The nuclear physics research group at Rice University studies the physics properties of heavy-ion collisions at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory. In the 15 years that the STAR detector has been operating at RHIC, we have learned that  heavy-ion collisions at RHIC produce a 4-trillion degree new state of matter called the Quark Gluon  Plasma (QGP). In this state of matter, like the state of the universe a few millionths of a second after the Big Bang, the fundamental building blocks of nuclear matter behave as free particles.  Investigating the details of these collisions in a laboratory setting is a direct study of the properties of the strong nuclear force that governs the behavior of quarks and gluons.  This strong force is described by the theory of Quantum Chromo-Dynamics (QCD). Discoveries in this field of research are also important to cosmology, the study of the early universe, and to condensed-matter physics.

From 4 trillion Kelvin to 7.2 trillion ... Fahrenheit
We are currently studying in detail the transition between a QGP and ordinary matter, in which quarks and gluons are bound into protons and neutrons that make up the nucleus of the atom. We study fundamental symmetry properties of matter which appear broken in normal nuclear matter but which are expected to be restored in a QGP. We use electrons and muons, that are immune to the QGP as they pass through it, to furthermore probe early temperatures of the collisions. Measuring the yields of pairs of electrons, muons and their associated antiparticles will provide information on particle formation rates early in the collisions and also provide information on the lifetime of these hot and dense systems.

Our research focuses on measuring specific types of quarks flavors. There are six types, “flavors”, of quarks. The two lightest quarks make up ordinary matter. The heavy quark flavors are only found at high temperatures such as those produced in heavy-ion collisions. We identify particles containing these heavy flavors in order to probe the initial conditions in the collisions. Measuring these particles provides information about energy loss traversing a QGP and further refines our understanding of QCD and the behavior of nuclear matter under extreme conditions.

151016_ geurts_fitlow_003
left to right (back): David Tlusty, Joey Butterworth, Mohammed Shobaki, Jay Roberts;
(front): Daniel Brandenburg, Frank Geurts, Kefeng Xin, Geary Eppley