Milestone caps a quarter century of groundbreaking discoveries — with more to come from final run’s largest-ever dataset — plus technological advances in accelerators, detectors, and computing
UPTON, N.Y., Feb. 6, 2026 — Just after 9 a.m. on Friday, Feb. 6, 2026, final beams of oxygen ions — oxygen atoms stripped of their electrons — circulated through the twin 2.4-mile-circumference rings of the Relativistic Heavy Ion Collider (RHIC) and crashed into one another at nearly the speed of light inside the collider’s two house-sized particle detectors, STAR and sPHENIX. RHIC, a nuclear physics research facility at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, has been smashing atoms since the summer of 2000. The final collisions cap a quarter century of remarkable experiments using 10 different atomic species colliding over a wide range of energies in different configurations. The RHIC program has produced groundbreaking discoveries about the building blocks of matter and the nature of proton spin and technological advances in accelerators, detectors, and computing that have far surpassed scientists’ expectations when this discovery machine first turned on.
“RHIC has been one of the most successful user facilities operated by the DOE Office of Science, serving thousands of scientists from across the nation and around the globe,” said DOE Under Secretary for Science Darío Gil. “Supporting these one-of-a-kind research facilities pushes the limits of technology and expands our understanding of our world through transformational science — central pillars of DOE’s mission to ensure America’s security and prosperity.”
Gil was in the Main Control Room of Brookhaven Lab’s collider complex to officially end the 25th and final run at RHIC in advance of announcing the next major milestone in the construction of the Electron-Ion Collider (EIC), a state-of-the-art nuclear physics research facility that will be built by reusing major components of RHIC.
“It’s been an amazing run,” said Wolfram Fischer, chair of Brookhaven Lab’s Collider-Accelerator Department (C-AD), speaking of the entirety of the RHIC program. As head of C-AD, Fischer is responsible for the day-to-day, year-to-year operations of the collider and all its ancillary accelerator infrastructure. “Experiencing the challenges of first trying to get beams to circulate during commissioning in the fall of 1999, one could not have dreamed how far the performance of this machine would come,” he said. “We’ve pushed well beyond the original design in terms of the number of collisions we can produce, the energy range of those collisions, the variety of ions we’ve collided, and our ability to align the spins of protons and maintain a high degree of this alignment or polarization.”
The 25th and final run produced the largest-ever dataset from RHIC’s most energetic head-on smashups between two beams of gold ions, among the heaviest ions collided at RHIC. It also yielded a treasure trove of proton-proton collisions that will provide essential comparison data and insight into proton spin, a set of low-energy fixed target collisions to complete RHIC’s “beam energy scan,” and a final burst of oxygen-oxygen interactions. All this data will add to that collected previously by RHIC’s detectors — STAR, which has been running with many upgrades since RHIC’s beginning; PHENIX, another original RHIC detector that ceased operations in 2016; PHOBOS and BRAHMS, two smaller original detectors that ran from 2000 through 2005 and 2006, respectively; and sPHENIX, RHIC’s newest most rapid-fire collision “camera,” which came online in 2023.
This final run generated the primary data set for the new sPHENIX experiment. This year, sPHENIX accumulated more than 200 petabytes of raw data — or 200 quadrillion bytes — more than all previous RHIC raw datasets combined. This massive dataset includes 40 billion snapshots of the unique form of matter generated in gold-ion collisions.
Collectively, the RHIC measurements will fill in missing details in physicists’ understanding of how a soup of fundamental particles known as quarks and gluons — which last existed in nature some 14 billion years ago, a microsecond after the Big Bang — coalesced and converged to form the more ordinary atomic particles that make up everything visible in our world today. Recreating this primordial matter, known as a quark-gluon plasma (QGP), was the primary reason for building RHIC. RHIC’s energetic collisions of heavy ions such as gold were designed to set quarks and gluons free from “confinement” within protons and neutrons by melting the boundaries of these nuclear particles.
Thanks to considerable contributions from Japan’s RIKEN institute, RHIC was also built with unique capabilities for polarizing protons so that physicists could explore the origins of proton spin. This intrinsic quantum property, somewhat analogous to a planet spinning on its axis, has been leveraged to develop powerful technologies like nuclear magnetic resonance imaging and medical MRIs. RHIC’s polarized proton collisions have opened a new window into the mystery of how spin arises from the proton’s quarks and gluons.
PHENIX and STAR have both collected and published results from large swaths of spin-polarized collisions using selection “triggers” to decide which events to capture and study. During Run 25, sPHENIX became the world’s first detector to record a continuous streaming dataset from RHIC’s spin-polarized proton collisions — thus eliminating the need for triggers and potentially paving the way for unanticipated discoveries.
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