Aerial view of the Relativistic Heavy Ion Collider (RHIC)

Brookhaven’s Relativistic Heavy Ion Collider Begins Run 24

April 15, 2024: Today marks the startup of the 24th run of the Relativistic Heavy Ion Collider (RHIC), a U.S. Department of Energy (DOE) Office of Science user facility for nuclear physics research at DOE’s Brookhaven National Laboratory. Physicists at RHIC’s two house-sized particle detectors, sPHENIX and STAR, are eagerly awaiting the first collisions in Run 24 of protons speeding in opposite directions around the accelerator’s twin 2.4-mile-circumference rings.

At RHIC, the protons — positively charged building blocks of atomic nuclei — are polarized, meaning their “spins” are preferentially aligned. By analyzing how certain particles emerge from collisions relative to this spin direction, scientists can explore how a proton’s own internal building blocks — quarks and gluons — contribute to its overall spin.

Aerial view of RHIC accelerator complexRe: photo above – A chain of accelerators at Brookhaven National Laboratory brings protons or atomic nuclei up to speed and injects them into the counter-circulating “gold” and “blue” rings of the Relativistic Heavy Ion Collider (RHIC). Pairs of protons or ions collide at the center of two house-sized detectors, STAR and sPHENIX. Scientists analyze particles streaming out of collisions to learn about the building blocks of matter.

The proton-proton collisions also provide important comparison data for RHIC’s collisions of larger atomic nuclei. Collisions of nuclei such as gold, consisting of many protons and neutrons, recreate the conditions of the early universe by setting “free” the quarks and gluons that make up the protons and neutrons. Scientists use RHIC to explore detailed properties of the resulting quark-gluon plasma (QGP) and the strong force — the strongest force in nature — which holds quarks together in the matter that makes up our world today.

Collecting comparison proton-proton data in Run 24 is especially important for sPHENIX, a brand-new detector that saw its first gold-gold collisions last year. Run 24 is the second-to-last planned for RHIC before much of its infrastructure is converted into the future Electron-Ion Collider (EIC). Run 25 will be focused on collecting unprecedented amounts of gold-gold collision data.


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