Three Brookhaven Lab Physicists named Fellows of American Physical Society

UPTON, NY—Three physicists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have been named Fellows of the American Physical Society (APS). With nearly 50,000 members from academia, government, and industry, APS seeks to advance and share physics knowledge through research journals, scientific meetings, and activities in education, outreach, and advocacy. Each year, no more than one half of one percent of current APS members are elevated to the status of fellow through a nomination and selection process. Fellows are recognized for their exceptional contributions to physics, including in research, applications, leadership and service, and education.

Bjoern Schenke, a physicist in the nuclear theory group at Brookhaven Lab and an adjunct professor at Stony Brook University, is being recognized for his quantitative descriptions of the evolution of matter created in heavy-ion collisions at the Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC).

Citation: “For outstanding contributions to the quantitative description of the spacetime evolution of the QCD matter formed in heavy-ion collisions.”

“I am greatly honored to be named a fellow of the APS. I am deeply indebted to all my outstanding collaborators and thank Brookhaven Lab and the Nuclear Theory Group for the stimulating work environment and continued support,” Schenke said. “The future of high energy nuclear physics is extremely exciting, and it is truly a privilege to play a role in our combined experimental and theoretical efforts to better understand the visible matter we are made of.”

Schenke’s work centers on developing quantitative descriptions of the types of matter created in particle collisions at the Relativistic Heavy Ion Collider (RHIC), a DOE Office of Science user facility located at Brookhaven Lab, and the Large Hadron Collider (LHC) at Europe’s CERN laboratory. By colliding various types of particles, including the nuclei of atoms such as gold and lead, respectively, these powerful “atom smashers” can recreate conditions that existed in the very early universe, before protons and neutrons existed. Scientists study the collisions to explore the most fundamental building blocks of visible matter—the quarks and gluons that make up the protons and neutrons of atoms in today’s world—and how they interact as governed by the theory known as quantum chromodynamics (QCD).

A pioneering model of heavy-ion collisions known as MUSIC, developed by Schenke and his collaborators, led to innovative ideas and techniques to calculate relativistic viscous hydrodynamics—how a fluid would flow in a system where particles move at close to the speed of light. Schenke’s work shows that this hydrodynamic behavior provides a robust quantitative description of bulk data at RHIC and the LHC. This approach enabled the quantitative extraction of key characteristics of the quark-gluon plasma (QGP), which is created when these energetic collisions melt the boundaries of individual protons and neutrons. That work helped to affirm the description of QGP as a nearly perfect fluid.  

Schenke and colleagues also developed a model, known as the IP-Glasma model, to describe the behavior of the strong color-charged electromagnetic fields of QCD that are generated by gluon matter released in the earliest stages of a heavy-ion collision. Matching the spacetime evolution of this matter to hydrodynamics significantly improved quantitative understanding of the initial conditions created in heavy-ion collisions. By combining this understanding with the MUSIC model, Schenke’s work spurred significant advances in quantifying how quark-gluon matter thermalizes to become a plasma in a fleeting state of thermodynamic equilibrium.

Theory work by Schenke has also provided insight into earlier experiments probing the internal structure of protons, including Germany’s HERA experiment, advancing understanding of how those results relate to results from collisions of protons with nuclei at RHIC and the LHC. His work with other theorists is helping to map out the “QCD phase diagram,” which shows how quarks and gluons evolve to become protons and neutrons under various conditions of temperature and particle density in heavy-ion collisions over a wide range of energies.

In addition, his theory contributions lay important groundwork for upcoming future experiments, including studies of jets using RHIC’s brand new sPHENIX detector, and searches for signs of dense states of gluons at the upcoming Electron-Ion Collider (EIC).

Bjoern Schenke earned his Ph.D. in physics based on research on quark-gluon plasma from Goethe University in his native Germany in 2008. After conducting postdoctoral research as part of a fellowship at McGill University, he joined Brookhaven Lab as a Research Associate in 2010, became a Goldhaber Distinguished Fellow in 2012, an associate physicist in 2014, and a full research staff physicist in 2017. He received a Young Scientist Award from the International Union of Pure and Applied Physics in 2013, was selected by the DOE for an Early Career Research Program Award in 2014, and was awarded the Zimányi Medal in Nuclear Theory in 2017.

Alexei Fedotov, a physicist in Brookhaven Lab’s Collider-Accelerator Department, is being recognized for his contributions to a beam-cooling technique that increases collision rates at the Relativistic Heavy Ion Collider (RHIC).

Citation: “For the demonstration of hadron beam cooling with RF accelerated electron beams.”

“I am extremely honored to be elected an APS Fellow by my colleagues and peers,” Fedotov said. “This honor is made possible by the privilege I have of working with outstanding collaborators here at Brookhaven Lab. It is very gratifying to see that our achievements are recognized by the physics community.”

Fedotov led the team that successfully demonstrated the world’s first use of radiofrequency (RF)-accelerated electron bunches to extract heat from ion beams at a collider. The project, dubbed “Low Energy RHIC electron Cooling” (LEReC) was shown to maximize ion collision rates at energies below the nominal injection energy at RHIC. These low-energy collisions were essential for collecting data on the various phases of nuclear matter as part of RHIC’s effort to map out nuclear phases over a wide range of conditions.

The method also paves the path for higher-energy cooling at a future Electron-Ion Collider (EIC). All previous electron coolers used direct-current (DC)-accelerated electron beams, which are accelerated through a constant voltage. This limits the energy of these electron beams to a few million electron volts and would be insufficient for high-energy cooling applications in the energy range of the EIC, which is measured in billions of electron volts. The successful use of radiofrequency cavities to accelerate electron beams and RF correctors to reduce momentum spread in the electron bunches while maintaining the high currents needed to extract heat from ion beams shows great promise for use at the future EIC.

Fedotov was involved in every aspect of design, construction, and commissioning of a range of systems to make the cooling work. LEReC is based on state-of-the-art accelerator physics and technology including: high-quantum-efficiency photocathodes with a sophisticated delivery system which can hold up to 12 cathodes simultaneously; a high-power laser beam with laser shaping and stabilization; a high-voltage high-current DC gun; RF gymnastics using several RF cavities; and additional instrumentation and controls. Unlike in any previous coolers, the LEReC cathode is not immersed in a magnetic field and no continuous magnetic field with precise solenoids is required in the cooling regions. This significantly simplifies the technical design.

Prior to installation, Fedotov carried out simulations to demonstrate that the envisioned scheme would work. He also conceived a strategy for cooling beams in both RHIC rings with a single beam of electrons. Under his leadership, the team completed commissioning the new cooling scheme—a task that typically takes a few years—within half a year while RHIC’s physics program was running.

Following the successful commissioning in 2019, the system was used to cool ion beams in both collider rings with ion beams in collision, making it the world’s first application of electron cooling techniques directly in a collider. LEReC successfully operated for the RHIC physics program in 2020 and 2021 and was essential in achieving the required luminosity (collision rate) goals.

Alexei Fedotov received his Ph.D. in accelerator physics from the University of Maryland at College Park in 1997. He joined Brookhaven National Laboratory in 1999 as assistant physicist and was granted tenure in 2008. In 2019, he received Brookhaven Lab’s Science and Technology Award, the Laboratory’s highest honor. In 2021, he was awarded Dieter Möhl Medal, a worldwide recognition for outstanding contributions to the development and application of particle beam cooling.

Elizabeth (Libby) Ricard-McCutchan, a physicist in the National Nuclear Data Center (NNDC) at Brookhaven Lab, is being recognized for a wide range of contributions to the field of nuclear science including explorations of nuclear structure, fundamental physics, and developing new tools for managing and finding deeper meaning in nuclear data.

Citation: “For innovative and distinguished contributions to understanding the evolution of collectivity in heavy nuclei, critical precision experiments to test ab initio methods in light nuclei, seminal analyses of antineutrino spectra, and the development of new database tools to understand nuclear data.”

“I feel truly humbled and honored to be named an APS fellow,” Ricard-McCutchan said.  “I have been fortunate enough to learn from and work with outstanding scientists at Yale University, Argonne National Laboratory, and the NNDC whose support through my career has made possible this recognition.”

Ricard-McCutchan’s early work as a graduate student and then postdoctoral fellow at Yale focused on understanding nuclear structure using a macroscopic, symmetry-based approach. She studied the properties of deformed rare-earth nuclei using the ESTU accelerator at Yale to conduct a series of experimental studies of their gamma-ray decay and level lifetimes. Her experimental work yielded significant insights into the structure of these nuclei and the evolution of collectivity in heavy nuclei.

As part of her research, Ricard-McCutchan also developed innovative theoretical approaches that advanced the modeling of collective nuclei. A technique she developed, called Orthogonal Crossing Contours (OCC), allows scientists to optimize calculations and assess theoretical uncertainties and is now widely used in the field. It changed what had been a “hit-and-miss” modeling exercise into a systematic strategy for understanding nuclear phenomena. Such dual contributions in both experiment and theory are rare in nuclear physics.

Ricard-McCutchan then moved to a named Fellowship at Argonne National Laboratory (ANL) and conducted research at the Argonne Tandem Linac Accelerator System (ATLAS). She branched out into a new area, studying the structure and reactions of very light atomic nuclei. Through that work, she established precise new ways to test microscopic ab initio predictions of nuclei—that is, how the building blocks of nuclei contribute to nuclear structure from the bottom up. Her nuclear structure studies therefore provide complementary insight into both the large-scale collective behavior of complex many-bodied nuclei as well as how nuclear properties arise from the fundamental nuclear building blocks (protons, neutrons, quarks, and gluons) and their interactions.

From ANL, Ricard-McCutchan moved to Brookhaven National Laboratory where she joined the National Nuclear Data Center (NNDC). NNDC collects, evaluates, archives, and disseminates nuclear physics data on all nuclei for basic nuclear research and for applied nuclear technologies. While contributing to this mission, Ricard-McCutchan has continued her academic research, branching out into medical physics, reactor physics, and aspects of the science of neutrino oscillations.  She is currently involved in precise gamma-ray spectroscopy measurements of isotopes with applications in nuclear medicine and forensics. 

Ricard-McCutchan has led several new database initiatives funded by the Department of Energy. The nuclear structure data base, ENSDF, originally developed in the 1970s, is being ported to a new format which allows greater accessibility and the opportunity to store a much wider variety of information. She has developed an initiative to review manuscripts submitted for publication in various scientific journals to identify inconsistencies with the data prior to publication, thus eliminating many trivial errors.

Elizabeth Ricard-McCutchan earned her Ph.D. in physics from Yale University in 2006. She worked as a postdoc in Yale’s Wright Nuclear Structure Laboratory (2006-7), followed by two postdoctoral fellowships at Argonne National Laboratory (2007-8 and 2008-11) before joining the National Nuclear Data Center at Brookhaven National Laboratory as an Associate Scientist in 2011. She was promoted to Physicist in 2016. She serves as editor of the Nuclear Data Sheets journal, has published more than 180 research papers, given more than 60 invited talks at conferences and seminars, and has mentored 39 undergraduate students through DOE’s Science Undergraduate Laboratory Internship (SULI) program and Brookhaven’s Supplemental Undergraduate Research Program (SURP).

Schenke’s theory work, Fedotov’s accelerator design work, and Ricard-McCutchan’s studies are all supported by the DOE Office of Science (NP). RHIC at Brookhaven and the ATLAS facility at Argonne National Laboratory are both DOE Office of Science user facilities.

Brookhaven National Laboratory is supported by the Office of Science of the U.S. Department of Energy. The 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 science.energy.gov.

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