symmetry

Waiting for a sign

Some scientists spend decades trying to catch a glimpse of a rare process. But with good experimental design and a lot of luck, they often need only a handful of signals to make a discovery. In 2009, University of Naples physicist Gio... Continue reading

Q&A: Planning Europe’s physics future

Halina Abramowicz leads the group effort to decide the future of European particle physics. Physics projects are getting bigger, more global, more collaborative and more advanced than ever—with long lead times for complex physics mach... Continue reading

New facility aims to shrink accelerators

Work has begun on an upgrade to the Facility for Advanced Accelerator Experimental Tests at SLAC National Accelerator Laboratory. The Department of Energy’s SLAC National Accelerator Laboratory has started to assemble a new facility for rev... Continue reading

Intriguing news from MiniBooNE

New research results have potentially identified a fourth type of neutrino: the sterile neutrino.

Photomultipliers arranged in a spiral inside the MiniBooNE experiment

New research results have potentially identified a fourth type of neutrino, a “sterile neutrino” particle. This particle will provide challenges for the Standard Model of particle physics if it is found to be a valid result in future experiments. The work, conducted by a multi-institutional team at Fermi National Accelerator Laboratory near Chicago, confirms results found in the 1990s in the Los Alamos Liquid Scintillator Neutrino Detector (LSND).

“This is a fascinating step forward for particle physics,” says Los Alamos National Laboratory Director Terry Wallace. “Of course, this needs to be tempered by ‎the fact that future observations are required to really clinch this beyond any shadow of doubt. Modifications to the Standard Model, including dark matter, new particles and other interpretations of this result are still speculative. What stands with high confidence is that two experiments with completely different approaches observe the same effect.”

Neutrinos, traditionally understood to come in three flavors (electron, muon and tau), have been measured by the Mini Booster Neutrino Experiment, MiniBooNE, for some 15 years. The key to the current result is the existence of more electron-flavored neutrinos than expected. Neutrinos normally oscillate between the three types, but the overpopulation of the electron-flavored ones leads to a theory that some of the muon neutrinos became sterile neutrinos for a time during the regular oscillations. The sterile neutrinos could reasonably be assumed to have transitioned into electron neutrinos in their next oscillation phase, thus explaining the higher electron numbers.

“We cannot say definitively that it’s sterile neutrinos, but we can conclusively say something fundamental is going on,” says Richard Van de Water, the Los Alamos co-lead on the project.

“Over the past 20 to 30 years, neutrino oscillations have been observed from one flavor to another,” he says. “But in the late 1990s the LSND at Los Alamos saw evidence of electron neutrinos in the beam, and if our observations were correct, a much heavier type of neutrino was also in existence. That’s where the idea of sterile neutrinos came about."

The MiniBooNE experiment was designed differently from LSND, yet has shown similar results.

“I’m careful about saying it’s sterile neutrinos. It could be, but it could be something else," Van de Water says. "The same effect has now been observed in two experiments, with a small chance that there is a mistake in both experiments. We still see what shouldn’t be there, and it could be even more exciting. Speculating, I like to think of this as the first hint of the dark sector, perhaps interacting through neutrinos, and this could be a way to probe dark matter and dark energy.”

In a recent article, Fermilab's deputy director for research noted that the latest results from the MiniBooNE collaboration provide even stronger motivation for the three new short-baseline neutrino experiments at Fermilab that are based on liquid argon technology.

“These are exciting times for neutrino scientists,” Lykken says.

The MiniBooNE detector was established by a collaborative effort at Fermilab in 2002 to search for unusual neutrino interactions. In recent years the detector has collected data to study background interactions related to the short-baseline neutrino program. About 50 scientists from 20 institutions continue to work on the analysis of data recorded by the experiment.

Editor's note: A version of this article was originally published as a Los Alamos National Laboratory press release.

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The perfect couple: Higgs and top quark spotted together

Physicists see top quarks and Higgs bosons emanating from the same collisions in new results from the Large Hadron Collider.

Split screen image shows the CMS and ATLAS detectors at CERN.

Today two experiments at the Large Hadron Collider at CERN announced a discovery that finally links the two heaviest known particles: the top quark and the Higgs boson. The CMS and ATLAS experiments have seen simultaneous production of both particles during a rare subatomic process. This is the first time scientists have measured the Higgs boson’s direct interaction with top quarks.

“This observation connects for the first time directly the two heaviest elementary particles of the Standard Model: the top quark, which was discovered in 1995 at the Tevatron by the CDF and DZero experiments, and the Higgs boson,” says Boaz Klima, a scientist at the US Department of Energy’s Fermi National Accelerator Laboratory and the CMS publication board chair.

The Higgs boson was predicted in the 1960s and discovered by the CMS and ATLAS experiments in 2012 using particle collisions generated by the LHC.

Fundamental particles gain mass through their interaction with the Higgs field, so it would make sense that the top quark—the most massive particle ever discovered—would have a strong coupling with the Higgs boson. But scientists say they need to test every aspect of the theory in order to fully verify it.

Before its discovery, theorists had a good picture of how the Higgs boson was supposed to behave, according to the Standard Model of particle physics. Now that LHC physicists can nimbly produce and study Higgs bosons, the next step is to scrutinize these predictions and see if they hold water. A big question has been whether the Higgs boson can interact with quarks and, if so, what this relationship might look like.

“The Higgs boson was originally predicted because it helped explain why some force-carrying bosons had mass while others remained massless,” says Anadi Canepa, the new head of the CMS Department at Fermilab. “However, the Higgs also endows quarks with mass. ”

Even though scientists suspected that the Higgs boson interacts more strongly with the massive top quark than any other, all evidence until recently has been below the threshold required to claim a discovery. These new results—one paper published today in Physical Review Letters from the CMS collaboration and another paper submitted by the ATLAS collaboration—show definitively that the Higgs boson communicates with the top quark as predicted and opens up a new door to explore these interactions further.

The top quark played a key role in Higgs research even before scientists found the Higgs. Theorists used measurements of the top quark to help them narrow in on the mass of the Higgs boson prior to its discovery, and the top quark is helping physicists understand the strength of the Higgs field at different energies. The top quark also plays a huge role in Higgs boson production.

“Much of what we think we know about the Higgs boson hinges on its relationship with the top quark,” says Rachel Hyneman, a graduate student at the University of Michigan who worked on the ATLAS analysis. “We believe that roughly 90 percent of Higgs bosons are produced through virtual top quarks.”

The proton-proton collisions inside the LHC produce long chain reactions that often involve multiple steps and players. These new studies focused on the rare process in which two gluons inside the colliding protons fuse and produce two virtual top quarks, which are quantum mechanical fluctuations and not yet fully formed discrete particles.

“When these nascent top quarks recombine, they normally pop out a single Higgs boson,” Hyneman says. “But 1 percent of the time, this solitary Higgs is accompanied by two real top quarks. This is what we set out to find.”

Because Higgs bosons and top quarks are short-lived particles, they almost immediately transform into more-stable daughter particles, many of which also decay. This rapid transition from one generation to the next makes it challenging—though not impossible—to retrace the lineage of the detected daughter particles back to their common ancestor.

“We looked at many different decay modes of Higgs bosons,” says Chris Neu, a physicist at the University of Virginia who worked on the CMS analysis. “This process is so rare that we needed to combine results from different Higgs signatures to maximize our sensitivity and establish the top-Higgs signal.”

The next step is to precisely measure this coupling strength and determine if it matches the predictions.

"Directly measuring the coupling of the top quark to the Higgs boson is a fundamental test of the Standard Model,” says Sally Dawson, a senior physicist and theorist at DOE’s Brookhaven National Laboratory. “This measurement limits the possibilities for new heavy particles that may interact with the top quark."

Further studies will continue to explore the behavior of the Higgs boson and how it fits into the universal mosaic of matter.

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Approaching disability like a scientist

People with disabilities are underrepresented in STEM.

Collage of Stephen Hawking

When sociologist and broadcaster Tom Shakespeare was a graduate student at King’s College, Cambridge in the early 1990s, he sent a request to a physicist who was on his way to becoming the most famous scientist in modern history. 

Shakespeare was part of a group organizing a campaign to raise awareness about the need for better access for students with disabilities. And he wanted Stephen Hawking in on it. 

“We wrote to him and said, ‘Would you support us?’” Shakespeare says. “And he did.”

Hawking, who died on March 14, is known for many things: his groundbreaking theories about black holes, his gift for communicating science to the public, his bestselling books and television appearances. He was also one of the longest-surviving patients with amyotrophic lateral sclerosis (ALS), living with the neurodegenerative disease for more than 50 years. 

The combination made him famous and something of an ambassador for the 1 billion people on the planet living with some form of disability. He demonstrated the complexity and individuality of disability, while shattering misconceptions about the levels at which people with disabilities can contribute to society. 

But despite his decades of living and working in the public eye, scientists with disabilities are still fighting to be counted equally in academia and to get the access they need to fulfill their potential. 

“Hawking's example had great impact on many people,” says Aaron Schaal, a mathematical physicist who, like Hawking, uses a wheelchair and communicates largely via computer. “He showed non-disabled people that disability need not have any influence on one’s mind. However, there are still many prejudices regarding academics with disabilities.”

Collage of Claire Malone
Artwork by Sandbox Studio, Chicago

Opening doors

Hawking relied on round-the-clock assistance from a team of aids; a wheelchair equipped with state-of-the-art technology and voice synthesizers; and personalized accommodations in his home and places of work. “I realize that I am very lucky, in many ways,” Hawking wrote in an introduction to the World Health Organization’s first and only report on the global status of people with disabilities. “My success in theoretical physics has ensured that I am supported to live a worthwhile life. It is very clear that the majority of people with disabilities in the world have an extremely difficult time with everyday survival, let alone productive employment and personal fulfillment.”

According to a 2017 National Science Foundation report, 12.6 percent of the US population—approximately 40 million people—has some form of disability. But they are underrepresented in science: People with disabilities make up only 8.6 percent of employed scientists and engineers and 6.1 percent of physicists. This is despite that fact that undergraduates with disabilities enroll in STEM majors at roughly the same rate—about one in four—as those without. 

And while only 3.6 percent of non-disabled people in science and engineering cite illness or disability as reason for not working, 34 percent of people with disabilities do, indicating that disability is still a significant barrier to employment. 

When physicist Claire Malone finished her master’s degree in 2014, she decided to do her PhD research at the University of Cambridge, with a long-term placement at CERN, the largest particle physics laboratory in the world. Malone has cerebral palsy, which affects her movements, speech and the use of her hands. She uses a wheelchair to get around and a computer to help her communicate. 

She says she found CERN to be very accommodating, but there were still limitations that made her work more difficult. Her off-site accommodation had a door she could not open from the inside without assistance, and while she had an accessible office to work in on-site, she couldn’t reach much of the lab’s campus.

“I had a great room for me and my scribe to work in, but the rest of the site was pretty inaccessible,” Malone says. “So I was physically isolated from colleagues and missed out on some of the team interaction and exchange of ideas. I guess that is the trouble with [CERN’s] good old 1950s architecture.”

Physical accessibility is not the only issue. Born with limited sight, physicist John Gardner lost his vision entirely at 49 after what should have been a simple eye procedure. Throughout his career, he encountered numerous obstacles. For example, a commonly used tool in physics is an oscilloscope, which measures electrical signals over time. But oscilloscopes display these signals visually in a chart, which is essentially useless if you can’t see. 

“There are things like laboratory instruments that are unnecessarily inaccessible,” Gardner says. “It makes it hard for a blind person to do lab experiments that they’re otherwise perfectly capable of doing.” 

Graphical information is so crucial, and so entirely inaccessible for blind people, that Gardner founded a company to create tactile graphs, eventually retiring from physics to focus on the mission. Gardner, in other words, approached his exclusion from science by doing what scientists do best: creating solutions to seemingly impossible problems. 

Malone, too, devised workarounds to her challenges. “I think the biggest difficulty I have had to overcome in my physics studies is not being able to pick up a pencil and quickly scribble down a calculation,” she says. “Mathematics is the language of physics and most students develop an intuitive feel for how math ‘should work’ by ‘playing’ with equations on the page.” To make up for this, she developed a system of manipulating equations in her mind’s eye.

And Schaal, now a mathematical physicist at Ludwig Maximilians University of Munich, invented a communication board when he was just 9. The Plexiglass board is covered with letters, numbers and mathematical symbols, which he looks at in sequence to spell out words and do math. 

Hawking himself had to constantly innovate: As both Schaal and Malone point out, his condition, unlike each of theirs, was progressive, meaning he needed to change his adaptations along with his changing body. But, as he demonstrated, day-to-day barriers need not impede a larger goal. 

“I can’t drive a car until self-driving cars come along,” Gardner says. “But that doesn’t keep me from getting from place A to place B.”

Collage of John Gardner
Artwork by Sandbox Studio, Chicago

Learning by doing

In his book “The Panda’s Thumb,” evolutionary biologist Stephen Jay Gould wrote, “I am, somehow, less interested in the weight and convolutions of Einstein’s brain than in the near certainty that people of equal talent have lived and died in cotton fields and sweatshops.” 

It’s a sentiment that resonates with many groups who have been marginalized—“the centuries of blind people who have wasted away in sheltered workshops, institutions and rocking chairs across the world,” as Louisiana Tech Director of the Institute on Blindness Edward Bell put it—and it’s a core element of Hawking’s legacy. 

“The point about Hawking is that he showed that if you do accommodate, you do include, you’re going to get great results,” Shakespeare says, “because disabled people have the same talent as everybody else, and sometimes more.”

The authors of the WHO report noted that the global economy suffers when 1 billion people, nearly 15 percent of the world’s population, are relegated to the sidelines. Productivity suffers and tax revenue is lost, and the effects increase exponentially as family members take time off to care for loved ones who can’t work. One Canadian study estimated the cost at 6.7 percent of the nation’s GDP, a loss of around $100 billion in US dollars annually.

Some institutions are working to improve this. CERN established an official diversity policy in 2014, building on a previous code of conduct that emphasizes respect in the workplace. The lab has instituted more options to work remotely, provides things like parking permits and online information about accessible paths, and frequently hosts talks, workshops and seminars on inclusivity. (Shakespeare spoke at CERN in 2013.)

The lab also recently began a project to create earmarked positions for students with disabilities as part of its internship program, to help the students develop necessary skills for employment while increasing diversity on the lab’s campus and in the broader pipeline of future scientists. 

“Disability is a development issue,” says CERN Diversity Analyst Ioanna Koutava. “Research shows that disability may increase the risk of poverty and poverty may increase the risk of disability. With these positions we hope to give an opportunity to candidates to come work in a leading scientific institution... and for us to increase the inclusiveness of the organization by increasing our exposure to individual situations.”

Hawking himself saw inclusivity as a necessary effort, writing in his introduction to the WHO report, “We have a moral duty to remove the barriers to participation, and to invest sufficient funding and expertise to unlock the vast potential of people with disabilities.”

Hawking, with perseverance, genius and bit of luck, lived his vast potential. He inspired untold millions, broke down barriers and changed minds about what is truly possible, both in the cosmos and here on Earth. 

“Many of us look to him as someone who showed what you could achieve,” Shakespeare says. “He, in return, was willing to be seen as a disabled person for the point of trying to get more people a better deal in society.”

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Game-changing neutrino experiments

This neutrino-watchers season preview will give you the rundown on what to expect to come out of neutrino research in the coming years.

Neutrino running from machine poparazzi

There’s a lot to look forward to in the world of neutrinos, tiny particles that are constantly streaming through us unnoticed. 

According to theorist Alexander Friedland of SLAC National Accelerator Laboratory, if you looked at the field of neutrino research 20 years ago, you wouldn’t recognize it compared to what it is now. “The developments have been absolutely remarkable,” he says. “It has evolved so much.”

Twenty years ago, in 1998, neutrinos exposed a shortcoming of the Standard Model of particle physics, scientists’ best explanation of the fundamental particles and forces that make up everything. According to the Standard Model, neutrinos should have no mass. But according to the observations of the Super-Kamiokande and then the Sudbury Neutrino Observatory experiments, they did. It was already known that they came in three types, but if they had mass this meant that they also shifted from one type to another as they flew along at nearly the speed of light.

Many mysteries remain about these particles with minuscule masses: Do neutrinos actually come in four types, as suggested by some experiments? What are the masses of neutrinos? Are neutrinos their own antiparticles? What can neutrinos tell us about the Standard Model, astrophysical phenomena and the formation of the universe?

Our current neutrino experiments have all gotten to a sort of midway point, says Lindley Winslow, a physicist at MIT. “We’re refueling and looking at the maps and figuring out our next steps into this really uncharted land,” she says. “It’s a little bit of a time to congratulate ourselves that we got to this point and then make the big push to the unknown.”

With Neutrino 2018, the XXVIII International Conference on Neutrino Physics and Astrophysics, right around the corner, we asked some neutrino experts for their quick takes on the roster of experiments going into this season and their predictions for upcoming victories in the field. Here’s what they had to say.

Chasing hidden flavors

Neutrinos are known to oscillate between three known types, or flavors, as they move through space: electron, muon and tau. But in 1995, physicists working on the Liquid Scintillator Neutrino Detector, or LSND, at Los Alamos National Laboratory stumbled upon clues that there may be an extra flavor hiding on the sidelines. They called it a “sterile neutrino,” a neutrino flavor that would not interact like the others.

Person chasing hidden flavors of neutrinos
Artwork by Sandbox Studio, Chicago with Corinne Mucha

“Neutrinos outnumber electrons, protons and neutrons in today’s universe by a factor of 10 billion,” says physicist Joshua Spitz of the University of Michigan. 

“Given this, it’s easy to see that the existence of a fourth type of neutrino, and corresponding mixing to the other three, would have significantly affected the evolution of the universe. Specifically, large scale structure, galaxy formation, dark matter, cosmic microwave background observables, and the creation and abundance of heavy elements could all be affected by the addition of a new type of neutrino.”

In the years since the LSND anomaly, physicists have been designing experiments geared towards chasing down this hidden flavor. In 2002, the MiniBooNE experiment began collecting data related to this at Fermi National Accelerator Laboratory. 

Results have thus far shown an excess of MiniBooNE events that is consistent with the LSND signal, but it isn’t clear how this fits into a model of sterile neutrinos. The co-spokespeople for MiniBooNE, Richard Van de Water and Rex Tayloe, plan to present updated results at Neutrino 2018 that will add significant new information.

“The results will provide new information and insights into the question of the LSND and MiniBooNE excesses, especially the question of the consistency of the two data sets indicating whether new physics such as sterile neutrinos, or other more complicated models, are at play,” Van de Water says.

In addition, new, more sensitive experiments are just starting to come online. MiniBooNE’s successor is an experiment called MicroBooNE; it is expected to release its first physics results in the coming year. MicroBooNE will eventually be joined at Fermilab by ICARUS and SBND, forming a suite of three detectors known as the Short-Baseline Neutrino Program. 

Beyond these accelerator-based experiments—which also include the Japan-based JSNS2—a number of radioactive-source and reactor-based experiments, including PROSPECT, STEREO, DANSS, CHANDLER and SOLID, are also working and hope to catch the theorized sterile neutrino sometime in the near future.

Tackling the mass ordering

Just as we know there are at least three different flavors of neutrinos, we also know that there are three different neutrino masses. But how these mass states are ordered is still a mystery. There are two possible ways neutrino mass states can be ordered: normal or inverted. Although many signs are pointing towards a normal ordering, the final call is still in review.

Tackling the mass ordering
Artwork by Sandbox Studio, Chicago with Corinne Mucha

Knowing whether neutrinos have a normal or inverted mass ordering can help scientists test other models of the universe, such as one in which the four forces of nature unite into one at high energies.

In contrast with the short-baseline experiments searching for sterile neutrinos, experiments tackling the question of mass ordering are built to go long. The two major long-baseline experiments in operation are the T2K experiment hosted by KEK accelerator laboratory, which monitors a beam of neutrinos traveling more than 180 miles across Japan, and NOvA hosted by Fermilab, which studies a beam that originates about 500 miles from the detector in the United States. Fermilab just completed an upgrade of its accelerators, and the detector for the T2K experiment will gain sensitivity with an upgrade this summer. Reactor-based experiments, such as the Daya Bay Reactor Neutrino Experiment in China, are also involved in the investigation.

Many of the experts consulted for this article—including André de Gouvêa at Northwestern and Friedland at SLAC—say they are looking forward to a slew of results in the next few years from NOvA and T2K that could bring us closer than ever to figuring out the mass ordering.

According to Spitz at Michigan, telescope-based observations of large-scale structure are also quickly gaining sensitivity to measuring the sum of the neutrino masses by looking at its influence on the gravitational clumping of matter in the early universe. Combining this with other results might allow scientists to uncover the neutrino mass ordering.

“Seeing agreement between NOvA, T2K and telescopic observations of this property of the neutrinos will be absolutely extraordinary,” he says, “and seeing disagreement might even be more interesting. This will truly be ‘astroparticle physics,’ when we can start relating the properties of the neutrino to the formation of the universe.”

Other experiments are working to measure the combined mass of the three types of neutrinos. KATRIN, a neutrino experiment in Germany with a 200-ton spectrometer at its core, has just started taking data. The experiment will measure the energy of the electrons spit out during the decay of the radioactive isotope tritium and look for very slight distortions that will clue researchers in to the neutrino’s absolute mass.

“The absolute neutrino mass is one of these things that oscillation experiments can’t see at all,” says Alexander Himmel, a physicist at Fermilab. “We’re seeing the very beginning of data-taking with KATRIN. It’s a very technically challenging experiment and it’s been slow to get up and running, so over the next few years we’re looking forward to getting really beautiful measurements from them, which I think will be very exciting.”

Project 8, another experiment going after the absolute mass of the neutrino, will also use tritium, instead measuring the energy of individual electrons by measuring the frequency of their spiraling motion in a magnetic field. Although the goal of Project 8 is to demonstrate the technology, physicists hope to scale up the technique in the future.

Blowing the whistle on neutrino fouls

Most of the particles in our universe have corresponding antiparticles, which carry equal but opposite charges of their partners. 

Referee blowing the whistle on neutrino fouls
Artwork by Sandbox Studio, Chicago with Corinne Mucha

Scientists believe that during the Big Bang, there should have been equal amounts of matter and antimatter in the universe. But when matter and antimatter collide, they annihilate. This match should have ended in a tie, with matter and antimatter cancelling each other out and leaving behind nothing but energy. 

And yet somehow, as you can guess from the matter-packed world we live in, matter was victorious. Scientists are still trying to figure out why. This is where charge-parity violations come into play. 

For a while, physicists believed there had to be some sort of symmetry between the behavior of particles and their antimatter teammates, called CP symmetry. This means that if antineutrinos subbed in for neutrinos, the universe should treat them identically. But if this symmetry is somehow broken, it might explain how matter got the upperhand.

Long-baseline experiments such as NOvA and T2K, with assistance from reactor-based experiments such as Daya Bay, have set out to track the oscillations of neutrinos and antineutrinos to determine if they are fundamentally different. That would indicate that CP is broken, offering a possible explanation for why matter took home the win in the creation of the universe.

According to Friedland, one of the major neutrino announcements expected soon is the release of antineutrino run data from the NOvA experiment, which, in combination with T2K, will either strengthen existing hints of CP violation or send teams of scientists running off in some new direction.

“We are seeing hints that something interesting is happening between neutrinos and antineutrinos,” says Kendall Mahn, a physicist at Michigan State University. “We’re trying to take more data to see if this is going to turn into something really exciting or fizzle out. It just shows us that we’re really on the leading edge of something.”

Another possible symmetry-breaking that might have had a hand in sculpting the universe as we know it is called lepton number violation. This would occur if neutrinos were actually their own antiparticles. Scientists are testing this hypothesis by looking for a process in which neutrinos act as their own opposites and cancel one another out: neutrinoless double-beta decay. 

Experiments such as CUORE, Majorana Demonstrator, GERDA and NEXT are on the offensive, all having recently published new results. Results from KamLAND-Zen 800 are also anticipated by the end of the year.

“Just turning the detector on was a feat in itself, says Winslow at MIT, referring to CUORE. “Now we have the hard job of keeping it running for five years and getting the ultimate sensitivity where we actually think we should be able to see something.”

The Standard Model fitness test

Scientists aren’t just studying neutrinos in neutrino experiments; they’re also creating tests of the Standard Model. Last summer, physicists involved in the COHERENT experiment hosted at Oak Ridge National Laboratory were able to measure for the first time a phenomenon predicted via the Standard Model that had been sought for four decades without detection. The phenomenon, known as coherent elastic neutrino-nucleus scattering, also comes into play in the explosions of supernovae. 

Neutrinos lifting weights in the gym, the Standard Model fitness test
Artwork by Sandbox Studio, Chicago with Corinne Mucha

In coherent elastic neutrino-nucleus scattering, a neutrino hitting the nucleus of an atom does not just hit one part of it—a proton or a neutron—but rather kicks the entire nucleus as a whole.

“It’s like hitting a bowling ball with a ping pong ball,” says Kate Scholberg, a physicist at Duke. “Neutrinos almost never interact, but this cross-section is so large that the probability of a collision is 100 times more than for a regular neutrino interaction. The problem is that when you hit a bowling ball with a ping pong ball, it’s hard to get the bowling ball rolling very fast, there’s a really low-energy recoil [that is difficult to observe].” 

Over the next few months, COHERENT, which currently holds the title of world’s smallest neutrino detector, will continue publishing results, searching for this effect in different nuclei, eventually leading to larger detectors capable of searching for additional oscillation effects.

Taking different approaches is key in propelling neutrino research forward, says Janet Conrad, a physicist at MIT. Another instrument she’s looking forward to using for precision measurements that test the Standard Model is IceCube, the giant South Pole neutrino observatory that consists of a cubic kilometer of Antarctic ice. 

“IceCube is a unique detector that has produced nice dark matter results and a really interesting sterile neutrino limit,” she says, “but I think what many people don’t realize is what a fantastic beyond-Standard-Model search detector IceCube actually is. And it's just getting better as we understand the detectors more and more. Within the particle physics community, IceCube is the dark horse running up next to us that we haven't yet recognized.”

The wild card

When a massive star explodes, the first messengers it sends across the galaxy are its speedy, unhindered neutrinos. Because these neutrinos escape from the star’s collapsing core, they contain information about the early stages of supernova events that is not available in any other way.

People playing catch in a field
Artwork by Sandbox Studio, Chicago with Corinne Mucha

In 1987, Supernova 1987A exploded in a nearby galaxy. Kamiokande-II, the Irvine-Michigan-Brookhaven detector and the Baksan Neutrino Observatory each recorded a burst of neutrino events from the explosion. The detections allowed scientists to confirm theoretical models of what goes on in the heart of these violent stellar explosions.

Although we’re not sure when the next galactic supernova will go off, the idea that it could happen in the coming decades—during a time where there are a growing number of neutrino experiments in operation—is exciting to many, including Scholberg and Friedland. 

“The rate of supernova explosions is estimated to be two to three per century in our galaxy,” says Friedland, “which is about the same rate as large earthquakes occurring in the Bay Area. In the case of supernovae, just as in the case of earthquakes, we don’t know if one will go off tomorrow, but it definitely pays to be prepared.”

At the moment, Scholberg says, seven large neutrino detectors could observe a galactic supernova, and more will join them in the coming years. Seeing a nearby supernova would allow us to pursue many detailed questions about distant astrophysical phenomena, which will better inform our theories of the universe.

Going into overtime

Before the end of this decade, additional experiments such as JUNO, an underground observatory in China that will build on the successes of the Daya Bay reactor experiment, will come online. 

Crowd of people in the stands of a game, one woman holding sign that says
Artwork by Sandbox Studio, Chicago with Corinne Mucha

In the next 10 to 15 years, experiments will continue to grow and improve. The Fermilab-hosted Deep Underground Neutrino Experiment, DUNE, will send neutrinos racing more than 800 miles across the United States to better understand their oscillations and potentially definitively answer some of our current questions. 

Each question scientists answer is tied to other questions, and every point scored brings physicists ever closer to triumphs that could revolutionize our picture of the universe, from its tiniest particles to its largest scale astrophysical phenomena.

“Every day I come into work and we take a little step forward to some new understanding,” Mahn says. “There’s more stuff out there and we’re getting closer to it.”

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The personal side of science

The Story Collider visits Fermilab to highlight true stories from scientists.

The storytellers of Story Collider gather on stage

How do snails, shooting stars and science fiction books all relate to physics? They’re just a few examples of where Fermilab scientists and other guest speakers drew inspiration for a recent edition of The Story Collider.

“Stories underlie a lot of what we do as scientists, whether we know it or not,” says Cindy Joe, a Fermilab engineering physicist. “We have a lot of beautiful stories, both science-related and not, but as scientists we sometimes pretend we’re above the emotional part of what we do. But it’s okay for emotion to underlie it.”

The Story Collider features storytellers in podcasts and live shows across the country—everyone from comedians and doctors to poets and physicists. It aspires to humanize its speakers and show that at the basis of every profession, including the sciences, is a person with hopes, dreams, desires and struggles.

On May 12, The Story Collider visited Fermilab with hosts Erin Barker and Kellie Vinal to explore some personal stories from people affiliated with lab. It was the culmination of the spring season of the Fermilab Arts and Lecture Series, which organizes and hosts events like concerts, theater productions and public lectures at the lab.

The evening saw both laughter and tears. Joe told the story of her pet snail who helped her through difficult times at the beginning of her physics career, when she often felt overlooked and ignored. But caring for a small, often overlooked and non-traditional pet helped Joe realize her worth as a person and a scientist.

“I realized that my core belief that every single person had fundamental, inherent value should maybe also apply to myself,” she said. “That my different perspective was important. That my experiences were real. That my contributions were good. That I deserved no less gentle kindness and consideration than anyone else. And maybe I should treat myself like it.”

Don Lincoln, Fermilab senior scientist and book author, told the audience about an accomplishment he is especially proud of: inspiring a young woman to pursue the sciences through his writing. He emphasized that writing popular science books for a general audience is a crucial method of inspiring young scientists.

“There was someone out there— someone who had the ability and passion to learn but didn’t even know that a career in physics existed,” he said.

Fermilab scientist emeritus Mike Albrow painted a picture of the night sky for his audience. The same night sky stirred him as both a child and adult, always creating, “a feeling of being all alone in the vast emptiness of it all.” He told the audience how much of a detriment light pollution was to the night sky and for kids (and adults) who wanted to look at the stars.

Visual artist and first-ever Fermilab artist-in-residence Lindsay Olson walked the audience through intermingling science and art—and how she fell in love with science in the middle of a waste water treatment plant. At Fermilab, despite feeling intimidated by high-energy physics, she relied on her curiosity to explore and then show through her art that you don’t need a PhD to be fascinated by physics.

Finally, Fermilab senior scientist Herman White described when a small and coincidental connection—his roots in Alabama—became a way for him to connect to people and share his science with them.

“Especially now, it’s incredibly important to connect the public to science and change their perception of it,” White says. “We need to relate to people on a human level.”

Joe notes that many scientists aren’t used to telling stories, but their stories are an opportunity both to convey the value of science and create relationships with people outside of the field. She highlights that science is part of everyone’s life, no matter where they come from or what they do for a living.

“The underlying theme is that science is human," she says. "We can all tell stories about science, no matter its role in our lives, by sharing our feelings, thoughts, and background. And our stories as scientists are really just our stories as humans.”

The Story Collider at Fermilab

Video of The Story Collider at Fermilab
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