Relativistic Heavy Ion Collision Studies at the LHC and RHIC

Ohio State University, The, Columbus OH

Investigators

Abstract

This award is primarily to carry out experiments with relativistic heavy ion collisions. The principal investigators are T. J. Humanic and M. A. Lisa, of the Department of Physics at The Ohio State University. Our goals for the high-energy program are threefold. Firstly, we will study the space-time properties of the extremely dense matter created at in collisions between heavy nuclei at the highest achievable energies. It is believed that this matter is a quark-gluon plasma (QGP), characterized by colored degrees of freedom at the microscopic scale. The second activity is to study the bulk phase structure of Quantum Chromodynamics (QCD), believed to be the correct theory of the Strong interaction between partons. This will be achieved by varying the conditions of the collision to lower energies, to probe the transition(s) between confined and deconfined matter. In particular, we plan to perform a novel analysis as a function of the collision energy, measuring coordinate-space anisotropies and dynamics. Thirdly, we will take the tools developed to study bulk physics in heavy ion collisions, and apply them to hadronic(p+p) collisions at similar energies. We will look particularly for collective behaviour(flow) in hadronic collisions. If our initial reports of such flow in ultrarelativistic p+p collisions are confirmed at higher energies, this raises important issues about the nature of flow, and the nature of the initial self-interacting state, itself. In the present grant ultrarelativistic heavy ion collisions will be studied with Au-Au collisions at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL), and with Pb-Pb collisions at the Large Hadron Collider (LHC) at CERN in Geneva. RHIC started delivering Au-Au collisions in Summer 2000, and the LHC, which is the highest energy heavy ion accelerator now in operation, began delivering Pb-Pb collisions at the end of 2010. In order to look for signatures that a phase transition to Quark Matter has taken place, one must study the properties of the particles produced in the collisions, such as particle momenta and multiplicities of each type that can be detected (e.g. pions, kaons, protons, and more exotic particles). This will be done at both RHIC and the LHC using the large acceptance detectors available in the STAR and ALICE experiments, respectively, which can sample most of the interesting particles per collision. The information obtained in this way can be used to determine, for example, the physical size of the interaction region (using two-particle interferometry), the temperatures reached in the collisions (from particle momentum distributions) and exotic particle production such as strange baryons. Besides the intellectual merit described above, there are broader impacts to society of this proposal in the areas of education, technology and computing. Since undergraduate students, graduate students and postdoctoral researchers will play key roles in this project, training will be provided to these groups in how to carry out research in large collaborations and in general problem solving skills. Since this research requires large-scale computing in order to acquire and analyze data on the teraflop and terabyte scale, new methods in information science, such as computing grid systems, will be developed, which can enhance the computing power of society as a whole.