- Press Release Distribution

Field guides: Argonne scientists bolster evidence of new physics in Muon g-2 experiment

Field guides: Argonne scientists bolster evidence of new physics in Muon g-2 experiment
( Scientists are testing our fundamental understanding of the universe, and there's much more to discover.

What do touch screens, radiation therapy and shrink wrap have in common? They were all made possible by particle physics research. Discoveries of how the universe works at the smallest scale often lead to huge advances in technology we use every day.

Scientists from the U.S. Department of Energy's (DOE) Argonne National Laboratory and Fermi National Accelerator Laboratory, along with collaborators from 46 other institutions and seven countries, are conducting an experiment to put our current understanding of the universe to the test. The first result points to the existence of undiscovered particles or forces. This new physics could help explain long-standing scientific mysteries, and the new insight adds to a storehouse of information that scientists can tap into when modeling our universe and developing new technologies.

"These findings could have major implications for future particle physics experiments and could lead to a stronger grasp on how the universe works." -- Ran Hong, Argonne postdoctoral appointee

The experiment, Muon g-2 (pronounced Muon g minus 2), follows one that began in the '90s at DOE's Brookhaven National Laboratory, in which scientists measured a magnetic property of a fundamental particle called the muon.

The Brookhaven experiment yielded a result that differed from the value predicted by the Standard Model, scientists' best description of the makeup and behavior of the universe yet. The new experiment is a recreation of Brookhaven's, built to challenge or affirm the discrepancy with higher precision.

The Standard Model very precisely predicts the muon's g-factor -- a value that tells scientists how this particle behaves in a magnetic field. This g-factor is known to be close to the value two, and the experiments measure their deviation from two, hence the name Muon g-2.

The experiment at Brookhaven indicated that g-2 differed from the theoretical prediction by a few parts per million. This miniscule difference hinted at the existence of unknown interactions between the muon and the magnetic field -- interactions that could involve new particles or forces.

The first result from the new experiment strongly agrees with Brookhaven's, strengthening the evidence that there is new physics to discover. The combined results from Fermilab and Brookhaven show a difference from the Standard Model at a significance of 4.2 sigma (or standard deviations), slightly less than the 5 sigma that scientists require to claim a discovery, but still compelling evidence of new physics. The chance that the results are a statistical fluctuation is about 1 in 40,000.

Particles beyond the Standard Model could help to explain puzzling phenomena in physics, such as the nature of dark matter, a mysterious and pervasive substance that physicists know exists but have yet to detect.

"This is an incredibly exciting result," said Argonne's Ran Hong, a postdoctoral appointee who worked on the Muon g-2 experiment for over four years. "These findings could have major implications for future particle physics experiments and could lead to a stronger grasp on how the universe works."

The Argonne team of scientists contributed significantly to the success of the experiment. The original team, assembled and led by physicist Peter Winter, included Argonne's Hong and Simon Corrodi, as well as Suvarna Ramachandran and Joe Grange, who have since left Argonne.

"This team has an impressive and unique skill set with high expertise regarding hardware, operational planning and data analysis," said Winter, who leads the Muon g-2 contributions from Argonne. "They made vital contributions to the experiment, and we could not have obtained these results without their work."

To derive the muon's true g-2, the scientists at Fermilab produce beams of muons that travel in a circle through a large, hollow ring in the presence of a strong magnetic field. This field keeps the muons in the ring and causes the direction of a muon's spin to rotate. The rotation, which scientists call precession, is similar to the rotation of earth's axis, only much, much faster.

To calculate g-2 to the desired precision, the scientists need to measure two values with very high certainty. One is the rate of the muon's spin precession as it traverses the ring. The other is the strength of the magnetic field surrounding the muon, which influences its precession. That's where Argonne comes in.

Field trip Although the muons travel through an impressively constant magnetic field, ambient temperature changes and effects from the experiment's hardware cause slight variations throughout the ring. Even these small shifts in field strength, if not accounted for, can significantly impact the accuracy of the g-2 calculation.

In order to correct for the field variations, the scientists constantly measure the drifting field using hundreds of probes mounted to the walls of the ring. In addition, they send a trolley around the ring every three days to measure the field strength where the muon beam actually passes through. Mounted on the trolley are probes that map out the magnetic field with incredibly high precision throughout the ring's 45-meter circumference.

To reach the ultimate uncertainty goal of less than 70 parts per billion (around 2.5 times better than the field measurement in the previous experiment), Argonne scientists refurbished the trolley system used in the Brookhaven experiment with advanced communication abilities and new, ultraprecise magnetic field probes developed by the University of Washington.

The trolley goes around the ring in both directions, taking around 9,000 measurements per probe and direction. The scientists use the measurements to reconstruct slices of the magnetic field and then derive a full, 3D map of the field in the ring. Field values at points on the map go into the g-2 calculation for muons passing through those locations. The better the field measurements, the more meaningful the final result.

The scientists also converted some of the analog signals used in the old experiment into digital signals to increase the amount of data they could obtain from the probes. This required complex engineering of the trolley's communications system to minimize disturbances to the sensitive probing mechanisms.

"It was quite challenging to make the trolley operate smoothly and safely. It required the control system to handle routine operations but also identify emergencies and react appropriately," said Hong, whose background in both scientific research and engineering was crucial for designing the trolley to operate with limited disruption to the experiment.

The team plans to upgrade the trolley system for the next data taking period to further improve the measurements by reducing the uncertainty bit by bit.

Fine tuning In precision experiments like Muon g-2, the main objective is to reduce any systematic uncertainty or error that could affect the measurements.

"Measuring the raw numbers is relatively easy -- figuring out how well we know the numbers is the real challenge," said Corrodi, a postdoctoral appointee in Argonne's High Energy Physics division (HEP).

To ensure the accuracy of the magnetic field measurements, the scientists calibrated the probes using Argonne's 4-Tesla Solenoid Facility, which houses a magnet from a former magnetic resonance imaging (MRI) scanner. The magnet produces a uniform and stable magnetic field with over 400 times the strength of a refrigerator magnet.

Argonne scientists calibrated the probes in the trolley against readings from a probe that was designed and tested inside the solenoid magnet. This process ensures the probes each read the same measurement when in the same magnetic field and enables the scientists to make accurate corrections. The test facility allowed the scientists to achieve field measurements down to several parts per billion -- like measuring the volume of water in a swimming pool down to the drop.

"In addition to calibrating the probes, we improved the field measurements by adjusting operation settings on the fly," said Corrodi, "During data analysis, we found some effects we did not expect."

When Corrodi and team saw glitches in the data, they investigated the system to pinpoint the cause. For example, certain devices in the ring focus the muon beam to keep it centered. These devices, however, slightly disrupt the magnetic field in the ring. The scientists designed a way to measure this effect in order to remove it from the analysis.

To view related video, click here.

Putting it all together The journey of the magnetic field data from probe to computer is complex. Corrodi, Hong and others configured the hardware and software to read the data from the field probes with the correct time and location stamps. They also had to make sense of the data, which start out in binary code, in order to integrate them with the common analysis framework for the experiment.

"We had to convert the raw data into something we could work with," said Hong, "and we were in charge of the data quality control, determining what flawed data to discard in the ultimate g-2 analysis."

Corrodi will lead the analysis team for the magnetic field, resolving conflicts with equipment and making sure the various teams in the experiment converge on the next result, said Winter. "You really need to understand the entire field analysis in order to reach our scientific goals."

The future of muon experiments The first thing the scientists plan to do is to double-check the results.

"So far, the precision of the ultimate g-2 measurement is comparable to that of the Brookhaven experiment, but that is dominated by the fact that the data are limited so far," said Corrodi. "We have only analyzed 6% of the data we plan to take over the entire experiment. Those added data will reduce the uncertainty significantly."

The first result is also encouraging to scientists conducting other present and planned muon experiments, including a future g-2 experiment that will be conducted in Japan, and the next muon experiment at Fermilab -- the Mu2e experiment. These projects are already using Argonne's Solenoid Facility to cross-calibrate their magnetic field probes with the ones used at Fermilab.

"There could be a renewed effort to look for muons at the Large Hadron Collider, searching for possible hints of the new physics behind the g-2 value," said Carlos Wagner, a theoretical physicist in Argonne's HEP, who works to try to explain these phenomena. "There could also be renewed interest in the construction of a muon collider, which could provide a direct way of checking this new physics."

Once scientists get a handle on this new physics, it may be able to inform cosmological and quantum mechanical models, or even help scientists to invent new technologies down the road -- the next shrink wrap, perhaps.


The collaboration published a paper on the result in Physical Review Letters, titled "Measurement of the positive muon anomalous magnetic moment to 0.46 ppm." A paper on the magnetic field measurement was also published in Physical Review A, titled "Magnetic-field measurement and analysis for the Muon g - 2 Experiment at Fermilab."

The work on Muon g-2 at Argonne is funded by DOE's Office of Science, High Energy Physics.

About Argonne's Center for Nanoscale MaterialsThe Center for Nanoscale Materials is one of the five DOE Nanoscale Science Research Centers, premier national user facilities for interdisciplinary research at the nanoscale supported by the DOE Office of Science. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE's Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge, Sandia and Los Alamos National Laboratories. For more information about the DOE NSRCs, please visit

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.

The U.S. Department of Energy's Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit

[Attachments] See images for this press release:
Field guides: Argonne scientists bolster evidence of new physics in Muon g-2 experiment


First results from Fermilab's Muon g-2 experiment strengthen evidence of new physics

First results from Fermilabs Muon g-2 experiment strengthen evidence of new physics
AMHERST Mass. - The long-awaited first results from the Muon g-2 experiment at the U.S. Department of Energy's Fermi National Accelerator Laboratory show fundamental particles called muons behaving in a way that is not predicted by scientists' best theory, the Standard Model of particle physics. This landmark result, made with unprecedented precision and to which UMass Amherst's David Kawall's research group made key contributions, confirms a discrepancy that has been gnawing at researchers for decades. "Today is an extraordinary day, long awaited ...

Surgical sutures inspired by human tendons

Surgical sutures inspired by human tendons
Sutures are used to close wounds and speed up the natural healing process, but they can also complicate matters by causing damage to soft tissues with their stiff fibers. To remedy the problem, researchers from Montreal have developed innovative tough gel sheathed (TGS) sutures inspired by the human tendon. These next-generation sutures contain a slippery, yet tough gel envelop, imitating the structure of soft connective tissues. In putting the TGS sutures to the test, the researchers found that the nearly frictionless gel surface mitigated the damage typically ...

Research brief: Reflecting sunlight could cool the Earth's ecosystem

Published in the Proceedings of National Academy of Sciences, researchers in the Climate Intervention Biology Working Group -- including Jessica Hellmann from the University of Minnesota Institute on the Environment -- explored the effect of solar climate interventions on ecology. Composed of climate scientists and ecologists from leading research universities internationally, the team found that more research is needed to understand the ecological impacts of solar radiation modification (SRM) technologies that reflect small amounts of sunlight back into space. The team focused on a specific proposed SRM strategy -- referred ...

Race and poverty appear to guide heart muscle DNA methylation in heart-failure patients

Race and poverty appear to guide heart muscle DNA methylation in heart-failure patients
BIRMINGHAM, Ala. - Race associates with the risk of death from end-stage heart failure. So, identifying the molecular determinants of that risk may help the pursuit of the novel diagnosis and prognosis of heart failure, and its therapy. A University of Alabama at Birmingham study of end-stage heart-failure patients has found that cytosine-p-guanine, or CpG, methylation of the DNA in the heart has a bimodal distribution among the patients, and that race -- African American versus Caucasian -- was the sole variable in patient records that explained the difference. A subsequent ...

Parkinson's discovery points to possible future treatment approaches

Parkinsons discovery points to possible future treatment approaches
More than 20 years after the discovery of the parkin gene linked to young-onset Parkinson's disease, researchers at The Ottawa Hospital and the University of Ottawa may have finally figured out how this mysterious gene protects the brain. Using human and mouse brain samples and engineered cells, they found that the parkin protein works in two ways. First, it acts like a powerful antioxidant that disarms potentially harmful oxidants in the brain, including dopamine radicals. Second, as the brain ages and dopamine radicals continue to build up, parkin sequesters these harmful molecules in a special storage site within vulnerable nerve cells, so they can continue to ...

Why our brains miss opportunities to improve through subtraction

Why our brains miss opportunities to improve through subtraction
CHARLOTTESVILLE, Va. -- If, as the saying goes, less is more, why do we humans overdo so much? In a new paper featured on the cover of Nature, University of Virginia researchers explain why people rarely look at a situation, object or idea that needs improving -- in all kinds of contexts -- and think to remove something as a solution. Instead, we almost always add some element, whether it helps or not. The team's findings suggest a fundamental reason that people struggle with overwhelming schedules, that institutions bog down in proliferating red tape, and, of particular ...

Predicting COVID-19 outbreaks with cell phone mobility data

Mobility tracking using cell phone data showing greater movement of people is a strong predictor of increased rates of COVID-19, according to new data in CMAJ (Canadian Medical Association Journal). "This study shows that mobility strongly predicts [severe acute respiratory syndrome coronavirus 2] SARS-CoV-2 growth rate up to 3 weeks in the future, and that stringent measures will continue to be necessary through spring 2021 in Canada," writes Dr. Kevin Brown, Public Health Ontario, with coauthors. Until Canadians are widely vaccinated against SARS-CoV-2, nonpharmaceutical public health interventions such as physical distancing and limiting social contact will be the main population-based means of controlling the spread of the virus. "Mobility ...

Genome sequencing reveals a new species of bumblebee

Genome sequencing reveals a new species of bumblebee
While studying genetic diversity in bumblebees in the Rocky Mountains, USA, researchers from Uppsala University discovered a new species. They named it Bombus incognitus and present their findings in the journal Molecular Biology and Evolution. Bumblebees are vital for agriculture and the natural world due to their role in plant pollination. There are more than 250 species of bumblebee, and they are found mainly in northern temperate regions of the planet. Alarmingly, many species are declining due to the effects of climate change, and those with alpine and arctic habitats are particularly threatened. However, the full diversity of bumblebee ...

New biosensor makes control hormone auxin visible in cells

New biosensor makes control hormone auxin visible in cells
The hormone auxin is of central importance for the development of plants. Scientists at the University of Bayreuth and the Max Planck Institute for Developmental Biology in Tübingen have now developed a novel sensor that makes the spatial distribution of auxin in the cells of living plants visible in real time. The sensor opens up completely new insights into the inner workings of plants for researchers. Moreover, the influences of changing environmental conditions on growth can now also be quickly detected. The team presents its research results in the journal Nature. The effects of the plant hormone auxin were first described ...

Ant responses to social isolation resemble those of humans

Ant responses to social isolation resemble those of humans
Ants react to social isolation in a similar way as do humans and other social mammals. A study by an Israeli-German research team has revealed alterations to the social and hygienic behavior of ants that had been isolated from their group. The research team was particularly surprised by the fact that immune and stress genes were downregulated in the brains of the isolated ants. "This makes the immune system less efficient, a phenomenon that is also apparent in socially isolating humans - notably at present during the COVID-19 crisis," said Professor Susanne Foitzik, who headed up the study at Johannes ...


Scientists model 'true prevalence' of COVID-19 throughout pandemic

New breakthrough to help immune systems in the fight against cancer

Through the thin-film glass, researchers spot a new liquid phase

Administering opioids to pregnant mice alters behavior and gene expression in offspring

Brain's 'memory center' needed to recognize image sequences but not single sights

Safety of second dose of mRNA COVID-19 vaccines after first-dose allergic reactions

Changes in disparities in access to care, health after Medicare eligibility

Use of high-risk medications among lonely older adults

65+ and lonely? Don't talk to your doctor about another prescription

Exosome formulation developed to deliver antibodies for choroidal neovascularization therapy

Second COVID-19 mRNA vaccine dose found safe following allergic reactions to first dose

Plant root-associated bacteria preferentially colonize their native host-plant roots

Rare inherited variants in previously unsuspected genes may confer significant risk for autism

International experts call for a unified public health response to NAFLD and NASH epidemic

International collaboration of scientists rewrite the rulebook of flowering plant genetics

Improving air quality reduces dementia risk, multiple studies suggest

Misplaced trust: When trust in science fosters pseudoscience

Two types of blood pressure meds prevent heart events equally, but side effects differ

New statement provides path to include ethnicity, ancestry, race in genomic research

Among effective antihypertensive drugs, less popular choice is slightly safer

Juicy past of favorite Okinawan fruit revealed

Anticipate a resurgence of respiratory viruses in young children

Anxiety, depression, burnout rising as college students prepare to return to campus

Goal-setting and positive parent-child relationships reduce risk of youth vaping

New research identifies cancer types with little survival improvements in adolescents and young adul

Oncotarget: Replication-stress sensitivity in breast cancer cells

Oncotarget: TERT and its binding protein: overexpression of GABPA/B in gliomas

Development of a novel technology to check body temperature with smartphone camera

The mechanics of puncture finally explained

Extreme heat, dry summers main cause of tree death in Colorado's subalpine forests

[] Field guides: Argonne scientists bolster evidence of new physics in Muon g-2 experiment