Nuclear physics researchers at 鶹Ƶ and all over the world have been searching for violations of the fundamental symmetries in the universe for decades.
Much like the “Big Bang” (approximately 13.8 billion years ago), but on a tiny scale, they briefly recreate the particle interactions that likely existed microseconds into the formation of our universe which also likely now exist in the cores of neutron stars. To better understand these properties, the STAR Collaboration researchers develop precision particle detectors for experiments (collisions of gold nuclei) and analyze measurements at the powerful atom-smashing Relativistic Heavy Ion Collider (RHIC), a U.S. Department of Energy (DOE) Office of Science user facility at DOE’s Brookhaven National Laboratory in Upton, New York.
Large collaborations from around the world are needed to carry out these experiments. Each institution has its own distinct physics priorities. The 鶹Ƶ group, led by Declan Keane, Ph.D., professor in the Department of Physics, searches for new antimatter nuclei and uses measurements of anisotropy (the extent to which the created matter does not emerge symmetrically in all directions) to learn about fluid-like behavior and phase transitions in the dense and highly excited matter created.
Recently, they were looking for evidence of “CPT” violation—a simultaneous violation of three fundamental symmetries in nature pertaining to the reversal of charge, parity (mirror symmetry), and time. If a nucleus and its antimatter partner did not have exactly the same mass and binding energy, this would violate CPT symmetry and physicists would need to reconsider their theories of the universe.
With their peers from over 65 research institutions, seven current 鶹Ƶ researchers as well as several alumni from the Department of Physics, in the College of Arts and Sciences, published results in the journal Nature Physics, which test matter-antimatter symmetry for the first time in a context where the binding of a new type of quark in an anti-nucleus is investigated. The research was carried out in close collaboration with a former 鶹Ƶ postdoctoral researcher, now a Fudan University professor, Jinhui Chen, Ph.D., and his Ph.D. student Peng Liu. Spoiler alert: no violations of CPT symmetry were found.
The researchers also used the same measurements to study properties of an exotic type of nucleus in which a so-called “strange” quark is present. Ordinary nuclei contain only “up” and “down” quarks. These new measurements have important astrophysical implications for understanding the properties of ultra-dense neutron stars, where strange quarks are predicted to be present in the core.
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The 鶹Ƶ researchers on this collaborative project included Keane and fellow faculty members Spiros Margetis, Ph.D. and Veronica Antocheviz Dexheimer Strickland, Ph.D.; research scientists Irakli Chakaberia, Ph.D. and Ayman Hamad, Ph.D.; and graduate students Fareha Atatella and Yue Liang.
“Irakli had an especially prominent role in this project,” Keane said. “He was the lead person in charge of the pattern-recognition software which takes the raw electronic signals from the detector and extracts the curved trajectories of the charged particles which in turn allows us to reconstruct all the information about the particles emerging from the nuclear collisions. He is also responsible for visualization of that information.”
鶹Ƶ has several Ph.D. graduates currently working at Brookhaven’s RHIC, including Richard Witt, Aihong Tang, Gang Wang, Mike Lomnitz, Amilkar Quintero, Prashanth Shanmuganathan, and Yang Wu. Former 鶹Ƶ postdoctoral researchers working there include Christina Markert, Jinhui Chen, Lokesh Kumar, and Subhash Singha.
To learn more about earlier accomplishments of the researchers in Keane’s research group, visit his faculty profile page at: /physics/profile/declan-keane.
“Planning for the STAR experiment started off with about a half-dozen institutions, including 鶹Ƶ, around 1990,” Keane said. "Today, there are 67 institutions worldwide in the STAR collaboration.”
To learn more about 鶹Ƶ’s Department of Physics, visit: /physics
About Brookhaven National Laboratory
Brookhaven National Laboratory is supported by the U.S. Department of Energy’s Office of Science. 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
Image caption: Inner vertex components of the STAR detector at the Relativistic Heavy Ion Collider (right hand view) allow scientists to trace tracks from triplets of decay particles picked up in the detector's outer regions (left) to their origin in a rare "antihypertriton" particle that decays just outside the collision zone. BROOKHAVEN NATIONAL LABORATORY
Photo caption:
The Heavy Flavor Tracker at the center of the STAR detector. BROOKHAVEN NATIONAL LABORATORY/FLICKR
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