From The Facility for Rare Isotope Beams [FRIB]: “Halos and dark matter:: A recipe for discovery”

From The Facility for Rare Isotope Beams [FRIB].


Michigan State Bloc

Michigan State University

July 22, 2022
Matt Davenport

This Hubble Space Telescope image centers on what’s known as a low surface brightness, or LSB, galaxy (blue), surrounded by more familiar-looking galaxies (yellow). Astrophysics believe that more than 95% of the matter found in LSBs is dark matter. Credit: D. Calzetti/NASA/ESAHubble.

Scientists still don’t know what Dark Matter is. But Michigan State University scientists helped uncover new physics while looking for it.

About three years ago, Wolfgang “Wolfi” Mittig and Yassid Ayyad went looking for the universe’s missing mass, better known as Dark Matter, in the heart of an atom.

Their expedition didn’t lead them to Dark Matter, but they still found something that had never been seen before, something that defied explanation. Well, at least an explanation that everyone could agree on.

“We started out looking for Dark Matter and we didn’t find it,” he said. “Instead, we found other things that have been challenging for theory to explain.”

So the team got back to work, doing more experiments, gathering more evidence to make their discovery make sense. Mittig, Ayyad and their colleagues bolstered their case at the National Superconducting Cyclotron Laboratory, or NSCL [below], at Michigan State University.

Working at NSCL, the team found a new path to their unexpected destination, which they detailed June 28 in the journal Physical Review Letters [below]. In doing so, they also revealed interesting physics that’s afoot in the ultra-small quantum realm of subatomic particles.

In particular, the team confirmed that when an atom’s core, or nucleus, is overstuffed with neutrons, it can still find a way to a more stable configuration by spitting out a proton instead.

“It’s been something like a detective story,” said Mittig, a Hannah Distinguished Professor in Michigan State University’s Department of Physics and Astronomy and a faculty member at the Facility for Rare Isotope Beams [below].

Shot in the dark

Dark Matter is one of the most famous things in the universe that we know the least about. For decades, scientists have known that the cosmos contains more mass than we can see based on the trajectories of stars and galaxies.

For gravity to keep the celestial objects tethered to their paths, there had to be unseen mass and a lot of it — six times the amount of regular matter that we can observe, measure and characterize. Although scientists are convinced Dark Matter is out there, they have yet to find where and devise how to detect it directly.

“Finding Dark Matter is one of the major goals of physics,” said Ayyad, a nuclear physics researcher at the Galician Institute of High Energy Physics, or IGFAE, of the University of Santiago de Compostela in Spain.

Speaking in round numbers, scientists have launched about 100 experiments to try to illuminate what exactly Dark Matter is, Mittig said.

“None of them has succeeded after 20, 30, 40 years of research,” he said.

“But there was a theory, a very hypothetical idea, that you could observe Dark Matter with a very particular type of nucleus,” said Ayyad, who was previously a detector systems physicist at NSCL.

This theory centered on what it calls a dark decay. It posited that certain unstable nuclei, nuclei that naturally fall apart, could jettison Dark Matter as they crumbled.
Dark Matter Background
Fritz Zwicky discovered Dark Matter in the 1930s when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM, denied the Nobel, some 30 years later, did most of the work on Dark Matter.

Fritz Zwicky.
Coma cluster via NASA/ESA Hubble, the original example of Dark Matter discovered during observations by Fritz Zwicky and confirmed 30 years later by Vera Rubin.
In modern times, it was astronomer Fritz Zwicky, in the 1930s, who made the first observations of what we now call dark matter. His 1933 observations of the Coma Cluster of galaxies seemed to indicated it has a mass 500 times more than that previously calculated by Edwin Hubble. Furthermore, this extra mass seemed to be completely invisible. Although Zwicky’s observations were initially met with much skepticism, they were later confirmed by other groups of astronomers.

Thirty years later, astronomer Vera Rubin provided a huge piece of evidence for the existence of dark matter. She discovered that the centers of galaxies rotate at the same speed as their extremities, whereas, of course, they should rotate faster. Think of a vinyl LP on a record deck: its center rotates faster than its edge. That’s what logic dictates we should see in galaxies too. But we do not. The only way to explain this is if the whole galaxy is only the center of some much larger structure, as if it is only the label on the LP so to speak, causing the galaxy to have a consistent rotation speed from center to edge.

Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas were met with much resistance from the astronomical community, but her observations have been confirmed and are seen today as pivotal proof of the existence of dark matter.
Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science).

Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970.

Vera Rubin measuring spectra, worked on Dark Matter(Emilio Segre Visual Archives AIP SPL).
Dark Matter Research

Super Cryogenic Dark Matter Search from DOE’s SLAC National Accelerator Laboratory at Stanford University at SNOLAB (Vale Inco Mine, Sudbury, Canada).

LBNL LZ Dark Matter Experiment xenon detector at Sanford Underground Research Facility Credit: Matt Kapust.

Lamda Cold Dark Matter Accerated Expansion of The universe http the-cosmic-inflation-suggests-the-existence-of-parallel-universes. Credit: Alex Mittelmann.

DAMA at Gran Sasso uses sodium iodide housed in copper to hunt for dark matter LNGS-INFN.

Yale HAYSTAC axion dark matter experiment at Yale’s Wright Lab.

DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB (CA) deep in Sudbury’s Creighton Mine.

The LBNL LZ Dark Matter Experiment Dark Matter project at SURF, Lead, SD.

DAMA-LIBRA Dark Matter experiment at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS) located in the Abruzzo region of central Italy.

DARWIN Dark Matter experiment. A design study for a next-generation, multi-ton dark matter detector in Europe at The University of Zurich [Universität Zürich](CH).

PandaX II Dark Matter experiment at Jin-ping Underground Laboratory (CJPL) in Sichuan, China.

Inside the Axion Dark Matter eXperiment U Washington (US) Credit : Mark Stone U. of Washington. Axion Dark Matter Experiment.

So Ayyad, Mittig and their team designed an experiment that could look for a dark decay, knowing the odds were against them. But the gamble wasn’t as big as it sounds because probing exotic decays also lets researchers better understand the rules and structures of the nuclear and quantum worlds.

The researchers had a good chance of discovering something new. The question was what that would be.

Help from a halo

When people imagine a nucleus, many may think of a lumpy ball made up of protons and neutrons, Ayyad said. But nuclei can take on strange shapes, including what are known as halo nuclei.

Beryllium-11 is an example of a halo nucleus. It’s a form, or isotope, of the element beryllium that has four protons and seven neutrons in its nucleus. It keeps 10 of those 11 nuclear particles in a tight central cluster. But one neutron floats far away from that core, loosely bound to the rest of the nucleus, kind of like the moon ringing around the Earth, Ayyad said.

Beryllium-11 is also unstable. After a lifetime of about 13.8 seconds, it falls apart by what’s known as beta decay. One of its neutrons ejects an electron and becomes a proton. This transforms the nucleus into a stable form of the element boron with five protons and six neutrons, boron-11.

In the team’s experiment published in 2019, beryllium-11 decays through beta decay to an excited state of boron-11, which decays to beryllium-10 and a proton. In the new experiment, the team accesses the boron-11 state by adding a proton to beryllium-10, that is, by running the time-reversed reaction.

But according to that very hypothetical theory, if the neutron that decays is the one in the halo, beryllium-11 could go an entirely different route: It could undergo a dark decay.

In 2019, the researchers launched an experiment at Canada’s national particle accelerator facility, TRIUMF- Canada’s particle accelerator centre [Centre canadien d’accélération des particules](CA), looking for that very hypothetical decay.

And they did find a decay with unexpectedly high probability, but it wasn’t a dark decay.

It looked like the beryllium-11’s loosely bound neutron was ejecting an electron like normal beta decay, yet the beryllium wasn’t following the known decay path to boron.

The team hypothesized that the high probability of the decay could be explained if a state in boron-11 existed as a doorway to another decay, to beryllium-10 and a proton. For anyone keeping score, that meant the nucleus had once again become beryllium. Only now it had six neutrons instead of seven.

“This happens just because of the halo nucleus,” Ayyad said. “It’s a very exotic type of radioactivity. It was actually the first direct evidence of proton radioactivity from a neutron-rich nucleus.”

But science welcomes scrutiny and skepticism, and the team’s 2019 report was met with a healthy dose of both. That “doorway” state in boron-11 did not seem compatible with most theoretical models. Without a solid theory that made sense of what the team saw, different experts interpreted the team’s data differently and offered up other potential conclusions.

“We had a lot of long discussions,” Mittig said. “It was a good thing.”

As beneficial as the discussions were — and continue to be — Mittig and Ayyad knew they’d have to generate more evidence to support their results and hypothesis. They’d have to design new experiments.

The NSCL experiments

In the team’s 2019 experiment, TRIUMF generated a beam of beryllium-11 nuclei that the team directed into a detection chamber where researchers observed different possible decay routes. That included the beta decay to proton emission process that created beryllium-10.

For the new experiments, which took place in August 2021, the team’s idea was to essentially run the time-reversed reaction. That is, the researchers would start with beryllium-10 nuclei and add a proton.

Collaborators in Switzerland created a source of beryllium-10, which has a half-life of 1.4 million years, that NSCL could then use to produce radioactive beams with new reaccelerator technology. The technology evaporated and injected the beryllium into an accelerator and made it possible for researchers to make a highly sensitive measurement.

When beryllium-10 absorbed a proton of the right energy, the nucleus entered the same excited state the researchers believed they discovered three years earlier. It would even spit the proton back out, which can be detected as signature of the process.

“The results of the two experiments are very compatible,” Ayyad said.

That wasn’t the only good news. Unbeknownst to the team, an independent group of scientists at Florida State University had devised another way to probe the 2019 result. Ayyad happened to attend a virtual conference where the Florida State team presented its preliminary results, and he was encouraged by what he saw.

“I took a screenshot of the Zoom meeting and immediately sent it to Wolfi,” he said. “Then we reached out to the Florida State team and worked out a way to support each other.”

The two teams were in touch as they developed their reports, and both scientific publications now appear in the same issue of Physical Review Letters [below]. And the new results are already generating a buzz in the community.

“The work is getting a lot of attention. Wolfi will visit Spain in a few weeks to talk about this,” Ayyad said.

An open case on open quantum systems

Part of the excitement is because the team’s work could provide a new case study for what are known as open quantum systems. It’s an intimidating name, but the concept can be thought of like the old adage, “nothing exists in a vacuum.”

In an open quantum system, a discrete, or isolated, state, analogous to boron-11 (left), mixes with an adjacent continuum of states, related to beryllium-10 (middle), which results in a new “resonant” state (right). Credit: Facility for Rare Isotope Beams.

Quantum physics has provided a framework to understand the incredibly tiny components of nature: atoms, molecules and much, much more. This understanding has advanced virtually every realm of physical science, including energy, chemistry and materials science.

Much of that framework, however, was developed considering simplified scenarios. The super small system of interest would be isolated in some way from the ocean of input provided by the world around it. In studying open quantum systems, physicists are venturing away from idealized scenarios and into the complexity of reality.

Open quantum systems are literally everywhere, but finding one that’s tractable enough to learn something from is challenging, especially in matters of the nucleus. Mittig and Ayyad saw potential in their loosely bound nuclei and they knew that NSCL, and now FRIB could help develop it.

NSCL, a National Science Foundation user facility that served the scientific community for decades, hosted the work of Mittig and Ayyad, which is the first published demonstration of the stand-alone reaccelerator technology. FRIB, a U.S. Department of Energy Office of Science user facility that officially launched on May 2, 2022 is where the work can continue in the future.

“Open quantum systems are a general phenomenon, but they’re a new idea in nuclear physics,” Ayyad said. “And most of the theorists who are doing the work are at FRIB.”

But this detective story is still in its early chapters. To complete the case, researchers still need more data, more evidence to make full sense of what they’re seeing. That means Ayyad and Mittig are still doing what they do best and investigating.

“We’re going ahead and making new experiments,” said Mittig. “The theme through all of this is that it’s important to have good experiments with strong analysis.”

NSCL was a national user facility funded by the National Science Foundation, supporting the mission of the Nuclear Physics program in the NSF Physics Division.

Michigan State University (MSU) operates the Facility for Rare Isotope Beams (FRIB) as a user facility for the U.S. Department of Energy Office of Science (DOE-SC), supporting the mission of the DOE-SC Office of Nuclear Physics. Hosting what is designed to be the most powerful heavy-ion accelerator, FRIB enables scientists to make discoveries about the properties of rare isotopes in order to better understand the physics of nuclei, nuclear astrophysics, fundamental interactions and applications for society, including in medicine, homeland security and industry.

The U.S. Department of Energy 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 today’s most pressing challenges. For more information, visit

Science paper:
Physical Review Letters

Physical Review Letters

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Michigan State Campus

Michigan State University is a public research university located in East Lansing, Michigan, United States. Michigan State University was founded in 1855 and became the nation’s first land-grant institution under the Morrill Act of 1862, serving as a model for future land-grant universities.

The university was founded as the Agricultural College of the State of Michigan, one of the country’s first institutions of higher education to teach scientific agriculture. After the introduction of the Morrill Act, the college became coeducational and expanded its curriculum beyond agriculture. Today, Michigan State University is one of the largest universities in the United States (in terms of enrollment) and has approximately 634,300 living alumni worldwide.

U.S. News & World Report ranks its graduate programs the best in the U.S. in elementary teacher’s education, secondary teacher’s education, industrial and organizational psychology, rehabilitation counseling, African history (tied), supply chain logistics and nuclear physics in 2019. Michigan State University pioneered the studies of packaging, hospitality business, supply chain management, and communication sciences. Michigan State University is a member of the Association of American Universities and is classified among “R1: Doctoral Universities – Very high research activity”. The university’s campus houses the National Superconducting Cyclotron Laboratory, the W. J. Beal Botanical Garden, the Abrams Planetarium, the Wharton Center for Performing Arts, the Eli and Edythe Broad Art Museum, the Facility for Rare Isotope Beams, and the country’s largest residence hall system.


The university has a long history of academic research and innovation. In 1877, botany professor William J. Beal performed the first documented genetic crosses to produce hybrid corn, which led to increased yields. Michigan State University dairy professor G. Malcolm Trout improved the process for the homogenization of milk in the 1930s, making it more commercially viable. In the 1960s, Michigan State University scientists developed cisplatin, a leading cancer fighting drug, and followed that work with the derivative, carboplatin. Albert Fert, an Adjunct professor at Michigan State University, was awarded the 2007 Nobel Prize in Physics together with Peter Grünberg.

Today Michigan State University continues its research with facilities such as the Department of Energy -sponsored Plant Research Laboratory and a particle accelerator called the National Superconducting Cyclotron Laboratory [below]. The Department of Energy Office of Science named Michigan State University as the site for the Facility for Rare Isotope Beams (FRIB). The $730 million facility will attract top researchers from around the world to conduct experiments in basic nuclear science, astrophysics, and applications of isotopes to other fields.

Michigan State University FRIB [Facility for Rare Isotope Beams] .

In 2004, scientists at the Cyclotron produced and observed a new isotope of the element germanium, called Ge-60 In that same year, Michigan State University, in consortium with the University of North Carolina at Chapel Hill and the government of Brazil, broke ground on the 4.1-meter Southern Astrophysical Research Telescope (SOAR) in the Andes Mountains of Chile.

The consortium telescope will allow the Physics & Astronomy department to study galaxy formation and origins. Since 1999, MSU has been part of a consortium called the Michigan Life Sciences Corridor, which aims to develop biotechnology research in the State of Michigan. Finally, the College of Communication Arts and Sciences’ Quello Center researches issues of information and communication management.

The Michigan State University Spartans compete in the NCAA Division I Big Ten Conference. Michigan State Spartans football won the Rose Bowl Game in 1954, 1956, 1988 and 2014, and the university claims a total of six national football championships. Spartans men’s basketball won the NCAA National Championship in 1979 and 2000 and has attained the Final Four eight times since the 1998–1999 season. Spartans ice hockey won NCAA national titles in 1966, 1986 and 2007. The women’s cross country team was named Big Ten champions in 2019. In the fall of 2019, MSU student-athletes posted all-time highs for graduation success rates and federal graduation rates, according to NCAA statistics.