RUI: Dissipative Dynamics of the Quark Gluon Plasma

Gettysburg College, Gettysburg PA

Investigators

Abstract

An understanding of why the universe is the way it is right now depends critically on our understanding of the various phase transitions that have occurred since the beginning of time until now. A key phase transition in this chain is called the quark gluon plasma (QGP) phase transition. This phase transition has the distinction of being the only one that is experimentally accessible using the current generation of particle accelerators. Experiments already performed at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab have reached the temperature necessary to trigger the emergence of a quark-gluon plasma; however, the temperatures generated were only slightly higher than the phase transition temperature of 2 trillion degrees K. Experiments recently carried out at higher collision energies at the Large Hadron Collider (LHC) and CERN have generated states with temperatures approaching four times the critical temperature for the transition to the plasma phase. A large part of the QGP-physics theoretical effort is dedicated to describing the thermalization and subsequent evolution of the matter produced using viscous hydrodynamical models. The success of these models to describe the collective flow of the matter created during heavy ion collisions at RHIC is remarkable. It seems that the data for the elliptic flow of the particles created during the event is compatible with the matter having a small shear viscosity approaching the limit of a "perfect fluid." However, key uncertainties still remain in the application of viscous hydrodynamical models that may impact upcoming experiments at the Large Hadron Collider (LHC). One of the primary uncertainties centers on the question of when is the appropriate time to begin a viscous hydrodynamical description of the matter that is created in the collision. Traditional viscous hydrodynamical treatments rely on an implicit assumption that the system is very close to thermal equilibrium and isotropy in momentum space. In practice, the evolution of the deviations from a thermal isotropic state is described by viscous hydrodynamical evolution. However, such descriptions can break down at the earliest times after the collision due to the presence of large momentum-space anisotropies. In this work I will extend and develop a new method for deriving dynamical equations for the evolution of the quark gluon plasma which relaxes one of the assumptions implicit in hydrodynamical descriptions, namely the assumption that the system is nearly isotropic in momentum space. The new method reorganizes the expansion of the one particle distribution function around an anisotropic state described by space-time dependent ellipticities and an anisotropic temperature. The resulting coupled partial differential equations can be used to describe the evolution of the system during the entire history of the quark gluon plasma. The research funded should have a significant impact on our understanding the non-equilibrium dynamics of ultrarelativistic systems. There is also an overarching educational goal to involve undergraduate physics majors in an active research program. The proposal involves the inclusion of two undergraduate research assistants who will receive training in analytic and numerical methods. This kind of training is crucial to the future success of the United States scientific programs and to attracting talented students to scientific careers.