Relativistic Heavy Ion Collider The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) collides gold nuclei at an energy of 200 GeV per nucleon pair. Collisions of gold nuclei at this energy can produce a novel state of matter similar to the matter that existed in the universe a few microseconds after the Big Bang. RHIC can also collide polarized protons at energies up to 500 GeV per nucleon pair to study the spin structure of the proton. RHIC can also collide non-identical ions such as deuterons colliding with gold nuclei.

STAR The Solenoidal Tracker at RHIC (STAR) is a detector at RHIC designed to study collisions of gold nuclei. STAR is based on a time projection chamber (TPC) that can track the thousands of particles produced in RHIC collisions. STAR also includes a room temperature solenoidal magnet, a silicon vertex tracker, an electromagnetic calorimeter, two forward TPCs, and a photon multiplicity detector. A time-of-flight system is being constructed for STAR. A central collision of two gold nuclei at 200 GeV per nucleon pair in STAR is shown to the right. The charged particles produced in the collision travel through the gas volume of the TPC, ionizing the gas as they travel. These tracks are reconstructed and drawn using a color representing the density of the ionization of moving charged particle. The magnetic field causes the tracks to travel in a helical trajectory. The magnetic field allows the extraction of the momentum of the particles as well as the sign of their electric charge. There are about 1500 tracks in this event.

Gary Westfall standing on top of the STAR detector.