Seminar in Hadronic Physics

Self-consistent Cooper-Frye particlization of a viscous fluid and its applications to LHC heavy-ion physics

Zachary Wolff

Purdue University

With over 150 inverse microbarns of Pb-Pb data taken at the LHC and more to come at 5 TeV later this year, quantitative calculations of Quark-Gluon Plasma (QGP) properties such as the shear viscosity to entropy density ratio are well underway. Many theoretical models use viscous hydrodynamics in the early stages of QGP evolution and compare results to experiment by converting this fluid to particle distributions once the fluid has expanded and cooled. This conversion, typically done in the Cooper-Frye formalism, is ambiguous for viscous fluids. I compute these particle distributions in a self-consistent way by solving the linearized Boltzmann equation and contrast the solutions to those obtained using the ad-hoc “democratic Grad” ansatz typically employed in which distributions are independent of particle dynamics. I show how the conversion method affects identified particle observables such as elliptic and higher harmonic flow at LHC energies and discuss the ramifications for extracted values of QGP properties.