Introduction to RHIC’s Final Run

After 25 years of colliding gold nuclei at incredible speeds, the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory is ceasing operations. The collider’s final run, which commenced this week on Long Island, marks the beginning of the end for this venerable particle accelerator. Over the course of 2025, physicists will collect data on quark-gluon plasma, a state of matter that existed in the early universe.

The Legacy of RHIC

"The original idea behind RHIC was to create a state of matter that existed in the universe a few microseconds after the Big Bang: the quark-gluon plasma," said James Dunlop, Associate Department Chair for Nuclear Physics at Brookhaven Lab. "We succeeded in creating it, and what’s more interesting is that its properties were quite different from what we expected." Dunlop added, "The quark-gluon plasma behaves as the most perfect liquid we know of, which was an unexpected discovery."

Final Run Objectives

The top priority for RHIC’s final run is to conduct gold-on-gold collisions at energies of 200 billion electron volts. The collider will operate until June, then take a break in July and August to avoid the summer heat. According to Lijuan Ruan, co-spokesperson for the STAR detector, the run aims to collect observations on 10 billion events. "We plan to leverage our detector’s triggers to acquire a substantial number of events enriched with high-energy particles," Ruan added.

Experimental Setup

Like the Large Hadron Collider at CERN, RHIC has multiple experiments that draw data from its collisions. The sPHENIX detector will attempt to capture data from about 50 billion collision events to study the quark-gluon plasma. "By combining these RHIC measurements with high-energy experiments at the Large Hadron Collider, we’ll refine our understanding of how this exotic matter behaves as its temperature changes," said Megan Connors, a physicist at Georgia State University and co-spokesperson of sPHENIX.

Transition to the Electron-Ion Collider

When RHIC’s final run is complete, Brookhaven will transform the collider into the Electron-Ion Collider (EIC) by reusing components and adding new ones for electron acceleration. The EIC will study the strong nuclear force, which binds quarks together. "From RHIC to EIC, scientists are mapping the transition of nuclear matter from a hot, dense state to a cold state, using electrons to probe nuclear matter," said sPHENIX co-spokesperson Jin Huang.

Implications and Future Research

This basic research has implications for nuclear physics projects and understanding the primordial soup of particles that existed at the beginning of the universe. Such fundamental research is crucial for advancing our knowledge, provided that science labs receive the necessary resources to support it.

/image: An artist’s rendering of the RHIC (left) and the next-generation EIC (right). Illustration: Valerie A. Lentz/Brookhaven National Laboratory/