Nuclear Physics Seminar

Exploring the dynamics of strongly interacting media with dilepton tomography

Gojko Vujanovic (The Ohio State University)

Time: Monday, November 30th, 2015, 01:30 pm

Although rarely produced, electromagnetic (EM) probes provide direct insight into the new phase of matter produced in relativistic heavy-ion collisions: the Quark-Gluon Plasma (QGP). Lepton pairs (dileptons) radiated from the thermalized strongly-interacting medium are a class of EM probes that can isolate the thermal radiation from the early QGP phase of the medium. Indeed, QGP preferentially emits dileptons at high center of mass energy of the pairs (or high invariant masses), while low invariant mass dileptons originate from the late hadronic phase of medium. Having a direct access to the QGP allows to investigate its dynamical properties using a 3+1D hydrodynamical simulation. Recently, much attention has been dedicated to the study of the shear viscosity and its effects on the evolution of the medium created in heavy-ion collisions, through analyses of the hadronic final states. We show that thermal dileptons produced at the top beam energy of the Relativistic Heavy Ion Collider (RHIC) give access to the temperature dependence of shear viscosity in the QGP phase, while also allowing to study the effects of varying the relaxation time and initial conditions of the shear stress tensor. Furthermore, RHIC has published dilepton data from its Beam Energy Scan (BES) program, probing nuclear media at increasing net baryon densities. Through dilepton radiation, we also examine the importance of baryon currents on the entire evolution of the medium at various beam energies.

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