RHIP Group at UT Austin

Relativistic Heavy Ion Physics

The Relativistic Heavy-Ion Physics Group

The study of collisions between atomic nuclei at very high energies is an international scientific enterprise the main goal of which is to produce, for a very brief time an ultra-dense, ultra-hot system of quarks and gluons in the laboratory and to then perform measurements of this exotic system of particles. The nucleus of an atom is composed of roughly equal numbers of protons and neutrons which are held together by the nuclear force. Protons and neutrons are in turn made out of point-like particles called quarks and gluons. We have a fairly good understanding of how quarks and gluons interact to form protons and neutrons, and the nominal structure of atomic nuclei in terms of protons and neutrons has been accurately understood for many years. But what we do not yet understand is how a system of quarks and gluons in a large volume behave, such as existed in the very early Universe a few micro-seconds after the Big Bang. By colliding large, or "heavy" atomic nuclei such as gold (Au with 197 protons and neutrons) or lead (Pb with 208 protons and neutrons) at large collider accelerator facilities we hope to create a "large" system of quarks and gluons which are briefly deconfined from their normal confined state within protons and neutrons. By measuring and analyzing the distributions and types of particles blown out of these violent collisions we can infer new information about how the elementary quarks and gluons interacted while in this brief (one billionth of a trillionth of a second), dense (a million billion times the density of water) and hot (several trillion degrees) phase of strongly interacting matter.

Our group conducts experiments and analyzes the data from two large facilities: the STAR (Solenoidal Tracker at RHIC) experiment at the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory in Long Island, NY and the ALICE (A Large Ion Collider Experiment) experiment at the Large Hadron Facility (LHC) at CERN outside Geneva, Switzerland.