HIC for FAIR Kernphysikalisches Kolloquium

Location: Physics Building, PHYS 2.116
Time: Thursday, May 15, 4:30-5:30pm (s.t.) (plus 10min for discussion)
Contact: hees@fias.uni-frankfurt.de

Using next-to-leading order perturbative QCD and a conjecture of saturation to suppress the low-energy gluon production, we calculate the initial energy densities and formation times for the dissipative fluid dynamical evolution of the quark-gluon plasma produced in ultrarelativistic heavy ion collisions [1,2]. Identifying the model uncertainties of this NLO-updated "EKRT" model, we demonstrate the predictive power of the approach by obtaining a good global agreement with the measured centrality dependence of the charged particle multiplicities, $p_T$ spectra and elliptic flow simultaneously for the Pb+Pb collisions at the LHC and Au+Au at RHIC. In particular, the shear viscosity-to-entropy ratio in the different phases of QCD matter is simultaneously constrained by all these data. To study higher cumulants $v_n$ and their event-by-event (EbyE) distributions, we are currently engaged in modeling the EbyE fluctuations of saturated minijet production in this framework. Also these results will be reported. In the beginning of the talk, I will look back at the key predictions of the original EKRT model, including the centrality dependence of the charged multiplicity vs. number of participants.

[1] R. Paatelainen, K. J. Eskola, H. Holopainen and K. Tuominen, Phys. Rev. C 87 (2012) 044904
[2] R. Paatelainen, K. J. Eskola, H. Niemi and K. Tuominen, Phys. Lett. B 731 (2014) 126

Nuclear Physics Colloquium

Determining QCD matter viscosity from fluid dynamics with saturated minijet initial conditions in ultrarelativistic A+A collisions

Kari Eskola (Department of Physics, Unitersity of Jyväskylä)