Time: 10:00am,Sept. 7, Thursday, 2017

Location: Room 9409

Speaker: Dr. ZHOU You（周铀）, Niels Bohr Institute, University of Copenhagen

Title:Novel constraints on the properties of the Quark-GluonPlasma

Abstract: The primary goal of the ultra-relativistic heavy-ion collision program at the LargeHadron Collider (LHC) is to study the properties of the Quark-Gluon Plasma (QGP),a state of strongly interacting matter that is proposed to exist at hightemperatures and energy densities. Studies of azimuthal correlations of producedparticles have contributed significantly to the characterization of the mattercreated in heavy-ion collisions. Anisotropic flow, which quantifies the anisotropy ofthe momentum distribution of final state particles, is sensitive to the event-byeventfluctuating initial geometry of the overlap region, together with the transportproperties and the equation of state of the system. The successful description ofthe measured anisotropic flow coefficients by hydrodynamic calculations suggeststhat the created medium behaves as a nearly perfect fluid with a shear viscosity toentropy density ratio close to a conjectured lower bound $1/4\pi$.

In this talk, I will present flow measurements in Pb--Pb collisions at $\sqrt{s_{\rmNN}} =$ 2.76 and 5.02 TeV at the LHC. The standard anisotropic flow coefficients,as well as the recently developed anisotropic flow observables, symmetriccumulants and non-linear modes of higher order anisotropic flow, will beiscussed in detail. These measurements, together with the comparisons tohydrodynamic calculations, help constrain the initial conditions and temperature dependence of the shear and bulk viscosities of the QGP, which were not very wellconstrained by previous measurements. These comparisons could also offer newinsights into the geometry of the fluctuating initial state and further understandingof the dynamical evolution of the strongly interacting medium produced inrelativistic heavy-ion collisions at the LHC.