Newswise — When astronomers point their telescopes to the heavens, they tend to look toward the light. They may search for the pin pricks of shining stars, the billowing of cold gas clouds, the faint heat of a star nursery or the rhythmic blaze of a pulsar. These faint signals of light beckon in a universe that is mostly dark.

In fact, the visible bits only account for 5% of the universe, while the dark side makes up the other 95%.

Now, an ongoing experiment at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility is aiming a spotlight into this so-called hidden dark sector. It aims to uncover hints of particles that interact with the dark by catching their light. 

“You underestimate the power of the dark side.”

Most of our universe is currently thought to be composed of dark matter and dark energy. While the dark sector isn’t visible to light microscopes, its existence is inferred by how it affects the stars and galaxies we study.

Currently, it’s thought that fully 27% of our universe is dark matter. This is matter that, as far as we know, isn’t made of the ordinary particles found in the Standard Model, the theoretical framework that nuclear physicists use to describe the subatomic particles that build our visible universe, such as protons and neutrons.

According to Liping Gan, the Jefferson Lab Eta Factory (JEF) experiment aims to capture hints of particles that connect the light and dark sides. Gan is a professor at the University of North Carolina, Wilmington, and a spokesperson for the JEF experiment. She says one of the goals of the experiment is to produce and capture hints of dark matter particles.

“One of the first ones is to search for dark gauge bosons. And that will give us some clue about the properties of the dark sector,” she said. 

If they do exist, dark gauge bosons would be rare examples of particles that can interact with the ordinary particles described in the Standard Model, as well as the mysterious dark matter particles.

To search for these bosons, ironically, the physicists will be looking for faint signals of light. 

“There’s no such thing as ‘the unknown’, only things temporarily hidden, temporarily not understood.”

The experiment will be carried out with the Continuous Electron Beam Accelerator Facility, a DOE Office of Science user facility accessed by more than 1,700 nuclear physicists worldwide to study the nature of matter.

The original GlueX Forward Calorimeter, as installed in Jefferson Lab’s Experimental Hall D. (Aileen Devlin / Jefferson Lab)

In the experiment, the CEBAF accelerator will generate a beam of energetic electrons and direct them into a diamond crystal. There, the electrons stimulate the diamond to release highly energetic light particles, or photons. These tiny but mighty particles of light then barrel into a target made of hydrogen. 

Hydrogen atoms are the simplest element to explore: a single proton makes up the atom’s nucleus, while the motion of a single electron forms the atom’s outer perimeter. The interactions of those photons with hydrogen’s protons spawn additional particles that will then enter detectors, where many of them can be measured.

JEF experimenters are most interested in producing the eta (η) meson. Like the proton, the η meson is made of a combination of smaller particles called quarks and gluons. But unlike the proton, the η isn’t stable. Instead, it will fall apart, or decay, into other particles in about half of an attosecond (5×10-19 seconds).

“Then our goal becomes looking for a decay. There are very many different decay channels we are going to measure, because a different decay channel tells us a different part of the physics,” explained Gan. 

According to Simon Taylor, a Jefferson Lab staff scientist and spokesperson for the JEF experiment, the experimenters are looking for rare decays.

“And a particular rare decay that we’ve been focusing on is a four-photon final state,” he said. 

“Only 18 out of 10,000 will decay to this. Most of the etas will decay into two gammas. So that’s why we call it rare reaction or rare decays, it happens only for a small fraction of the experiment,” Gan said.

The most interesting decay channels in this experiment are when η may produce a dark gauge boson. Dark gauge bosons are thought to be both exceedingly rare and short-lived. They, too, will decay away into other particles in the tiniest of fractions of a second. 

“These other particles include photons of light. We don’t know if these dark gauge bosons exist or will be produced in these decays, but this decay mode will allow us to search for them,” said Taylor.

The researchers will sift through the data they collect to see if they can discover unexpected peaks in their data, where there are more four-photon groupings than they expect. This will trigger intensive analysis to determine if each of these “bumps” is a tell-tale sign of the η meson decay.

Justin Stevens is the Wilson & Martha Claiborne Stephens associate professor of physics at William & Mary and spokesperson for phase two of the Gluonic Excitations Experiment (GlueX-II). The JEF and GlueX-II experiments are running concurrently using the same apparatus. He explained that one of the biggest challenges the two experiments face is finding those tell-tale bumps of interest inside the ginormous amount of data that will be generated. 

For context, 50 million light photons slam into the hydrogen target every second during the run. Each one has the potential to generate a few to dozens of particles that will stream into the detectors, all at once.

“We are getting something like 5 to 10 times higher luminosity in total compared to the original phase of GlueX,” Stevens said.

Taylor said that there are also other issues that will make finding a rare bump a challenge.

“It can get confused with other reactions,” Taylor explained. “Photons are detected by reconstructing the electromagnetic showers they produce in a calorimeter.  Some tiny fraction of the time, one or more of the photons disappear down the beam line or in a hole in the detector. Or two very close showers of particles may merge in the calorimeter together.”

To ensure the researchers would be able to capture these rare reactions, they needed to optimize one of their main detectors. An upgrade would ensure the detector can measure the photons it catches to such accuracy, the physicists could be sure they are capturing signals from a potential dark gauge boson and not from the remnants of incoming photons or from other reactions.

“You can’t stop the signal, Mal. Everything goes somewhere.”

For this experiment, the JEF collaboration upgraded the existing GlueX Forward Calorimeter (FCAL) to improve its resolution and hardiness. 

A view of the FCAL system during the upgrade. (Aileen Devlin / Jefferson Lab)

FCAL originally consisted of 2,800 lead glass scintillating modules connected to photomultiplier tubes. Each module has a 4 cm square face to collect the incoming particles produced in the experiment. These modules were designed to capture incoming particles and convert them into showers of light as the particles travel down their 45 cm length. This light can then be measured by the photomultiplier tubes and converted into signals that are recorded as data.

The upgrade removed 440 of the lead glass modules at the center of the detector and replaced them with 1,596 smaller lead tungstate (PbWO4) crystals. The new crystals feature only a 2 cm square face and extend 20 cm in length. They form a central square inside the new Eta Calorimeter (ECAL) that is surrounded by 2,360 of the original lead glass modules. 

A lead glass scintillating module (left) with a lead tungstate (PbWO4) crystal (right) are shown here inside Experimental Hall D. (Aileen Devlin / Jefferson Lab)

Zisis Papandreou is a JEF experiment spokesperson and a professor and head of the physics department at the University of Regina in Saskatchewan Canada. He compared the upgraded detector to a digital camera.

“Essentially, we’re reconstructing something akin to an image. If you have a larger number of smaller pixels, you can improve the resolution in the image,” he said.

The new lead tungstate crystals are also radiation-hard, which means they can better withstand the onslaught of particles generated in experiments than the original lead glass modules. Centering the new crystal modules closest to the target allows them to take the brunt of the onslaught, protecting the lead glass modules from the highest-energy particles and resulting in a longer overall detector lifetime.

Funded by the lab, the Department of Energy and the National Science Foundation, the upgrade of FCAL to ECAL cost about $5 million. Several work groups at the lab also contributed to the upgrade, including the Radiation Detector & Imaging group, the Detector Support group, the Radiation Control Department, and the Fast Electronics group. 

After four years of R&D, the full-scale upgrade took about three years to complete, beginning in 2022 and wrapping up in early 2025. According to Alexander Somov, a staff scientist at Jefferson Lab and a spokesperson for the JEF experiment who led the ECAL construction, the detector has already proven its versatility.

“It is the largest lead-tungstate crystal calorimeter in the U.S., and it’s been successfully commissioned and integrated,” said Somov. “It took a few weeks to commission, and all modules are operational. It was working fine for the first run of approximately five months.”

ECAL was successfully commissioned in April 2025, with data acquired for JEF and GlueX-II in late spring and summer 2025. So far, the detector has collected about 75 days of data as counted by the Program Advisory Committee for the two experiments.

“And the first results we’re getting show that the performance of ECAL is in good agreement with our basic expectations. But there’s more analysis to come,” said Somov.

University of North Carolina Wilmington (UNCW) Physics Professor Liping Gan, George Washington University undergraduate student Olivia Nippe-Jeakins, UNCW undergraduate students Shane Whaley and Ben Simpson, Jefferson Lab Hall D Staff Scientist Alexander “Sasha” Somov, and UNCW postdoc Laveen Puthiya Veetil pose for a photo inside Jefferson Lab’s Experimental Hall D. (Aileen Devlin | Jefferson Lab)

The upgraded detector has also served as a training ground for undergraduate physics majors interested in pursuing a career in nuclear physics. In all, 28 undergraduate students from the JEF experiment’s 11 collaborating universities participated in ECAL fabrication, installation and commissioning. The project also involved three graduate students, six postdoctoral nuclear physicists and one visiting scientist. 

“These are valuable experiences to undergraduates and then later on, they go to graduate school and some of them already were talking about going to a university that has GlueX collaborators. So, the hardware work is an absolutely amazing experience for students,” said Papandreou.

“You built a time machine? Out of a DeLorean?”

The second and final run for these experiments is currently scheduled to resume this summer. In it, the collaborators also aim to collect data that may reveal new clues to our understanding of other phenomena, such as why matter beat out antimatter in the first second of the early universe.

George Washington University undergraduate Quinn Stefan, left, and graduate student Phoebe Sharp, right, monitor experiment progress inside the Experimental Hall D counting house at Jefferson Lab in Newport News, Va., on June 17, 2025. (Aileen Devlin | Jefferson Lab)

“For example, right now we see large asymmetry between matter and antimatter in the universe, and one of the goals is to search for maybe there’s some new symmetry violation beyond the Standard Model. The third goal is to understand why quantum chromodynamics (QCD) prevents quarks from being isolated via tests of fundamental symmetries at low energy,” Somov said.

Alongside these searches, the GlueX-II experiment collaborators are looking to expand their data on particles that include charm quarks, such as the J/ψ (J/psi) meson. While the more familiar protons and neutrons are made of up and down quarks, other subatomic particles include other quark flavors, such as the charm quark. These data offer a rare opportunity to look at in depth at how such particles are made.

“So that means we can do things like study J/ψ production with a lot higher statistics and look for the charm production mechanism with a lot more precision than we had before,” said Stevens.

As the collaborators prepare for their final data run, they have also already begun preparing for the next opportunity. The proposed GlueX-III run aims to increase the intensity of the photon beam. For GlueX, it achieved about 10 million photons per second, and GlueX-II has an intensity of about 50 million photons per second. The goal for GlueX-III is to slowly crank that up to around one hundred million photons per second.

“Once you understand the detector, you just drive up the rate,” Stevens said. “So, we’re going to keep pushing up the intensity as high as we can, because we just get more data. You can look at more rare decays, more rare processes.”

In the meantime, the collaborators have their hands full preparing for their next run this summer and are looking forward to what their data reveal about the light and dark sides of our universe.

Further Reading
GWU Research Magazine: The Particle Whisperers
UNCW: Undergraduates Step Into Physics Research
Technical Paper: Eta Decays with Emphasis on Rare Neutral Modes: The JLab Eta Factory (JEF) Experiment
Technical Paper: Update to the JEF proposal (PR12-14-004)
Technical Paper: Light monitoring system for the lead tungstate calorimeter in Hall D at Jefferson Lab

BYLINE: Michelle Alvarez

For Immediate Release_

March 23, 2026
Contact: Michelle Alvarez
malvarez@jlab.org

A Strong Case for Weak Interactions

Jefferson Lab physicist Ciprian Gal wins prestigious DOE award to search for cracks in physics’ best theory of the universe

Newswise — NEWPORT NEWS, VA – In fifth grade, Ciprian Gal received his physics textbook a year early. The book promised to explain everything, and young Gal believed it. “I was bragging to all my friends, look at this book. It tells you everything,” Gal said. “And I’m going to know everything about it.” Decades later, Gal, a staff scientist at the U.S. Department of Energy’s (DOE) Thomas Jefferson National Accelerator Facility, is still chasing answers. His work probing the fundamental forces that hold matter together earned him a DOE Office of Science Early Career Research Award. The five-year, $2.75 million award will fund personnel and research expenses related to Gal’s work on the Measurement of a Lepton-Lepton Electroweak Reaction (MOLLER) experiment. MOLLER aims to test whether the Standard Model of Particle Physics, scientists’ current best description of how particles interact, is actually complete. Measuring Weak Charge The Standard Model explains three of the four fundamental forces that govern the universe: electromagnetism, the strong force and the weak force. Gal’s research focuses on the measurement of the electron’s weak charge, a property that describes how electrons interact through the weak force. While physicists understand the weak force reasonably well, measuring its precise effects on electrons requires extraordinary precision. The MOLLER experiment will scatter electrons off other electrons in a hydrogen target. It will measure tiny differences in how they scatter depending on the electron’s spin direction. These differences are so tiny, estimated to be 35 parts per billion, that measuring them requires utmost accuracy and control over every aspect of the experiment. “It’s a precision measurement,” Gal said. “We need to know exactly what we’re measuring, down to very fine details.” The challenge extends beyond just taking measurements. Gal and his team must account for every possible source of uncertainty, from the quantum mechanics of how particles scatter to the precise geometry of their detector. Abhay Deshpande, who mentored Gal during his graduate studies at Stony Brook University and now collaborates with him on MOLLER, attributes this precision mindset to Gal’s fundamental approach to physics. “His penchant for precision and methodical approach makes him particularly suited to this exacting research,” said Deshpande, Brookhaven National Laboratory’s associate lab director for nuclear and particle physics and Stony Brook University distinguished professor of physics. The new measurements could indicate new particles or forces that physicists haven’t discovered yet. These deviations could help answer some of physics’ biggest mysteries: Why is there more matter than antimatter in the universe? What is dark matter made of? “Whether we confirm the Standard Model’s predictions or find something unexpected, this measurement will be a major step forward,” Gal said. “Either result will teach us something fundamental about how the universe works.” A Decade of Physics at Jefferson Lab Gal’s connection to Jefferson Lab began in 2014, long before he joined the staff. Immediately after earning his Ph.D., he came to the lab as a University of Virginia (UVA) postdoc, drawn by the facility’s unique capabilities for studying the internal structure of protons and neutrons. Over the next eight years, Gal worked at the lab through partnerships with UVA, Stony Brook University and Mississippi State University. Each position as a research assistant professor helped him develop his skills in precision measurements and experimental design. In 2023, he joined Jefferson Lab as a staff scientist in Experimental Halls A/C. Throughout his career, Gal worked closely with mentors who shaped his approach to physics and collaboration. “At this point, Cip is one of the leading mid-career experts on all things relevant to the MOLLER experiment,” said Krishna Kumar, a University of Massachusetts, Amherst professor of physics and MOLLER spokesperson. “As we pivot to data collection and physics analysis, I expect he will be one of the leaders of the team driving the analysis to accomplish the goals of the experiment.” For Gal, that leadership potential stems directly from his commitment to teamwork. “The research that I want to do and the things that I want to discover can’t be done without collaboration, not only with experimental and theoretical physicists here at the lab, but also at the universities,” Gal said.

Looking Forward The DOE Office of Science Early Career Research Program, established in 2010, supports outstanding scientists at a DOE national laboratory or Office of Science user facility within 12 years of having earned their doctorate degree across disciplines including nuclear physics. The program aims to support the vision, creativity and effort of early career faculty to drive innovation in the basic science enterprise. For Gal, the award provides resources and time to tackle MOLLER’s technical challenges and prepare for the experiment’s data collection phase. “Cip is a fantastic collaborator,” said Kumar. “He communicates effectively regardless of the audience, and the fact that he acknowledges the need for collaboration demonstrates his maturity and potential for leadership.” Beyond the immediate research, Gal sees the award as validation of his approach: combining precision measurement techniques with innovative detector design to push the boundaries of what physics can reveal about nature’s fundamental workings. It also validates something simpler: persistence. “I think for these very competitive awards, it matters a lot to be able to stand out, to have something that is unique on its own,” Gal said. He applied in 2024, received feedback, refined his proposal, and won on his second attempt in 2025. “Ciprian thrives on difficult tasks,” said Deshpande. “He understands not only the award’s value to his own career but, more importantly, the visibility this recognition brings to the MOLLER project and Jefferson Lab. His persistence therefore does not surprise me, and I am delighted by his success.” For researchers working at the frontier of nuclear physics, success often means spending years preparing for measurements that take only hours or days to complete. The payoff comes when those measurements reveal something unexpected, a crack in our understanding that points toward deeper truths. Gal’s work on MOLLER continues that tradition, using precision as a tool to probe whether the Standard Model tells the whole story or whether the universe has more secrets waiting to be discovered. For a scientist who once believed a single book could explain everything, the possibility of discovering something entirely new might be even better than having all the answers.

Further Reading

https://moller-docdb.physics.sunysb.edu/cgi-bin/DocDBTest/public/ShowDocument?docid=998

https://journals.aps.org/prc/abstract/10.1103/PhysRevC.109.024323

https://arxiv.org/abs/2411.10267

Contact: Michelle Alvarez, Jefferson Lab Communications Office, malvarez@jlab.org

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Jefferson Science Associates, LLC, manages and operates the Thomas Jefferson National Accelerator Facility, or Jefferson Lab, for the U.S. Department of Energy’s Office of Science. JSA is a wholly owned subsidiary of the Southeastern Universities Research Association, Inc. (SURA).

DOE’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

Newswise — NEWPORT NEWS, VA – The U.S. Department of Energy (DOE) Advanced Research Projects Agency-Energy (ARPA-E) has selected DOE’s Thomas Jefferson National Accelerator Facility to lead two research projects that will develop new technologies for better managing the waste from nuclear power plants. The $8.17 million total in grants come from the Nuclear Energy Waste Transmutation Optimized Now (NEWTON) program.

The goal of both projects is to improve existing particle accelerator technologies, one of Jefferson Lab’s key areas of expertise, and repurpose them for applications beyond fundamental research.

“Based on our own success in developing cutting-edge accelerator technologies to enable scientific discoveries, we believe that there is a contribution we can make with the experience we have gained over the last few decades,” said Rongli Geng, who is a principal investigator on both grants. Geng heads the SRF Science & Technology department in Jefferson Lab’s Accelerator Operations, Research and Development division.

Accelerator-Driven Systems Save the Day

According to ARPA-E, unprocessed used nuclear fuel “reaches the radiotoxicity of natural uranium ore after approximately 100,000 years of cooling. Partitioning and recycling of uranium, plutonium, and minor actinide content of used nuclear fuel can dramatically reduce this number to around 300 years.” The NEWTON program grants are aimed at enabling this recycling effort, so that it can be applied to “the entirety of the U.S. commercial used nuclear fuel stockpile within 30 years.”

This work is aimed at moving toward economic viability of transmutation of nuclear waste, a key priority of the NEWTON program. Specifically, the NEWTON grants will support the further development of accelerator-driven systems (ADS). ADS can transform highly radioactive and long-lived nuclear waste into less radioactive, shorter-lived materials, while also producing additional electricity.

An ADS is composed of a particle accelerator that propels a beam of high-energy protons at a target material such as liquid mercury. As the protons interact with the target, the material “spalls” or releases neutrons that are directed at containers of spent nuclear fuel.

“These neutrons will interact with these unwanted isotopes and convert them into more manageable isotopes that you can either try out for some beneficial use or bury underground. Instead of having a lifetime of 100,000 years in storage, for example, you can shorten the storage years down to 300,” Geng said.

Jefferson Lab’s Continuous Electron Beam Accelerator Facility (CEBAF) is a state-of-the-art particle accelerator that represented a huge leap forward in efficiency when it came online for its first experiment in 1995. It was the first large-scale installation of superconducting radiofrequency technology. Today, it supports the research for more than 1,700 nuclear physicists worldwide.

SRF technology powers many of the most advanced research accelerators in the world, including CEBAF and the accelerator that powers the Spallation Neutron Source at DOE’s Oak Ridge National Laboratory. Both accelerators are DOE Office of Science user facilities that enable research in the basic and applied sciences.

Improving ADS Technology

The first project aims to amp up the SRF particle accelerator components in ADS. The focus in this grant is on boosting the components’ efficiency.

In today’s world-class research machines, SRF particle accelerator cavities are made of a pure, silver-colored metal called niobium. Niobium becomes superconducting at extremely low temperatures, a key requirement for their efficiency. The downside to that efficiency is that big research machines must be supported by separate and costly cryogenic refrigeration facilities.

Recently, Jefferson Lab and other research facilities have found that coating the inside surfaces of pure niobium accelerator cavities with tin can make these components even more efficient, allowing them to not only operate at higher temperatures but also with standard commercial cooling units. This work builds on the research and development work supported by DOE’s Nuclear Physics (NP) program and NP’s Early Career Award (ECA) program.

The $4,217,721 grant will allow collaborators from Jefferson Lab, RadiaBeam Technology and Oak Ridge National Lab to further improve the cavities. The researchers plan to test niobium-tin cavities that have specifically been designed to accelerate protons for spalling neutrons. 

“Those are based on the mature Spallation Neutron Source cavity design, but we will add the new tin material on this existing design,” explained Geng. “So that will be tested together with our partners at Oak Ridge National Lab.”

A second goal of the grant is to design new SRF cavities that feature a more complicated design but will drive the machine efficiency even higher with enhanced neutron spallation.

“We’re going to design, build and test a new class of cavities called the spoke cavities,” Geng said. “Very likely, the whole machine will be based on this SRF technology, so this is the kind of innovation that is going to be an additive value.”

The Driving Force for ADS

The second project will focus on powering up the SRF accelerator cavities inside the ADS particle accelerators. For that, the researchers will turn to a common component that also powers the pops that turn ordinary corn kernels into light and fluffy popcorn: the magnetron.

In particle accelerators, magnetrons would provide the power that the SRF cavities harness to propel particle beams. The tricky part here is that the frequency of the energy supplied by the magnetron must match the frequency of the particle accelerator cavity, which is 805 Megahertz.

“We need a lot of power – 10 Megawatts or more. That’s why the efficiency becomes very critical,” Geng said.

For the $3,957,203 grant, the team will be working with Stellant Systems, one of the major players in magnetron manufacturing, to produce advanced magnetrons that can be combined to boost performance at the design frequency. The project team also includes General Atomics Energy Group and Oak Ridge National Laboratory.

“Stellant is tasked to design and prototype this new magnetron, and we’re going to collaborate with General Atomics and Oak Ridge National Lab to do the power combining test,” Geng explained. “That’s the main objective: demonstrate the high power, high efficiency at 805 Megahertz.”

He added that this work builds on research and development work supported by DOE’s Accelerator R&D and Production (ARDAP) program. This program helps ensure that new and emerging accelerator technology will be available for future discovery science and societal applications. Its support was instrumental in developing the technologies that are now at a place where they are ready to be adapted to contribute to the goal of safely maintaining the waste materials produced in nuclear power generation.

Both projects are also already on the path to commercialization of these technologies. By including commercial entities in these initial phases, Jefferson Lab and its partners are helping to not only transfer the specialized knowledge and expertise that will make the resulting technologies successful, but they are also developing these technologies with considerations of the capabilities of companies who would be manufacturing ADS and supporting their operations.

According to Geng, “The challenge is to really translate the accelerator science from where we are right now in terms of technology readiness to where the technology needs to be for this application.”

Further Reading:
Jefferson Lab Research and Technology Partnerships Office
Jefferson Lab Dedicates Niobium-tin Particle Accelerator Prototype
Benchmarking CEBAF
Supercool Delivery: Final Section of Souped-Up Neutron Source Trucks Out of Jefferson Lab
Jefferson Lab technology, capabilities take center stage in construction of portion of DOE’s Spallation Neutron Source accelerator
Smoother Surfaces Make for Better Accelerators
Adapting Particle Accelerators for Industrial Work
Mixing Metals for Improved Performance
Conduction-cooled Accelerating Cavity Proves Feasible for Commercial Applications
Liquid Helium-Free SRF Cavities Could Make Industrial Applications Practical
Award enables research for more efficient accelerators
Microwave Popcorn to Particle Accelerators: Magnetrons Show Promise as Radiofrequency Source

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Jefferson Science Associates, LLC, manages and operates the Thomas Jefferson National Accelerator Facility, or Jefferson Lab, for the U.S. Department of Energy’s Office of Science. JSA is a wholly owned subsidiary of the Southeastern Universities Research Association, Inc. (SURA).

DOE’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 https://energy.gov/science