

Chris Smith/SLAC National Accelerator Laboratory

Diagnostic test chips prepared for installation into the SNOLAB Engineering Tower

Chris Smith/SLAC National Accelerator Laboratory

Mike Racine of SLAC installs the SNOLAB Engineering Tower into the dilution fridge test facility.

Chris Smith/SLAC National Accelerator Laboratory

Tsuguo Aramaki of SLAC builds the detector stack on the SNOLAB Engineering Tower.

Chris Smith/SLAC National Accelerator Laboratory

Paul Brink of SLAC wrangles the SNOLAB Engineering Tower.

Chris Smith/SLAC National Accelerator Laboratory

Mike Racine and Paul Brink of SLAC install the SNOLAB Engineering Tower into the dilution fridge test facility.

Chris Smith/SLAC National Accelerator Laboratory

A display shows the first photons from the SuperCDMS SNOLAB HV detector run in the SLAC dilution fridge test facility.

Paul Brink

SNOLAB Engineering Tower assembled by Tsuguo Aramaki (SLAC) and Xuji Zhao (Texas A&M)

Paul Brink

Tsuguo Aramaki (SLAC), Caleb Fink (UCB), Sam Watkins (UCB) and Matt Pyle (UCB)

Paul Brink

SNOLAB iZIP detector fabricated at Texas A&M university and packaged by SLAC's Matt Cherry for testing at UMN Minneapolis

Matt Cherry

SNOLAB prototype HV detector fabricated and packaged by Matt Cherry (SLAC) in SNOLAB prototype hardware

Matt Cherry

High-density Vacuum Interface Board developed at Fermilab for readout of cryogenic detectors

Paul Brink

A SNOLAB Engineering Tower is installed in the dilution fridge to test cryogenic flex-cable readout configurations.

Paul Brink Previous Next Working hand in hand

The work under way at SLAC serves as a system test for the future SuperCDMS SNOLAB experiment. Researchers are testing the four different detector types, the way they are integrated into towers, their superconducting electrical connectors and the refrigerator unit that cools them down to a temperature of almost absolute zero.

“These tests are absolutely crucial to verify the design of these new detectors before they are integrated in the experiment underground at SNOLAB,” says Ken Fouts, project manager for SuperCDMS SNOLAB at SLAC. “They will prepare us for a critical DOE review next year, which will determine whether the project can move forward as planned.” DOE is expected to cover about half of the project costs, with the other half coming from NSF and a contribution from the Canadian Foundation for Innovation. 

Important work is progressing at all partner labs of the SuperCDMS SNOLAB project. Fermi National Accelerator Laboratory is responsible for the cryogenics infrastructure and the detector shielding—both will enable searching for faint WIMP signals in an environment dominated by much stronger unwanted background signals. Pacific Northwest National Laboratory will lend its expertise in understanding background noise in highly sensitive precision experiments. A number of US universities are involved in various aspects of the project, including detector fabrication, tests, data analysis and simulation.

The project also benefits from international partnerships with institutions in Canada, France, the UK and India. The Canadian partners are leading the development of the experiment’s data acquisition and will provide the infrastructure at SNOLAB. 

“Strong partnerships create a lot of synergy and make sure that we’ll get the best scientific value out of the project,” says Fermilab’s Dan Bauer, spokesperson of the SuperCDMS collaboration, which consists of 109 scientists from 22 institutions, including numerous universities. “Universities have lots of creative students and principal investigators, and their talents are combined with the expertise of scientists and engineers at the national labs, who are used to successfully manage and build large projects.”

SuperCDMS SNOLAB will be the fourth generation of experiments, following CDMS-I at Stanford, CDMS-II at the Soudan mine in Minnesota, and a first version of SuperCDMS at Soudan, which completed operations in 2015.   

“Over the past 20 years we’ve been pushing the limits of our detectors to make them more and more sensitive for our search for dark matter particles,” says KIPAC’s Blas Cabrera, project director of SuperCDMS SNOLAB. “Understanding what constitutes dark matter is as fundamental and important today as it was when we started, because without dark matter none of the known structures in the universe would exist—no galaxies, no solar systems, no planets and no life itself.”

Our clumpy cosmos

Thu, 08/03/2017 - 16:37

The Dark Energy Survey reveals the most accurate measurement of dark matter structure in the universe.

Imagine planting a single seed and, with great precision, being able to predict the exact height of the tree that grows from it. Now imagine traveling to the future and snapping photographic proof that you were right.

If you think of the seed as the early universe, and the tree as the universe the way it looks now, you have an idea of what the Dark Energy Survey (DES) collaboration has just done. In a presentation today at the American Physical Society Division of Particles and Fields meeting at the US Department of Energy’s (DOE) Fermi National Accelerator Laboratory, DES scientists will unveil the most accurate measurement ever made of the present large-scale structure of the universe.

These measurements of the amount and “clumpiness” (or distribution) of dark matter in the present-day cosmos were made with a precision that, for the first time, rivals that of inferences from the early universe by the European Space Agency’s orbiting Planck observatory. The new DES result (the tree, in the above metaphor) is close to “forecasts” made from the Planck measurements of the distant past (the seed), allowing scientists to understand more about the ways the universe has evolved over 14 billion years.

“This result is beyond exciting,” says Scott Dodelson of Fermilab, one of the lead scientists on this result. “For the first time, we’re able to see the current structure of the universe with the same clarity that we can see its infancy, and we can follow the threads from one to the other, confirming many predictions along the way.”

Most notably, this result supports the theory that 26 percent of the universe is in the form of mysterious dark matter and that space is filled with an also-unseen dark energy, which is causing the accelerating expansion of the universe and makes up 70 percent.

Paradoxically, it is easier to measure the large-scale clumpiness of the universe in the distant past than it is to measure it today. In the first 400,000 years following the Big Bang, the universe was filled with a glowing gas, the light from which survives to this day. Planck’s map of this cosmic microwave background radiation gives us a snapshot of the universe at that very early time. Since then, the gravity of dark matter has pulled mass together and made the universe clumpier over time. But dark energy has been fighting back, pushing matter apart. Using the Planck map as a start, cosmologists can calculate precisely how this battle plays out over 14 billion years.

“The DES measurements, when compared with the Planck map, support the simplest version of the dark matter/dark energy theory,” says Joe Zuntz, of the University of Edinburgh, who worked on the analysis. “The moment we realized that our measurement matched the Planck result within 7 percent was thrilling for the entire collaboration.”

This map of dark matter is made from gravitational lensing measurements of 26 million galaxies in the Dark Energy Survey. The map covers about 1/30th of the entire sky and spans several billion light-years in extent. Red regions have more dark matter than average, blue regions less dark matter.

Chihway Chang of the Kavli Institute for Cosmological Physics at the University of Chicago and the DES collaboration.

The primary instrument for DES is the 570-megapixel Dark Energy Camera, one of the most powerful in existence, able to capture digital images of light from galaxies eight billion light-years from Earth. The camera was built and tested at Fermilab, the lead laboratory on the Dark Energy Survey, and is mounted on the National Science Foundation’s 4-meter Blanco telescope, part of the Cerro Tololo Inter-American Observatory in Chile, a division of the National Optical Astronomy Observatory. The DES data are processed at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign.

Scientists on DES are using the camera to map an eighth of the sky in unprecedented detail over five years. The fifth year of observation will begin in August. The new results released today draw from data collected only during the survey’s first year, which covers 1/30th of the sky.

“It is amazing that the team has managed to achieve such precision from only the first year of their survey,” says National Science Foundation Program Director Nigel Sharp. “Now that their analysis techniques are developed and tested, we look forward with eager anticipation to breakthrough results as the survey continues.”

DES scientists used two methods to measure dark matter. First, they created maps of galaxy positions as tracers, and second, they precisely measured the shapes of 26 million galaxies to directly map the patterns of dark matter over billions of light-years using a technique called gravitational lensing.

To make these ultra-precise measurements, the DES team developed new ways to detect the tiny lensing distortions of galaxy images, an effect not even visible to the eye, enabling revolutionary advances in understanding these cosmic signals. In the process, they created the largest guide to spotting dark matter in the cosmos ever drawn (see image). The new dark matter map is 10 times the size of the one DES released in 2015 and will eventually be three times larger than it is now.

“It’s an enormous team effort and the culmination of years of focused work,” says Erin Sheldon, a physicist at the DOE’s Brookhaven National Laboratory, who co-developed the new method for detecting lensing distortions.

These results and others from the first year of the Dark Energy Survey will be released today online and announced during a talk by Daniel Gruen, NASA Einstein fellow at the Kavli Institute for Particle Astrophysics and Cosmology at DOE’s SLAC National Accelerator Laboratory, at 5 pm Central time. The talk is part of the APS Division of Particles and Fields meeting at Fermilab and will be streamed live.

The results will also be presented by Kavli fellow Elisabeth Krause of the Kavli Insitute for Particle Astrophysics and Cosmology at SLAC at the TeV Particle Astrophysics Conference in Columbus, Ohio, on Aug. 9; and by Michael Troxel, postdoctoral fellow at the Center for Cosmology and AstroParticle Physics at Ohio State University, at the International Symposium on Lepton Photon Interactions at High Energies in Guanzhou, China, on Aug. 10. All three of these speakers are coordinators of DES science working groups and made key contributions to the analysis.

“The Dark Energy Survey has already delivered some remarkable discoveries and measurements, and they have barely scratched the surface of their data,” says Fermilab Director Nigel Lockyer. “Today’s world-leading results point forward to the great strides DES will make toward understanding dark energy in the coming years.”

A version of this article was published by Fermilab.

Tuning in for science

Tue, 08/01/2017 - 15:50

The sprawling Square Kilometer Array radio telescope hunts signals from one of the quietest places on earth.

When you think of radios, you probably think of noise. But the primary requirement for building the world’s largest radio telescope is keeping things almost perfectly quiet.

Radio signals are constantly streaming to Earth from a variety of sources in outer space. Radio telescopes are powerful instruments that can peer into the cosmos—through clouds and dust—to identify those signals, picking them up like a signal from a radio station. To do it, they need to be relatively free from interference emitted by cell phones, TVs, radios and their kin.

That’s one reason the Square Kilometer Array is under construction in the Great Karoo, 400,000 square kilometers of arid, sparsely populated South African plain, along with a component in the Outback of Western Australia. The Great Karoo is also a prime location because of its high altitude—radio waves can be absorbed by atmospheric moisture at lower altitudes. SKA currently covers some 1320 square kilometers of the landscape.

Even in the Great Karoo, scientists need careful filtering of environmental noise. Effects from different levels of radio frequency interference (RFI) can range from “blinding” to actually damaging the instruments. Through South Africa’s Astronomy Geographic Advantage Act, SKA is working toward “radio protection,” which would dedicate segments of the bandwidth for radio astronomy while accommodating other private and commercial RF service requirements in the region.

“Interference affects observational data and makes it hard and expensive to remove or filter out the introduced noise,” says Bernard Duah Asabere, Chief Scientist of the Ghana team of the African Very Long Baseline Interferometry Network (African VLBI Network, or AVN), one of the SKA collaboration groups in eight other African nations participating in the project.

SKA “will tackle some of the fundamental questions of our time, ranging from the birth of the universe to the origins of life,” says SKA Director-General Philip Diamond. Among the targets: dark energy, Einstein’s theory of gravity and gravitational waves, and the prevalence of the molecular building blocks of life across the cosmos.

SKA-South Africa can detect radio spectrum frequencies from 350 megahertz to 14 gigahertz. Its partner Australian component will observe the lower-frequency scale, from 50 to 350 megahertz. Visible light, for comparison, has frequencies ranging from 400 to 800 million megahertz. SKA scientists will process radiofrequency waves to form a picture of their source.

A precursor instrument to SKA called MeerKAT (named for the squirrel-sized critters indigenous to the area), is under construction in the Karoo. This array of 16 dishes in South Africa achieved first light on June 19, 2016. MeerKAT focused on 0.01 percent of the sky for 7.5 hours and saw 1300 galaxies—nearly double the number previously known in that segment of the cosmos. 

Since then, MeerKAT met another milestone with 32 integrated antennas. MeerKat will also reach its full array of 64 dishes early next year, making it one of the world’s premier radio telescopes. MeerKAT will eventually be integrated into SKA Phase 1, where an additional 133 dishes will be built. That will bring the total number of antennas for SKA Phase I in South Africa to 197 by 2023. So far, 32 dishes are fully integrated and are being commissioned for science operations.

On completion of SKA 2 by 2030, the detection area of the receiver dishes will exceed 1 square kilometer, or about 11,000 square feet. Its huge size will make it 50 times more sensitive than any other radio telescope. It is expected to operate for 50 years.

SKA is managed by a 10-nation consortium, including the UK, China, India and Australia as well as South Africa, and receives support from another 10 countries, including the US. The project is headquartered at Jodrell Bank Observatory in the UK.

The full SKA will use radio dishes across Africa and Australia, and collaboration members say it will have a farther reach and more detailed images than any existing radio telescope.

In preparation for the SKA, South Africa and its partner countries developed AVN to establish a network of radiotelescopes across the African continent. One of its projects is the refurbishing of redundant 30-meter-class antennas, or building new ones across the partner countries, to operate as networked radio telescopes.

The first project of its kind is the AVN Ghana project, where an idle 32-meter diameter dish has been refurbished and revamped with a dual receiver system at 5 and 6.7 gigahertz central frequencies for use as a radio telescope. The dish was previously owned and operated by the government and the company Vodafone Ghana as a telecommunications facility. Now it will explore celestial objects such as extragalactic nebulae, pulsars and other RF sources in space, such as molecular clouds, called masers.

Asabere’s group will be able to tap into areas of SKA’s enormous database (several supercomputers’ worth) over the Internet. So will groups in Botswana, Kenya, Madagascar, Mauritius, Mozambique, Namibia and Zambia. SKA is also offering extensive outreach in participating countries and has already awarded 931 scholarships, fellowships and grants.

Other efforts in Ghana include introducing astronomy in the school curricula, training students in astronomy and related technologies, doing outreach in schools and universities, receiving visiting students at the telescope site and hosting programs such as the West African International Summer School for Young Astronomers taking place this week.

Asabere, who achieved his advanced degrees in Sweden (Chalmers University of Technology) and South Africa (University of Johannesburg), would like to see more students trained in Ghana, and would like get more researchers on board. He also hopes for the construction of the needed infrastructure, more local and foreign partnerships and strong governmental backing.

“I would like the opportunity to practice my profession on my own soil,” he says.

That day might not be far beyond the horizon. The Leverhulme-Royal Society Trust and Newton Fund in the UK are co-funding extensive human capital development programs in the SKA-AVN partner countries. A seven-member Ghanaian team, for example, has undergone training in South Africa and has been instructed in all aspects of the project, including the operation of the telescope. 

Several PhD students and one MSc student from Ghana have received SKA-SA grants to pursue further education in astronomy and engineering. The Royal Society has awarded funding in collaboration with Leeds University to train two PhDs and 60 young aspiring scientists in the field of astrophysics.

Based on the success of the Leverhulme-Royal Society program, a joint UK-South Africa Newton Fund intervention (DARA—the Development in Africa with Radio Astronomy) has since been initiated in other partner countries to grow high technology skills that could lead to broader economic development in Africa. 

As SKA seeks answers to complex questions over the next five decades, there should be plenty of opportunities for science throughout the Southern Hemisphere. Though it lives in one of the quietest places, SKA hopes to be heard loud and clear.

An underground groundbreaking

Mon, 07/31/2017 - 21:35

A physics project kicks off construction a mile underground.

For many government officials, groundbreaking ceremonies are probably old hat—or old hardhat. But how many can say they’ve been to a groundbreaking that’s nearly a mile underground?

A group of dignitaries, including a governor and four members of Congress, now have those bragging rights. On July 21, they joined scientists and engineers 4850 feet beneath the surface at the Sanford Underground Research Facility to break ground on the Long-Baseline Neutrino Facility (LBNF).

LBNF will house massive, four-story-high detectors for the Deep Underground Neutrino Experiment (DUNE) to learn more about neutrinos—invisible, almost massless particles that may hold the key to how the universe works and why matter exists.  Fourteen shovels full of dirt marked the beginning of construction for a project that could be, well, groundbreaking.

The Sanford Underground Research Facility in Lead, South Dakota resides in what was once the deepest gold mine in North America, which has been repurposed as a place for discovery of a different kind.

“A hundred years ago, we mined gold out of this hole in the ground. Now we’re going to mine knowledge,” said US Representative Kristi Noem of South Dakota in an address at the groundbreaking.

Transforming an old mine into a lab is more than just a creative way to reuse space. On the surface, cosmic rays from the sun constantly bombard us, causing cosmic noise in the sensitive detectors scientists use to look for rare particle interactions. But underground, shielded by nearly a mile of rock, there’s cosmic quiet. Cosmic rays are rare, making it easier for scientists to see what’s going on in their detectors without being clouded by interference.

Going down?

It may be easier to analyze data collected underground, but entering the subterranean science facility can be a chore. Nearly 60 people took a trip underground to the groundbreaking site, requiring some careful elevator choreography.

Before venturing into the deep below, reporters and representatives alike donned safety glasses, hardhats and wearable flashlights. They received two brass tags engraved with their names—one to keep and another to hang on a corkboard—a process called “brassing in.” This helps keep track of who’s underground in case of emergency.

The first group piled into the open-top elevator, known as a cage, to begin the descent. As the cage glides through a mile of mountain, it’s easy to imagine what it must have been like to be a miner back when Sanford Lab was the Homestake Mine. What’s waiting below may have changed, but the method of getting there hasn’t: The winch lowering the cage at 500-feet-a-minute is 80 years old and still works perfectly.

The ride to the 4850-level takes about 10 minutes in the cramped cage—it fits 35, but even with 20 people it feels tight. Water drips in through the ceiling as the open elevator chugs along, occasionally passing open mouths in the rock face of drifts once mined for gold.

 “When you go underground, you start to think ‘It has never rained in here. And there’s never been daylight,’” says Tim Meyer, Chief Operating Officer of Fermilab, who attended the groundbreaking. “When you start thinking about being a mile below the surface, it just seems weird, like you’re walking through a piece of Swiss cheese.”

Where the cage stops at the 4850-level would be the destination of most elevator occupants on a normal day, since the shaft ends near the entrance of clean research areas housing Sanford Lab experiments. But for the contingent traveling to the future site of LBNF/DUNE on the other end of the mine, the journey continued, this time in an open-car train. It’s almost like a theme-park ride as the motor (as it’s usually called by Sanford staff) clips along through a tunnel, but fortunately, no drops or loop-the-loops are involved.

“The same rails now used to transport visitors and scientists were once used by the Homestake miners to remove gold from the underground facility,” says Jim Siegrist, Associate Director of High Energy Physics at the Department of Energy. “During the ride, rock bolts and protective screens attached to the walls were visible by the light of the headlamp mounted on our hardhats.”

After a 15-minute ride, the motor reached its destination and it was business as usual for a groundbreaking ceremony: speeches, shovels and smiling for photos. A fresh coat of white paint (more than 100 gallons worth) covered the wall behind the officials, creating a scene that almost could have been on the surface.

“Celebrating the moment nearly a mile underground brought home the enormity of the task and the dedication required for such precise experiments,” says South Dakota Governor Dennis Daugaard. “I know construction will take some time, but it will be well worth the wait for the Sanford Underground Research Facility to play such a vital role in one of the most significant physics experiments of our time."

What’s the big deal?

The process to reach the groundbreaking site is much more arduous than reaching most symbolic ceremonies, so what would possess two senators, two representatives, a White House representative, a governor and delegates from three international science institutions (to mention a few of the VIPs) to make the trip? Only the beginning of something huge—literally.

“This milestone represents the start of construction of the largest mega-science project in the United States,” said Mike Headley, executive director of Sanford Lab.  

The 14 shovelers at the groundbreaking made the first tiny dent in the excavation site for LBNF, which will require the extraction of more than 870,000 tons of rock to create huge caverns for the DUNE detectors. These detectors will catch neutrinos sent 800 miles through the earth from Fermi National Accelerator Laboratory in the hopes that they will tell us something more about these strange particles and the universe we live in.

“We have the opportunity to see truly world-changing discovery,” said US Representative Randy Hultgren of Illinois. “This is unique—this is the picture of incredible discovery and experimentation going into the future.”

Angela Fava: studying neutrinos around the globe

Wed, 07/26/2017 - 18:09

This experimental physicist has followed the ICARUS neutrino detector from Gran Sasso to Geneva to Chicago.

Physicist Angela Fava has been at the enormous ICARUS detector’s side for over a decade. As an undergraduate student in Italy in 2006, she worked on basic hardware for the neutrino hunting experiment: tightening bolts and screws, connecting and reconnecting cables, learning how the detector worked inside and out.

ICARUS (short for Imaging Cosmic And Rare Underground Signals) first began operating for research in 2010, studying a beam of neutrinos created at European laboratory CERN and launched straight through the earth hundreds of miles to the detector’s underground home at INFN Gran Sasso National Laboratory.

In 2014, the detector moved to CERN for refurbishing, and Fava relocated with it. In June ICARUS began a journey across the ocean to the US Department of Energy’s Fermi National Accelerator Laboratory to take part in a new neutrino experiment. When it arrives today, Fava will be waiting.

Fava will go through the installation process she helped with as a student, this time as an expert.

Journey to ICARUS

As a child growing up between Venice and the Alps, Fava always thought she would pursue a career in math. But during a one-week summer workshop before her final year of high school in 2000, she was drawn to experimental physics.

At the workshop, she realized she had more in common with physicists. Around the same time, she read about new discoveries related to neutral, rarely interacting particles called neutrinos. Scientists had recently been surprised to find that the extremely light particles actually had mass and that different types of neutrinos could change into one another. And there was still much more to learn about the ghostlike particles.

At the start of college in 2001, Fava immediately joined the University of Padua neutrino group. For her undergraduate thesis research, she focused on the production of hadrons, making measurements essential to studying the production of neutrinos. In 2004, her research advisor Alberto Guglielmi and his group joined the ICARUS collaboration, and she’s been a part of it ever since.

Fava jests that the relationship actually started much earlier: “ICARUS was proposed for the first time in 1983, which is the year I was born. So we are linked from birth.”

Fava remained at the University of Padua in the same research group for her graduate work. During those years, she spent about half of her time at the ICARUS detector, helping bring it to life at Gran Sasso.

Once all the bolts were tightened and the cables were attached, ICARUS scientists began to pursue their goal of using the detector to study how neutrinos change from one type to another.

During operation, Fava switched gears to create databases to store and log the data. She wrote code to automate the data acquisition system and triggering, which differentiates between neutrino events and background such as passing cosmic rays. “I was trying to take part in whatever activity was going on just to learn as much as possible,” she says.

That flexibility is a trait that Claudio Silverio Montanari, the technical director of ICARUS, praises. “She has a very good capability to adapt,” he says. “Our job, as physicists, is putting together the pieces and making the detector work.”

Changing it up

Adapting to changing circumstances is a skill both Fava and ICARUS have in common. When scientists proposed giving the detector an update at CERN and then using it in a suite of neutrino experiments at Fermilab, Fava volunteered to come along for the ride.

Once installed and operating at Fermilab, ICARUS will be used to study neutrinos from a source a few hundred meters away from the detector. In its new iteration, ICARUS will search for sterile neutrinos, a hypothetical kind of neutrino that would interact even more rarely than standard neutrinos. While hints of these low-mass particles have cropped up in some experiments, they have not yet been detected.

At Fermilab, ICARUS also won’t be buried below more than half a mile of rock, a feature of the INFN setup that shielded it from cosmic radiation from space. That means the triggering system will play an even bigger role in this new experiment, Fava says.

“We have a great challenge ahead of us.” She’s up to the task.

Turning plots into stained glass

Tue, 07/25/2017 - 15:00

Hubert van Hecke, a heavy-ion physicist, transforms particle physics plots into works of art.

At first glance, particle physicist Hubert van Hecke’s stained glass windows simply look like unique pieces of art. But there is much more to them than pretty shapes and colors. A closer look reveals that his creations are actually renditions of plots from particle physics experiments.  

Van Hecke learned how to create stained glass during his undergraduate years at Louisiana State University. “I had an artistic background—my father was a painter, so I thought, if I need a humanities credit, I'll just sign up for this,” van Hecke recalls. “So in order to get my physics’ bachelors, I took stained glass.” 

Over the course of two semesters, van Hecke learned how to cut pieces of glass from larger sheets, puzzle them together, then solder and caulk the joints. “There were various assignments that gave you an enormous amount of elbow room,” he says. “One of them was to do something with Fibonacci numbers, and one was pick your favorite philosopher and made a window related to their work.” 

Van Hecke continued to create windows and mirrors throughout graduate school but stopped for many years while working as a full-time heavy-ion physicist at Los Alamos National Laboratory and raising a family. Only recently did he return to his studio—this time, to create pieces inspired by physics. 

“I had been thinking about designs for a long time—then it struck me that occasionally, you see plots that are interesting, beautiful shapes,” van Hecke says. “So I started collecting pictures as I saw them.”

Hubert van Hecke Hubert van Hecke, Stained glass inspired by the Higgs boson Hubert van Hecke, Stained glass piece inspired by Neutrinos and the MiniBoone in red, orange, and yellow Hubert van Hecke, Stained glass piece inspired by Quarks and Gluons in red and blue Hubert van Hecke, Stained glass 'and Man Created the Universe' Hubert van Hecke, Circular stained glass piece in light and dark blue Hubert van Hecke, Curved lines stained glass piece in red, yellow, and black Hubert van Hecke, Square stained glass piece in red, yellow, green, and blue Previous Next

His first plot-based window, a rectangle-shaped piece with red, orange and yellow glass, was inspired by the results of a neutrino flavor oscillation study from the MiniBooNE experiment at Fermi National Accelerator Laboratory. He created two pieces after that, one from a plot generated during the hunt for the Higgs boson at the Tevatron, also at Fermilab and the other based on an experiment with quarks and gluons. 

According to van Hecke, what inspires him about these plots is “purely the shapes.” 

“In terms of the physics, it's what I run across—for example, I see talks about heavy ion physics, elementary particle physics, and neutrinos, [but] I haven't really gone out and searched in other fields,” he says. “Maybe there are nice plots in biology or astronomy.”

Although van Hecke has not yet displayed his pieces publicly, if he does one day, he plans to include explanations for the phenomena the plots illustrate, such as neutrinos and the Standard Model, as a unique way to communicate science. 

But before that, van Hecke plans to create more stained glass windows. As of two months ago, he is semiretired—and in between runs to Fermilab, where he is helping with the effort to use Argonne National Laboratory's SeaQuest experiment to search for dark photons, he hopes to spend more time in the studio creating the pieces left on the drawing board, which include plots found in experiments investigating the Standard Model, neutrinoless double decay and dark matter interactions. 

“I hope to make a dozen or more,” he says. “As I bump into plots, I'll collect them and hopefully, turn them all into windows.” 

Hubert van Hecke Hubert van Hecke, From the 2016 APS wall calendar, from Phys Rev D91, 07007 (2015) Hubert van Hecke, From the Dark Interactions workshop, talk by Tim M.P. Tait. Annotated version v1 Hubert van Hecke, Dark photons, wwnd 2015 Dipali Sharma Hubert van Hecke Hubert van Hecke, Neutrinoless double beta decay Hubert van Hecke, Neutrino/wimp talk, slide 21 Hubert van Hecke, Neutrinoless double beta decay Hubert van Hecke, ICHEP 2012, Joao Guimaraes da Costa, Harvard Hubert van Hecke, ICHEP 2012, Joao Guimaraes da Costa, Harvard. Hubert van Hecke, Brazil plot from WWND 2015 Dipali Sharma Previous Next

Watch the underground groundbreaking

Fri, 07/21/2017 - 15:00

This afternoon, watch a livestream of the start of excavation for the future home of the Deep Underground Neutrino Experiment.

Today in South Dakota, dignitaries, scientists and engineers will mark the start of construction of the future home of America's flagship neutrino experiment with a groundbreaking ceremony.

Participants will hold shovels and give speeches. But this will be no ordinary groundbreaking. It will take place a mile under the earth at Sanford Underground Research Facility, the deepest underground physics lab in the United States.

The groundbreaking will celebrate the beginning of excavation for the Long-Baseline Neutrino Facility, which will house the Deep Underground Neutrino Experiment. When complete, LBNF/DUNE will be the largest experiment ever built in the US to study the properties of mysterious particles called neutrinos. Unlocking the mysteries of these particles could help explain more about how the universe works and why matter exists at all.

Watch the underground groundbreaking at 2:20 p.m. Mountain Time (3:20 p.m. Central) via livestream.

Shaking the dark matter paradigm

Tue, 07/18/2017 - 15:00

A new theory about gravity challenges our understanding of the universe.

For millennia, humans held a beautiful belief. Our planet, Earth, was at the center of a vast universe, and all of the planets and stars and celestial bodies revolved around us. This geocentric model, though it had floated around since 6th century BCE, was written in its most elegant form by Claudius Ptolemy in 140 AD.

When this model encountered problems, such as the retrograde motions of planets, scientists reworked the data to fit the model by coming up with phenomena such as epicycles, mini orbits.

It wasn’t until 1543, 1400 years later, that Nicolaus Copernicus set in motion a paradigm shift that would give way to centuries of new discoveries. According to Copernicus’ radical theory, Earth was not the center of the universe but simply one of a long line of planets orbiting around the sun.

But even as evidence that we lived in a heliocentric system piled up and scientists such as Galileo Galilei perfected the model, society held onto the belief that the entire universe orbited around Earth until the early 19th century.

To Erik Verlinde, a theoretical physicist at the University of Amsterdam, the idea of dark matter is the geocentric model of the 21st century. 

“What people are doing now is allowing themselves free parameters to sort of fit the data,” Verlinde says. “You end up with a theory that has so many free parameters it's hard to disprove.”

Dark matter, an as-yet-undetected form of matter that scientists believe makes up more than a quarter of the mass and energy of the universe, was first theorized when scientists noticed that stars at the outer edges of galaxies and galaxy clusters were moving much faster than Newton’s theory of gravity said they should. Up until this point, scientists have assumed that the best explanation for this is that there must be missing mass in the universe holding those fast-moving stars in place in the form of dark matter. 

But Verlinde has come up with a set of equations that explains these galactic rotation curves by viewing gravity as an emergent force — a result of the quantum structure of space.

The idea is related to dark energy, which scientists think is the cause for the accelerating expansion of our universe. Verlinde thinks that what we see as dark matter is actually just interactions between galaxies and the sea of dark energy in which they’re embedded.

“Before I started working on this I never had any doubts about dark matter,” Verlinde says. “But then I started thinking about this link with quantum information and I had the idea that dark energy is carrying more of the dynamics of reality than we realize.”

Verlinde is not the first theorist to come up with an alternative to dark matter. Many feel that his theory echoes the sentiment of physicist Mordehai Milgrom’s equations of “modified Newtonian dynamics,” or MOND. Just as Einstein modified Newton’s laws of gravity to fit to the scale of planets and solar systems, MOND modifies Einstein’s laws of gravity to fit to the scale of galaxies and galaxy clusters.

Verlinde, however, makes the distinction that he’s not deriving the equations of MOND, rather he’s deriving what he calls a “scaling relation,” or a volume effect of space-time that only becomes important at large distances. 

Stacy McGaugh, an astrophysicist at Case Western Reserve University, says that while MOND is primarily the notion that the effective force of gravity changes with acceleration, Verlinde’s ideas are more of a ground-up theoretical work.

“He's trying to look at the structure of space-time and see if what we call gravity is a property that emerges from that quantum structure, hence the name emergent gravity,” McGaugh says. “In principle, it's a very different approach that doesn't necessarily know about MOND or have anything to do with it.”

One of the appealing things about Verlinde’s theory, McGaugh says, is that it naturally produces evidence of MOND in a way that “just happens.” 

“That's the sort of thing that one looks for,” McGaugh says. “There needs to be some basis of why MOND happens, and this theory might provide it.”

Verlinde’s ideas have been greeted with a fair amount of skepticism in the scientific community, in part because, according to Kathryn Zurek, a theoretical physicist at the US Department of Energy’s Lawrence Berkeley National Laboratory, his theory leaves a lot unexplained. 

“Theories of modified gravity only attempt to explain galactic rotation curves [those fast-moving planets],” Zurek says. “As evidence for dark matter, that's only one very small part of the puzzle. Dark matter explains a whole host of observations from the time of the cosmic microwave background when the universe was just a few hundred thousand years old through structure formation all the way until today.”


Illustration by Ana Kova

Zurek says that in order for scientists to start lending weight to his claims, Verlinde needs to build the case around his theory and show that it accommodates a wider range of observations. But, she says, this doesn’t mean that his ideas should be written off.

“One should always poke at the paradigm,” Zurek says, “even though the cold dark matter paradigm has been hugely successful, you always want to check your assumptions and make sure that you're not missing something that could be the tip of the iceberg.”

McGaugh had a similar crisis of faith in dark matter when he was working on an experiment wherein MOND’s predictions were the only ones that came true in his data. He had been making observations of low-surface-brightness galaxies, wherein stars are spread more thinly than galaxies such as the Milky Way where the stars are crowded relatively close together.

McGaugh says his results did not make sense to him in the standard dark matter context, and it turned out that the properties that were confusing to him had already been predicted by Milgrom’s MOND equations in 1983, before people had even begun to take seriously the idea of low-surface-brightness galaxies.

Although McGaugh’s experience caused him to question the existence of dark matter and instead argue for MOND, others have not been so quick to join the cause.

“We subscribe to a particular paradigm and most of our thinking is constrained within the boundaries of that paradigm, and so if we encounter a situation in which there is a need for a paradigm shift, it's really hard to think outside that box,” McGaugh says. “Even though we have rules for the game as to when you're supposed to change your mind and we all in principle try to follow that, in practice there are some changes of mind that are so big that we just can't overcome our human nature.”

McGaugh says that many of his colleagues believe that there’s so much evidence for dark matter that it’s a waste of time to consider any alternatives. But he believes that all of the evidence for dark matter might instead be an indication that there is something wrong with our theories of gravity. 

“I kind of worry that we are headed into another thousand years of dark epicycles,” McGaugh says.

But according to Zurek, if MOND came up with anywhere near the evidence that has been amassed for the dark matter paradigm, people would be flocking to it. The problem, she says, is that at the moment MOND just does not come anywhere near to passing the number of tests that cold dark matter has. She adds that there are some physicists who argue that the cold dark matter paradigm can, in fact, explain those observations about low-surface-brightness galaxies.

Recently, Case Western held a workshop wherein they gathered together representatives from different communities, including those working on dark matter models, to discuss dwarf galaxies and the external field effect, which is the notion that very low-density objects will be affected by what’s around them. MOND predicts that the dynamics of a small satellite galaxy will depend on its proximity to its giant host in a way that doesn't happen with dark matter.

McGaugh says that in attendance at the workshop were a group of more philosophically inclined people who use a set of rules to judge theories, which they’ve put together by looking back at how theories have developed in the past. 

“One of the interesting things that came out of that was that MOND is doing better on that score card,” he says. “It’s more progressive in the sense that it's making successful predictions for new phenomena whereas in the case of dark matter we've had to repeatedly invoke ad hoc fixes to patch things up.”

Verlinde’s ideas, however, didn’t come up much within the workshop. While McGaugh says that the two theories are closely enough related that he would hope the same people pursuing MOND would be interested in Verlinde’s theory, he added that not everyone shares that attitude. Many are waiting for more theoretical development and further observational tests.

“The theory needs to make a clear prediction so that we can then devise a program to go out and test it,” he says. “It needs to be further worked out to get beyond where we are now.”

Verlinde says he realizes that he still needs to develop his ideas further and extend them to explain things such as the formation of galaxies and galaxy clusters. Although he has mostly been working on this theory on his own, he recognizes the importance of building a community around his ideas.

Over the past few months, he has been giving presentations at different universities, including Princeton, Harvard, Berkeley, Stanford, and Caltech. There is currently a large community of people working on ideas of quantum information and gravity, he says, and his main goal is to get more people, in particular string theorists, to start thinking about his ideas to help him improve them.

“I think that when we understand gravity better and we use those equations to describe the evolution of the universe, we may be able to answer questions more precisely about how the universe started,” Verlinde says. “I really think that the current description is only part of the story and there's a much deeper way of understanding it—maybe an even more beautiful way.”


SLAC accelerator plans appear in Smithsonian art exhibit

Thu, 07/13/2017 - 15:00

The late artist June Schwarcz found inspiration in some unusual wrapping paper her husband brought home from the lab.


Leroy Schwarcz, one of the first engineers hired to build SLAC National Accelerator Laboratory’s original 2-mile-long linear accelerator, thought his wife might like to use old mechanical drawings of the project as wrapping paper. So, he brought them home.

His wife, acclaimed enamelist June Schwarcz, had other ideas.

Today, works called SLAC Drawing III, VII and VIII, created in 1974 and 1975 from electroplated copper and enamel, form a unique part of a retrospective at the Smithsonian’s Renwick Gallery in Washington, D.C.

Among the richly formed and boldly textured and colored vessels that make up the majority of June’s oeuvre, the SLAC-inspired panels stand out for their fidelity to the mechanical design of their inspiration. 

The description next to the display at the gallery describe the “SLAC Blueprints” as resembling “ancient pictographs drawn on walls of a cave or glyphs carved in stone.” The designs appear to depict accelerator components, such as electromagnets and radio frequency structures.

According to Harold B. Nelson, who curated the exhibit with Bernard N. Jazzar, “The panels are quite unusual in the subtle color palette she chose; in her use of predominantly opaque enamels; in her reliance on a rectilinear, geometric format for her compositions; and in her reference in the work to machines, plans, numbers, and mechanical parts. 

“We included them because they are extremely beautiful and visually powerful. Together they form an important group within her body of work.”

Making history

June and Leroy Schwarcz met in the late 1930s and were married in 1943. Two years later they moved to Chicago where Leroy would become chief mechanical engineer for the University of Chicago’s synchrocyclotron, which was at the time the highest-energy proton accelerator in the world.

Having studied art and design at the Pratt Institute in Brooklyn several years earlier, June found her way into a circle of notable artists in Chicago, including Bauhaus legend László Moholy-Nagy, founder of Chicago’s Institute of Design.

Around 1954, June was introduced to enameling and shortly thereafter began to exhibit her art. She and her husband had two children and relocated several times during the 1950s for Leroy’s work. In 1958 they settled in Sausalito, California, where June set up her studio in the lower level of their hillside home. 

In 1961, Leroy became the first mechanical engineer hired by Stanford University to work on “Project M,” which would become the famous 2-mile-long linear accelerator at SLAC. He oversaw the engineers during early design and construction of the linac, which eventually enabled Nobel-winning particle physics research.

June and Leroy’s daughter, Kim Schwarcz, who made a living as a glass blower and textile artist until the mid 1980s and occasionally exhibited with her mother, remembers those early days at the future lab.

“Before SLAC was built, the offices were in Quonset huts, and my father used to bring me down, and I would bicycle all over the campus,” she recalled. “Pief was a family friend and so was Bob Mozley. Mom introduced Bob to his future wife…It was a small community and a really nice community.” 

W.K.H. “Pief” Panofsky was the first director of SLAC; he and Mozley were renowned SLAC physicists and national arms control experts.

June Schwarcz, SLAC Drawing III, 1974, electroplated copper and enamel. (Photo by Cate Hurst) June Schwarcz, SLAC Drawing VII, 1975, electroplated copper and enamel. (Photo by Cate Hurst) June Schwarcz, SLAC Drawing VIII, 1975, electroplated copper and enamel. (Photo by Cate Hurst) June Schwarcz, SLAC Design Box, 1989, electroplated copper and enamel, mounted in a cherry box. (Photo by M. Lee Fatherree) June Schwarcz, Vessel, electroplated copper foil and enamel, sandblasted. (Photo by Cate Hurst) June Schwarcz, Bowl, 1980, electroplated copper foil and enamel, iron plated. (Photo by Gene Young) Previous Next Finding beauty

Kim was not surprised that her mother made art based on the SLAC drawings. She remembers June photographing the foggy view outside their home and getting inspiration from nature, ethnic art and Japanese clothing.

“She would take anything and make something out of it,” Kim said. “She did an enamel of an olive oil can once and a series called Adam’s Pants that were based on the droopy pants my son wore as a teen.”

But the fifteen SLAC-inspired compositions were unique and a family favorite; Kim and her brother Carl both own some of them, and others are at museums.

In a 2001 oral history interview with the Smithsonian Institution's Archives of American Art, June explained the detailed work involved in creating the SLAC drawings by varnishing, scribing, electroplating and enameling a copper sheet: “I'm primarily interested in having things that are beautiful, and of course, beauty is a complicated thing to devise, to find.”

Engineering art

Besides providing inspiration in the form of technical drawings, Leroy was influential in June’s career in other ways.

Around 1962 he introduced her to Jimmy Pope at the SLAC machine shop, who showed June how to do electroplating, a signature technique of her work. Electroplating involves using an electric current to deposit a coating of metal onto another material. She used it to create raised surfaces and to transform thin sheets of copper—which she stitched together using copper wire—into substantial, free-standing vessel-like forms. She then embellished these sculptures with colored enamel.

Leroy built a 30-gallon plating bath and other tools for June’s art-making at their shared workshop. 

“Mom was tiny, 5 feet tall, and she had these wobbly pieces on the end of a fork that she would put into a hot kiln. It was really heavy. Dad made a stand so she could rest her arm and slide the piece in,” Kim recalls.

“He was very inventive in that way, and very creative himself,” she said. “He did macramé in the 1960s, made wooden spoons and did scrimshaw carvings on bone that were really good.”

Kim remembers the lower-level workshop as a chaotic and inventive space. “For the longest time, there was a wooden beam in the middle of the workshop we would trip over. It was meant for a boat dad wanted to build—and eventually did build after he retired,” she said.

At SLAC Leroy’s work was driven by his “amazingly good intuition,” according to a tribute written by Mozley upon his colleague’s death in 1993. Even when he favored crude drawings to exact math, “his intuitive designs were almost invariably right,” he wrote. 

After the accelerator was built, Leroy turned his attention to the design, construction and installation of a streamer chamber scientists at SLAC used as a particle detector. In 1971 he took a leave of absence from the California lab to go back to Chicago and move the synchrocyclotron’s 2000-ton magnet from the university to Fermi National Accelerator Laboratory. 

“[Leroy] was the only person who could have done this because, although drawings existed, knowledge of the assembly procedures existed only in the minds of Leroy and those who had helped him put the cyclotron together,” Mozley wrote.

Beauty on display

June continued making art at her Sausalito home studio up until two weeks before her death in 2015 at the age of 97. A 2007 video shows the artist at work there 10 years prior to her passing. 

After Leroy died, her own art collection expanded on the shelves and walls of her home.

“As a kid, the art was just what mom did, and it never changed,” Kim remembers. “She couldn’t wait for us to go to school so she could get to work, and she worked through health challenges in later years.”

The Smithsonian exhibit is a unique collection of June’s celebrated work, with its traces of a shared history with SLAC and one of the lab’s first mechanical engineers.

“June had an exceptionally inquisitive mind, and we think you get a sense of the rich breadth of her vision in this wonderful body of work,” says curator Jazzar.

June Schwarcz: Invention and Variation is the first retrospective of the artist’s work in 15 years and includes almost 60 works. The exhibit runs through August 27 at the Smithsonian American Art Museum Renwick Gallery. 

Editor's note: Some of the information from this article was derived from an essay written by Jazzar and Nelson that appears in a book based on the exhibition with the same title.

A new model for standards

Tue, 07/11/2017 - 17:42

In an upcoming refresh, particle physics will define units of measurement such as the meter, the kilogram and the second.

While America remains obstinate about using Imperial units such as miles, pounds and degrees Fahrenheit, most of the world has agreed that using units that are actually divisible by 10 is a better idea. The metric system, also known as the International System of Units (SI), is the most comprehensive and precise system for measuring the universe that humans have developed. 

In 2018, the 26th General Conference on Weights and Measures will convene and likely adopt revised definitions for the seven base metric system units for measuring: length, mass, time, temperature, electric current, luminosity and quantity.

The modern metric system owes its precision to particle physics, which has the tools to investigate the universe more precisely than any microscope. Measurements made by particle physicists can be used to refine the definitions of metric units. In May, a team of German physicists at the Physikalisch-Technische Bundesanstalt made the most precise measurements yet of the Boltzmann constant, which will be used to define units of temperature.

Since the metric system was established in the 1790s, scientists have attempted to give increasingly precise definitions to these units. The next update will define every base unit using fundamental constants of the universe that have been derived by particle physics.

meter (distance): 

Starting in 1799, the meter was defined by a prototype meter bar, which was just a platinum bar. Physicists eventually realized that distance could be defined by the speed of light, which has been measured with an accuracy to one part in a billion using an interferometer (interestingly, the same type of detector the LIGO collaboration used to discover gravitational waves). The meter is currently defined as the distance traveled by light (in a vacuum) for 1/299,792,458 of a second, and will remain effectively unchanged in 2018.

kilogram (mass):

For over a century, the standard kilogram has been a small platinum-iridium cylinder housed at the International Bureau of Weights and Measures in France. But even its precise mass fluctuates due to factors such as accumulation of microscopic dust. Scientists hope to redefine the kilogram in 2018 by setting the value of Planck’s constant to exactly 6.626070040×1034 kilograms times meters squared per second. Planck’s constant is the smallest amount of quantized energy possible. This fundamental value, which is represented with the letter h, is integral to calculating energies in particle physics.

second (time):

The earliest seconds were defined as divisions of time between full moons. Later, seconds were defined by solar days, and eventually the time it took Earth to revolve around the sun. Today, seconds are defined by atomic time, which is precise to 1 part in 10 billion. Atomic time is calculated by periods of radiation by atoms, a measurement that relies heavily on particle physics techniques. One second is currently defined as 9,192,631,770 periods of the radiation for a Cesium-133 atom and will remain effectively unchanged. 

kelvin (temperature):

Kelvin is the temperature scale that starts at the coldest possible state of matter. Currently, a kelvin is defined by the triple point of water—where water can exist as a solid, liquid and gas. The triple point is 273.16 Kelvin, so a single kelvin is 1/273.16 of the triple point. But because water can never be completely pure, impurities can influence the triple point. In 2018 scientists hope to redefine kelvin by setting the value of Boltzmann’s constant to exactly 1.38064852×10−23 joules per kelvin. Boltzmann’s constant links the movement of particles in a gas (the average kinetic energy) to the temperature of the gas. Denoted by the symbol k, the Boltzmann constant is ubiquitous throughout physics calculations that involve temperature and entropy.  

ampere (electric current):

André-Marie Ampère, who is often considered the father of electrodynamics, has the honor of having the basic unit of electric current named after him. Right now, the ampere is defined by the amount of current required to produce of a force of 2×10−7 newtons for each meter between two parallel conductors of infinite length. Naturally, it’s a bit hard to come by things of infinite length, so the proposed definition is instead to define amperes by the fundamental charge of a particle. This new definition would rely on the charge of the electron, which will be set to 1.6021766208×10−19 amperes per second.

candela (luminosity):

The last of the base SI units to be established, the candela measures luminosity—what we typically refer to as brightness. Early standards for the candela used a phenomenon from quantum mechanics called “black body radiation.” This is the light that all objects radiate as a function of their heat. Currently, the candela is defined more fundamentally as 1/683 watt per square radian at a frequency of 540×1012 herz over a certain area, a definition which will remain effectively unchanged. Hard to picture? A candle, conveniently, emits about one candela of luminous intensity.

mole (quantity):

Different from all the other base units, the mole measures quantity alone. Over hundreds of years, scientists starting from Amedeo Avogadro worked to better understand how the number of atoms was related to mass, leading to the current definition of the mole: the number of atoms in 12 grams of carbon-12. This number, which is known as Avogadro’s constant and used in many calculations of mass in particle physics, is about 6 x 10^23. To make the mole more precise, the new definition would set Avogadro’s constant to exactly 6.022140857×1023, decoupling it from the kilogram.

Quirks of the arXiv

Fri, 07/07/2017 - 15:00

Sometimes, physics papers turn funny.

Since it went up in 1991, the arXiv (pronounced like the word “archive”) has been a hub for scientific papers in quantitative fields such as physics, math and computer science. Many of its million-plus papers are serious products of intense academic work that are later published in peer-reviewed journals. Still, some manage to have a little more character than the rest. For your consideration, we’ve gathered seven of the quirkiest physics papers on the arXiv.

Can apparent superluminal neutrino speeds be explained as a quantum weak measurement? M V Berry, N Brunner, S Popescu and P Shukla Read full paper (PDF)

In 2011, an experiment appeared to find particles traveling faster than the speed of light. To spare readers uninterested in lengthy calculations demonstrating the unlikeliness of this probably impossible phenomenon, the abstract for this analysis cut to the chase.

Quantum Tokens for Digital Signatures Shalev Ben-David and Or Sattath Read full paper (PDF)

Sometimes the best way to explain something is to think about how you might explain it to a child—for example, as a fairy tale.

A dialog on quantum gravity Carlo Rovelli Read full paper (PDF)

Unless you’re intimately familiar with string theory and quantum loop gravity, this Socratic dialogue is like Plato’s Republic: It’s all Greek to you.

The Proof of Innocence Dmitri Krioukov Read full paper (PDF)

Pulled over after he was apparently observed failing to halt at a stop sign, the author of this paper, Dmitri Krioukov, was determined to prove his innocence—as only a scientist would.

Using math, he demonstrated that, to a police officer measuring the angular speed of Krioukov’s car, a brief obstruction from view could cause an illusion that the car did not stop. Krioukov submitted his proof to the arXiv; the judge ruled in his favor.

Quantum weak coin flipping with arbitrarily small bias Carlos Mochon Read full paper (PDF)

Not many papers in the arXiv illustrate their point with a tale involving human sacrifice. There’s something about quantum informatics that brings out the weird side of physicists.

10 = 6 + 4 Frank D. (Tony) Smith, Jr. Read full paper (PDF)

A theorist calculated an alternative decomposition of 10 dimensions into 6 spacetime dimensions with local Conformal symmetry and 4-dimensional compact Internal Symmetry Space. For the title of his paper, he decided to go with something a little simpler.

Would Bohr be born if Bohm were born before Born? Hrvoje Nikolic Read full paper (PDF)

This tricky tongue-twisting treatise theorizes a tangential timeline to testify that taking up quantum theories turns on timeliness.

When was the Higgs actually discovered?

Mon, 07/03/2017 - 23:50

The announcement on July 4 was just one part of the story. Take a peek behind the scenes of the discovery of the Higgs boson.

Joe Incandela sat in a conference room at CERN and watched with his arms folded as his colleagues presented the latest results on the hunt for the Higgs boson. It was December 2011, and they had begun to see the very thing they were looking for—an unexplained bump emerging from the data.

“I was far from convinced,” says Incandela, a professor at the University of California, Santa Barbara and the former spokesperson of the CMS experiment at the Large Hadron Collider.

For decades, scientists had searched for the elusive Higgs boson: the holy grail of modern physics and the only piece of the robust and time-tested Standard Model that had yet to be found.

The construction of the LHC was motivated in large part by the absence of this fundamental component from our picture of the universe. Without it, physicists couldn’t explain the origin of mass or the divergent strengths of the fundamental forces.

“Without the Higgs boson, the Standard Model falls apart,” says Matthew McCullough, a theorist at CERN. “The Standard Model was fitting the experimental data so well that most of the theory community was convinced that something playing the role of Higgs boson would be discovered by the LHC.”

The Standard Model predicted the existence of the Higgs but did not predict what the particle’s mass would be. Over the years, scientists had searched for it across a wide range of possible masses. By 2011, there was only a tiny region left to search; everything else had been excluded by previous generations of experimentation. If the predicted Higgs boson were anywhere, it had to be there, right where the LHC scientists were looking.

But Incandela says he was skeptical about these preliminary results. He knew that the Higgs could manifest itself in many different forms, and this particular channel was extremely delicate.

“A tiny mistake or an unfortunate distribution of the background events could make it look like a new particle is emerging from the data when in reality, it’s nothing,” Incandela says.

A common mantra in science is that extraordinary claims require extraordinary evidence. The challenge isn’t just collecting the data and performing the analysis; it’s deciding if every part of the analysis is trustworthy. If the analysis is bulletproof, the next question is whether the evidence is substantial enough to claim a discovery. And if a discovery can be claimed, the final question is what, exactly, has been discovered? Scientists can have complete confidence in their results but remain uncertain about how to interpret them.

In physics, it’s easy to say what something is not but nearly impossible to say what it is. A single piece of corroborated, contradictory evidence can discredit an entire theory and destroy an organization’s credibility.

“We’ll never be able to definitively say if something is exactly what we think it is, because there’s always something we don’t know and cannot test or measure,” Incandela says. “There could always be a very subtle new property or characteristic found in a high-precision experiment that revolutionizes our understanding.”

With all of that in mind, Incandela and his team made a decision: From that point on, everyone would refine their scientific analyses using special data samples and a patch of fake data generated by computer simulations covering the interesting areas of their analyses. Then, when they were sure about their methodology and had enough data to make a significant observation, they would remove the patch and use their algorithms on all the real data in a process called unblinding.

“This is a nice way of providing an unbiased view of the data and helps us build confidence in any unexpected signals that may be appearing, particularly if the same unexpected signal is seen in different types of analyses,” Incandela says.

A few weeks before July 4, all the different analysis groups met with Incandela to present a first look at their unblinded results. This time the bump was very significant and showing up at the same mass in two independent channels.

“At that point, I knew we had something,” Incandela says. “That afternoon we presented the results to the rest of the collaboration. The next few weeks were among the most intense I have ever experienced.”

Meanwhile, the other general-purpose experiment at the LHC, ATLAS, was hot on the trail of the same mysterious bump.

Andrew Hard was a graduate student at The University of Wisconsin, Madison working on the ATLAS Higgs analysis with his PhD thesis advisor Sau Lan Wu.

“Originally, my plan had been to return home to Tennessee and visit my parents over the winter holidays,” Hard says. “Instead, I came to CERN every day for five months—even on Christmas. There were a few days when I didn't see anyone else at CERN. One time I thought some colleagues had come into the office, but it turned out to be two stray cats fighting in the corridor.”

Hard was responsible for writing the code that selected and calibrated the particles of light the ATLAS detector recorded during the LHC’s high-energy collisions. According to predictions from the Standard Model, the Higgs can transform into two of these particles when it decays, so scientists on both experiments knew that this project would be key to the discovery process.

“We all worked harder than we thought we could,” Hard says. “People collaborated well and everyone was excited about what would come next. All in all, it was the most exciting time in my career. I think the best qualities of the community came out during the discovery.”

At the end of June, Hard and his colleagues synthesized all of their work into a single analysis to see what it revealed. And there it was again—that same bump, this time surpassing the statistical threshold the particle physics community generally requires to claim a discovery.

“Soon everyone in the group started running into the office to see the number for the first time,” Hard says. “The Wisconsin group took a bunch of photos with the discovery plot.”

Hard had no idea whether CMS scientists were looking at the same thing. At this point, the experiments were keeping their latest results secret—with the exception of Incandela, Fabiola Gianotti (then ATLAS spokesperson) and a handful of CERN’s senior management, who regularly met to discuss their progress and results.

“I told the collaboration that the most important thing was for each experiment to work independently and not worry about what the other experiment was seeing,” Incandela says. “I did not tell anyone what I knew about ATLAS. It was not relevant to the tasks at hand.”

Still, rumors were circulating around theoretical physics groups both at CERN and abroad. Mccullough, then a postdoc at the Massachusetts Institute of Technology, was avidly following the progress of the two experiments.

“We had an update in December 2011 and then another one a few months later in March, so we knew that both experiments were seeing something,” he says. “When this big excess showed up in July 2012, we were all convinced that it was the guy responsible for curing the ails of the Standard Model, but not necessarily precisely that guy predicted by the Standard Model. It could have properties mostly consistent with the Higgs boson but still be not absolutely identical.”

The week before announcing what they’d found, Hard’s analysis group had daily meetings to discuss their results. He says they were excited but also nervous and stressed: Extraordinary claims require extraordinary confidence.

“One of our meetings lasted over 10 hours, not including the dinner break halfway through,” Hard says. “I remember getting in a heated exchange with a colleague who accused me of having a bug in my code.”

After both groups had independently and intensely scrutinized their Higgs-like bump through a series of checks, cross-checks and internal reviews, Incandela and Gianotti decided it was time to tell the world.

“Some people asked me if I was sure we should say something,” Incandela says. “I remember saying that this train has left the station. This is what we’ve been working for, and we need to stand behind our results.”

On July 4, 2012, Incandela and Gianotti stood before an expectant crowd and, one at a time, announced that decades of searching and generations of experiments had finally culminated in the discovery of a particle “compatible with the Higgs boson.”

Science journalists rejoiced and rushed to publish their stories. But was this new particle the long-awaited Higgs boson? Or not?

Discoveries in science rarely happen all at once; rather, they build slowly over time. And even when the evidence overwhelmingly points in a clear direction, scientists will rarely speak with superlatives or make definitive claims.

“There is always a risk of overlooking the details,” Incandela says, “and major revolutions in science are often born in the details.”

Immediately after the July 4 announcement, theorists from around the world issued a flurry of theoretical papers presenting alternative explanations and possible tests to see if this excess really was the Higgs boson predicted by the Standard Model or just something similar.

“A lot of theory papers explored exotic ideas,” McCullough says. “It’s all part of the exercise. These papers act as a straw man so that we can see just how well we understand the particle and what additional tests need to be run.”

For the next several months, scientists continued to examine the particle and its properties. The more data they collected and the more tests they ran, the more the discovery looked like the long-awaited Higgs boson. By March, both experiments had twice as much data and twice as much evidence.

“Amongst ourselves, we called it the Higgs,” Incandela says, “but to the public, we were more careful.”

It was increasingly difficult to keep qualifying their statements about it, though. “It was just getting too complicated,” Incandela says. “We didn’t want to always be in this position where we had to talk about this particle like we didn’t know what it was.”

On March 14, 2013—nine months and 10 days after the original announcement—CERN issued a press release quoting Incandela as saying, “to me, it is clear that we are dealing with a Higgs boson, though we still have a long way to go to know what kind of Higgs boson it is.”​

To this day, scientists are open to the possibility that the Higgs they found is not exactly the Higgs they expected.

“We are definitely, 100 percent sure that this is a Standard-Model-like Higgs boson,” Incandela says. “But we’re hoping that there’s a chink in that armor somewhere. The Higgs is a sign post, and we’re hoping for a slight discrepancy which will point us in the direction of new physics.”

What’s really happening during an LHC collision?

Fri, 06/30/2017 - 18:40

It’s less of a collision and more of a symphony.

The Large Hadron Collider is definitely large. With a 17-mile circumference, it is the biggest collider on the planet. But the latter fraction of its name is a little misleading. That’s because what collides in the LHC are the tiny pieces inside the hadrons, not the hadrons themselves.

Hadrons are composite particles made up of quarks and gluons. The gluons carry the strong force, which enables the quarks to stick together and binds them into a single particle. The main fodder for the LHC are hadrons called protons. Protons are made up of three quarks and an indefinable number of gluons. (Protons in turn make up atoms, which are the building blocks of everything around us.)

If a proton were enlarged to the size of a basketball, it would look empty. Just like atoms, protons are mostly empty space. The individual quarks and gluons inside are known to be extremely small, less than 1/10,000th the size of the entire proton.

“The inside of a proton would look like the atmosphere around you,” says Richard Ruiz, a theorist at Durham University. “It’s a mixture of empty space and microscopic particles that, for all intents and purposes, have no physical volume.

“But if you put those particles inside a balloon, you’ll see the balloon expand. Even though the internal particles are microscopic, they interact with each other and exert a force on their surroundings, inevitably producing something which does have an observable volume.”

So how do you collide two objects that are effectively empty space? You can’t. But luckily, you don’t need a classical collision to unleash a particle’s full potential.

In particle physics, the term “collide” can mean that two protons glide through each other, and their fundamental components pass so close together that they can talk to each other. If their voices are loud enough and resonate in just the right way, they can pluck deep hidden fields that will sing their own tune in response—by producing new particles.

“It’s a lot like music,” Ruiz says. “The entire universe is a symphony of complex harmonies which call and respond to each other. We can easily produce the mid-range tones, which would be like photons and muons, but some of these notes are so high that they require a huge amount of energy and very precise conditions to resonate.”

Space is permeated with dormant fields that can briefly pop a particle into existence when vibrated with the right amount of energy. These fields play important roles but almost always work behind the scenes. The Higgs field, for instance, is always interacting with other particles to help them gain mass. But a Higgs particle will only appear if the field is plucked with the right resonance.

When protons meet during an LHC collision, they break apart and the quarks and gluons come spilling out. They interact and pull more quarks and gluons out of space, eventually forming a shower of fast-moving hadrons.

This subatomic symbiosis is facilitated by the LHC and recorded by the experiment, but it’s not restricted to the laboratory environment; particles are also accelerated by cosmic sources such as supernova remnants. “This happens everywhere in the universe,” Ruiz says. “The LHC and its experiments are not special in that sense. They’re more like a big concert hall that provides the energy to pop open and record the symphony inside each proton.”

The rise of LIGO’s space-studying super-team

Tue, 06/27/2017 - 16:27

The era of multi-messenger astronomy promises rich rewards—and a steep learning curve.

Sometimes you need more than one perspective to get the full story.

Scientists including astronomers working with the Fermi Large Area Telescope have recorded brief bursts of high-energy photons called gamma rays coming from distant reaches of space. They suspect such eruptions result from the merging of two neutron stars—the collapsed cores of dying stars—or from the collision of a neutron star and a black hole. 

But gamma rays alone can’t tell them that. The story of the dense, crashing cores would be more convincing if astronomers saw a second signal coming from the same event—for example, the release of ripples in space-time called gravitational waves.

“The Fermi Large Area Telescope detects a few short gamma ray bursts per year already, but detecting one in correspondence to a gravitational-wave event would be the first direct confirmation of this scenario,” says postdoctoral researcher Giacomo Vianello of the Kavli Institute for Particle Astrophysics and Cosmology, a joint institution of SLAC National Accelerator Laboratory and Stanford University.

Scientists discovered gravitational waves in 2015 (announced in 2016). Using the Laser Interferometer Gravitational-Wave Observatory, or LIGO, they detected the coalescence of two massive black holes.

LIGO scientists are now sharing their data with a network of fellow space watchers to see if any of their signals match up. Combining multiple signals to create a more complete picture of astronomical events is called multi-messenger astronomy.​

Looking for a match

“We had this dream of finding astronomical events to match up with our gravitational wave triggers,” says LIGO scientist Peter Shawhan of the University of Maryland. ​

But LIGO can only narrow down the source of its signals to a region large enough to contain roughly 100,000 galaxies. 

Searching for contemporaneous signals within that gigantic volume of space is extremely challenging, especially since most telescopes only view a small part of the sky at a time. So Shawhan and his colleagues developed a plan to send out an automatic alert to other observatories whenever LIGO detected an interesting signal of its own. The alert would contain preliminary calculations and the estimated location of the source of the potential gravitational waves.

“Our early efforts were pretty crude and only involved a small number of partners with telescopes, but it kind of got this idea started,” Shawhan says. The LIGO Collaboration and the Virgo Collaboration, its European partner, revamped and expanded the program while upgrading their detectors. Since 2014, 92 groups have signed up to receive alerts from LIGO, and the number is growing. 

LIGO is not alone in latching onto the promise of multi-messenger astronomy. The Supernova Early Warning System (SNEWS) also unites multiple experiments to look at the same event in different ways. Neutral, rarely interacting particles called neutrinos escape more quickly from collapsing stars than optical light, so a network of neutrino experiments is prepared to alert optical observatories as soon as they get the first warning of a nearby supernova in the form of a burst of neutrinos. 

National Science Foundation Director France Córdova has lauded multi-messenger astronomy, calling it in 2016 a bold research idea that would lead to transformative discoveries.​

The learning curve

Catching gamma ray bursts alongside gravitational waves is no simple feat. 

The Fermi Large Area Telescope orbits the earth as the primary instrument on the Fermi Gamma-ray Space Telescope. The telescope is constantly in motion and has a large field of view that surveys the entire sky multiple times per day. 

But a gamma-ray burst lasts just a few seconds, and it takes about three hours for LAT to complete its sweep. So even if an event that releases gravitational waves also produces a gamma-ray burst, LAT might not be looking in the right direction at the right time. It would need to catch the afterglow of the event. 

Fermi LAT scientist Nicola Omodei of Stanford University acknowledges another challenge: The window to see the burst alongside gravitational waves might not line up with the theoretical predictions. It’s never been done before, so the signal could look different or come at a different time than expected. 

That doesn’t stop him and his colleagues from trying, though. “We want to cover all bases, and we adopt different strategies,” he says. “To make sure we are not missing any preceding or delayed signal, we also look on much longer time scales, analyzing the days before and after the trigger.”

Scientists using the second instrument on the Fermi Gamma-ray Space Telescope have already found an unconfirmed signal that aligned with the first gravitational waves LIGO detected, says scientist Valerie Connaughton of the Universities Space Research Association, who works on the Gamma-Ray Burst Monitor. “We were surprised to find a transient event 0.4 seconds after the first GW seen by LIGO.”

While the event is theoretically unlikely to be connected to the gravitational wave, she says the timing and location “are enough for us to be interested and to challenge the theorists to explain how something that was not expected to produce gamma rays might have done so.”

From the ground up

It’s not just space-based experiments looking for signals that align with LIGO alerts. A working group called DESgw, members of the Dark Energy Survey with independent collaborators, have found a way to use the Dark Energy Camera, a 570-Megapixel digital camera mounted on a telescope in the Chilean Andes, to follow up on gravitational wave detections.​

“We have developed a rapid response system to interrupt the planned observations when a trigger occurs,” says DES scientist Marcelle Soares-Santos of Fermi National Accelerator Laboratory. “The DES is a cosmological survey; following up gravitational wave sources was not originally part of the DES scientific program.” 

Once they receive a signal, the DESgw collaborators meet to evaluate the alert and weigh the cost of changing the planned telescope observations against what scientific data they could expect to see—most often how much of the LIGO source location could be covered by DECam observations.

“We could, in principle, put the telescope onto the sky for every event as soon as night falls,” says DES scientist Jim Annis, also of Fermilab. “In practice, our telescope is large and the demand for its time is high, so we wait for the right events in the right part of the sky before we open up and start imaging.”

At an even lower elevation, scientists at the IceCube neutrino experiment—made up of detectors drilled down into Antarctic ice—are following LIGO’s exploits as well.

“The neutrinos IceCube is looking for originate from the most extreme environment in the cosmos,” says IceCube scientist Imre Bartos of Columbia University. “We don't know what these environments are for sure, but we strongly suspect that they are related to black holes.”

LIGO and IceCube are natural partners. Both gravitational waves and neutrinos travel for the most part unimpeded through space. Thus, they carry pure information about where they originate, and the two signals can be monitored together nearly in real time to help refine the calculated location of the source.

The ability to do this is new, Bartos says. Neither gravitational waves nor high-energy neutrinos had been detected from the cosmos when he started working on IceCube in 2008. “During the past few years, both of them were discovered, putting the field on a whole new footing.”

Shawhan and the LIGO collaboration are similarly optimistic about the future of their program and multi-messenger astronomy. More gravitational wave detectors are planned or under construction, including an upgrade to the European detector Virgo, the KAGRA detector in Japan, and a third LIGO detector in India, and that means scientists will home in closer and closer on their targets.​

World’s biggest neutrino experiment moves one step closer

Fri, 06/23/2017 - 18:57

The startup of a 25-ton test detector at CERN advances technology for the Deep Underground Neutrino Experiment.

In a lab at CERN sits a very important box. It covers about three parking spaces and is more than a story tall. Sitting inside is a metal device that tracks energetic cosmic particles.

This is a prototype detector, a stepping-stone on the way to the future Deep Underground Neutrino Experiment (DUNE). On June 21, it recorded its first particle tracks.

So begins the largest ever test of an extremely precise method for measuring elusive particles called neutrinos, which may hold the key to why our universe looks the way it does and how it came into being.

A two-phase detector

The prototype detector is named WA105 3x1x1 (its dimensions in meters) and holds five active tons—3000 liters—of liquid argon. Argon is well suited to interacting with neutrinos then transmitting the subsequent light and electrons for collection. Previous liquid argon neutrino detectors, such as ICARUS and MicroBooNE, detected signals from neutrinos using wires in the liquid argon. But crucially, this new test detector also holds a small amount of gaseous argon, earning it the special status of a two-phase detector.

As particles pass through the detector, they interact with the argon atoms inside. Electrons are stripped off of atoms and drift through the liquid toward an “extraction grid,” which kicks them into the gas. There, large electron multipliers create a cascade of electrons, leading to a stronger signal that scientists can use to reconstruct the particle track in 3D. Previous tests of this method were conducted in small detectors using about 250 active liters of liquid argon.

“This is the first time anyone will demonstrate this technology at this scale,” says Sebastien Murphy, who led the construction of the detector at CERN.

The 3x1x1 test detector represents a big jump in size compared to previous experiments, but it’s small compared to the end goal of DUNE, which will hold 40,000 active tons of liquid argon. Scientists say they will take what they learn and apply it (and some of the actual electronic components) to next-generation single- and dual-phase prototypes, called ProtoDUNE.

The technology used for both types of detectors is a time projection chamber, or TPC. DUNE will stack many large modules snugly together like LEGO blocks to create enormous DUNE detectors, which will catch neutrinos a mile underground at Sanford Underground Research Facility in South Dakota. Overall development for liquid argon TPCs has been going on for close to 40 years, and research and development for the dual-phase for more than a decade. The idea for this particular dual-phase test detector came in 2013.

“The main goal [with WA105 3x1x1] is to demonstrate that we can amplify charges in liquid argon detectors on the same large scale as we do in standard gaseous TPCs,” Murphy says.

By studying neutrinos and antineutrinos that travel 800 miles through the Earth from the US Department of Energy’s Fermi National Accelerator Laboratory to the DUNE detectors, scientists aim to discover differences in the behavior of matter and antimatter. This could point the way toward explaining the abundance of matter over antimatter in the universe. The supersensitive detectors will also be able to capture neutrinos from exploding stars (supernovae), unveiling the formation of neutron stars and black holes. In addition, they allow scientists to hunt for a rare phenomenon called proton decay.

“All the R&D we did for so many years and now want to do with ProtoDUNE is the homework we have to do,” says André Rubbia, the spokesperson for the WA105 3x1x1 experiment and former co-spokesperson for DUNE. “Ultimately, we are all extremely excited by the discovery potential of DUNE itself.”

One of the first tracks in the prototype detector, caused by a cosmic ray.

André Rubbia Testing, testing, 3-1-1, check, check

Making sure a dual-phase detector and its electronics work at cryogenic temperatures of minus 184 degrees Celsius (minus 300 degrees Fahrenheit) on a large scale is the primary duty of the prototype detector—but certainly not its only one. The membrane that surrounds the liquid argon and keeps it from spilling out will also undergo a rigorous test. Special cryogenic cameras look for any hot spots where the liquid argon is predisposed to boiling away and might cause voltage breakdowns near electronics.

After many months of hard work, the cryogenic team and those working on the CERN neutrino platform have already successfully corrected issues with the cryostat, resulting in a stable level of incredibly pure liquid argon. The liquid argon has to be pristine and its level just below the large electron multipliers so that the electrons from the liquid will make it into the gaseous argon.

“Adding components to a detector is never trivial, because you’re adding impurities such as water molecules and even dust,” says Laura Manenti, a research associate at the University College London in the UK. “That is why the liquid argon in the 311—and soon to come ProtoDUNEs—has to be recirculated and purified constantly.”

While ultimately the full-scale DUNE detectors will sit in the most intense neutrino beam in the world, scientists are testing the WA105 3x1x1 components using muons from cosmic rays, high-energy particles arriving from space. These efforts are supported by many groups, including the Department of Energy’s Office of Science.

The plan is now to run the experiment, gather as much data as possible, and then move on to even bigger territory.

“The prospect of starting DUNE is very exciting, and we have to deliver the best possible detector,” Rubbia says. “One step at a time, we’re climbing a large mountain. We’re not at the top of Everest yet, but we’re reaching the first chalet.”

Howie Day records love song to physics

Fri, 06/23/2017 - 14:42

After the musician learned that grad students at CERN had created a parody of his 2004 single “Collide,” he flew to Switzerland to sing it at the LHC.

Singer-songwriter Howie Day was sitting in a coffee shop in Denver one morning while on tour when he saw the Twitter notifications: CERN had shared a parody video of his hit song “Collide,” sung from the perspective of a proton in the Large Hadron Collider.

Sarah Charley, US communications manager for the LHC experiments, had come up with the idea for the video. She created it with the help of graduate students Jesse Heilman of the University of California, Riverside and Tom Perry and Laser Seymour Kaplan of the University of Wisconsin, Madison.

They spent lunches and coffee breaks workshopping their new version of the lyrics, which were originally about two people falling in love despite their differences. They spent a combined 20 hours in CERN’s editing studio recording the vocals and instrumentation of the track. Then they wandered around the laboratory for a full Saturday, filming at various sites. Charley edited the footage together.

“I was flattered, and it was quite funny, too,” Day says of seeing the video for the first time. “I immediately retweeted it and then sent a direct message inquiring about a visit. I figured it was a long shot, but why not?”

That started a conversation that led to Day planning a visit to CERN and booking time in his studio to re-record the song from the ground up with the new lyrics. “It was about the most fun I've ever had in the studio,” Day says. “We literally laughed all day long. I sent the track off to CERN with the note, ‘Should we make another music video?’”

The answer was yes.

While at CERN, Day spent two days visiting the ATLAS and CMS experiments, the CERN Data Centre and the SM18 magnet-testing facility. He also was given the rare opportunity to travel down into the LHC tunnel. CERN’s video crew tagged along to film him at the various sites.

“Going down into the LHC tunnel was a once in a lifetime opportunity, and it felt that way. It was like seeing the northern lights, or playing the Tonight Show, or bringing a new puppy home.”

Day, who says he has always been fascinated by the “why” of things, had been aware of CERN before this project, but he had only a rough idea of what went on there. He says that it wasn’t until he got there that things started to make sense.

“Obviously nothing can prepare you for the sheer scale of the place, but also the people who worked there were amazing,” Day says. “I felt completely overwhelmed and humbled the entire time. It was truly great to be working at the site where humans may make the most important scientific discoveries of our lifetime.”

Heilman, now a postdoctoral researcher at Carleton University, says that he saw the song as a way to reach out to people outside the culture of academia.

“All of us have been steeped in the science for so long that we sort of forget how to speak a language,” he says. “It's always important for academics and researchers to learn different ways to communicate what we’re doing because we’re doing it for people and for society.”

There’s a point in the original song where there’s an emotional build, he says, and Day sings, “I’ve found I’m scared to know, I’m always on your mind.”

The parody uses that part of the song to express the hopes and fears of experimentalists looking for evidence that might not ever appear.

“We're all experimentalists, so we will all spend our careers searching for something,” Heilman says. “The feeling is that [the theory of] supersymmetry, while it's this thing that everybody's been so excited about for a long time, really doesn’t seem that likely to a lot of us anymore because we’re eliminating a lot of the phase space. It's sort of like this white whale hunt. And so our lyrics, ‘Can SUSY still be found?’ is this emotional cry to the physics.”

Charley says she hopes that, through the video, they’re able to “reach and touch people with the science who we normally can't talk to.”

“I think you can appreciate something without fully understanding it,” she says. “As someone who is a professional science communicator, that's always the line I'm walking: trying to find ways that people can appreciate and understand and value something without needing to get a PhD. You can't devote your life to everything, but you can still have an appreciation for things in the world outside your own specific field.”

African School works to develop local expertise

Thu, 06/22/2017 - 16:40

Universities in sub-Saharan Africa are teaming up to offer free training to students interested in fundamental physics.

Last Feremenga was born in a small town in Zimbabwe. As a high school student in a specialized school in the capital, Harare, he was drawn to the study of physics.

“Physics was at the top of my list of potential academic fields to pursue,” he says.

But with limited opportunities nearby, that was going to require a lot of travel.

With help from the US Education Assistance Center at the American Embassy in Harare, Feremenga was accepted at the University of Chicago in 2007. As an undergraduate, he conducted research for a year at the nearby US Department of Energy’s Fermi National Accelerator Laboratory.

Then, through the University of Texas at Arlington, he became one of just a handful of African nationals to conduct research as a user at European research center CERN. Feremenga joined the ATLAS experiment at the Large Hadron Collider. He spent his grad-school years traveling between CERN and Argonne National Laboratory near Chicago, analyzing hundreds of terabytes of ATLAS data.

“I became interested in solving problems across diverse disciplines, not just physics,” he says.

“At CERN and Argonne, I assisted in developing a system that filters interesting events from large data-sets. I also analyzed these large datasets to find interesting physics patterns.”

The African School of Fundamental Physics and Applications

In December 2016, he received his PhD. In February 2017, he accepted a job at technology firm Digital Reasoning in Nashville, Tennessee.

To pursue particle physics, Feremenga needed to spend the entirety of his higher education outside Zimbabwe. Only one activity brought him even within the same continent as his home: the African School of Fundamental Physics and Applications. Feremenga attended the school in the program’s inaugural year at South Africa’s Stellenbosch University.

The ASP received funding for a year from France’s Centre National de la Recherche Scientific (CNRS) in 2008. Since then, major supporters among 20 funding institutions have included the International Center for Theoretical Physics (ICTP) in Trieste, Italy; the South African National Research Foundation, and department of Science and Technology; and the South African Institute of Physics. Other major supporters have included CERN, the US National Science Foundation and the University of Rwanda.

The free, three-week ASP has been held bi-annually since 2010. Targeting students in sub-Saharan Africa, the school has been held in South Africa, Ghana, Senegal and Rwanda. The 2018 School is slated to take place in Namibia. Thanks to outreach efforts, applications have risen from 125 in 2010 to 439 in 2016.

The African School of Fundamental Physics and Applications

The free, three-week ASP has been held bi-annually since 2010. Targeting students in sub-Saharan Africa, the school has been held in South Africa, Ghana, Senegal and Rwanda. The 2018 School is slated to take place in Namibia. Thanks to outreach efforts, applications have risen from 125 in 2010 to 439 in 2016.

The 50 to 80 students selected for the school must have a minimum of a 3-year university education in math, physics, engineering and/or computer science. The first week of the school focuses on theoretical physics; the second week, experimental physics; the third week, physics applications and high-performance computing.

School organizers stay in touch to support alumni in pursuing higher education, says organizer Ketevi Assamagan. “We maintain contact with the students and help them as much as we can,” Assamagan says. “ASP alumni are pursuing higher education in Africa, Asia, Europe and the US.”

Assamagan, originally from Togo but now a US citizen, worked on the Higgs hunt with the ATLAS experiment. He is currently at Brookhaven National Lab in New York, which supports him devoting 10 percent of his time to the ASP.

While sub-Saharan countries are just beginning to close the gap in physics, there is one well-established accelerator complex in South Africa, operated by the iThemba LABS of Cape Town and Johannesburg. The 30-year-old Separated-Sector Cyclotron, which primarily produces particle beams for nuclear research and for training at the postdoc level, is the largest accelerator of its kind in the southern hemisphere.

Jonathan Dorfan, former Director of SLAC National Accelerator Laboratory and a native of South Africa, attended University of Cape Town. Dorfan recalls that after his Bachelor’s and Master’s degrees, the best PhD opportunities were in the US or Britain. He says he’s hopeful that that outlook could one day change.

Organizers of the African School of Fundamental Physics and Applications continue reaching out to students on the continent in the hopes that one day, someone like Feremenga won’t have to travel across the world to pursue particle physics.