Elliptic flow in s = 200 GeV Au+Au collisions and s = 2.76 TeV Pb+Pb collisions: Insights from viscous hydrodynamics+hadron cascade hybrid model

摘要

Using the newly developed hybrid model VISHNU, which connects viscous hydrodynamics with a hadronncascade model, we study the differential and integrated elliptic flow v2 at different centrality bins for 200 AnGeV Au+Au collisions and 2.76 A TeV Pb+Pb collisions. We find that the average quark-gluon plasman(QGP)-specific shear viscosity η/s slightly increases from Relativistic Heavy Ion Collider to Large HadronnCollider (LHC) energies. However, a further study assuming different temperature dependencies for (η/s)QGPnshows that one cannot uniquely constrain the form of (η/s)QGP(T ) by fitting the spectra and v2 alone. Based onnour current understanding, the question whether the QGP fluid is more viscous or more perfect in the temperaturenregime reached by LHC energies is still open.