sPHENIX Detector Reports First Physics Measurements at RHIC

Brookhaven’s sPHENIX detector at the Relativistic Heavy Ion Collider (RHIC) has reported its first physics measurements of gold-ion collisions. The detector recorded precision counts of thousands of charged particles and their energies from head-on gold-gold impacts.

These early results confirm the detector’s performance. They pave the way for its main mission: exploring the quark-gluon plasma (QGP). This plasma is the hot, dense state of matter thought to have filled the universe microseconds after the Big Bang.

The quark-gluon plasma is an exotic state of matter. It is made of free quarks and gluons. This plasma existed microseconds after the Big Bang. Colliding heavy nuclei at RHIC creates a tiny fireball where nuclear matter “melts” into this plasma.

sPHENIX found that head-on collisions produce about ten times more charged particles and energy than glancing collisions. This matches earlier RHIC results and confirms the detector is performing as designed.

With this baseline established, researchers will pursue the QGP’s rarest probes. These include fully reconstructed jets. They will study how quarks and gluons lose energy in the plasma.

RHIC’s final 2025 run of gold-ion collisions will exploit every detector’s capabilities. CERN’s LHC collides lead nuclei at much higher energy, and its experiments have observed similar QGP effects.

sPHENIX’s precise RHIC measurements will enrich the global picture of the plasma. Next, sPHENIX will treat energetic jets as a microscope on the QGP, comparing energy loss in heavy-quark vs. light-quark jets.

The first measurements establish the basis for sPHENIX’s QGP program. They herald the start of a very exciting chapter of discovery.