Speaker
Rajeev Bhalerao
(TIFR)
Description
Complete evolution of the strongly interacting matter formed in ultra-relativistic heavy-ion collisions is studied within a coupled Boltzmann and relativistic viscous hydrodynamics approach [1]. For the initial non-equilibrium evolution phase, we employ A MultiPhase Transport model that explicitly includes event-by-event fluctuations in the number and positions of the participating nucleons as well as of the produced partons with subsequent parton transport. The ensuing near-equilibrium evolution of quark-gluon and hadronic matter is modeled within the (2+1)D relativistic viscous hydrodynamics. (1) We probe the role of parton dynamics in generating and maintaining the spatial anisotropy in the pre-equilibrium phase. Substantial spatial eccentricities $\varepsilon_n$ are found to be generated in the process of parton production from initial NN collisions. (2) For ultra-central heavy-ion collisions, the model is able to explain qualitatively the unexpected hierarchy of the flow coefficients $v_n(p_T)~(n=2-6)$ observed at LHC. (3) We find that the results for $v_n(p_T)$ are rather insensitive to the variation (within a range) of the time of switchover from AMPT parton transport to hydrodynamic evolution. (4) The usual Grad and the recently proposed Chapman-Enskog-like single-particle distribution functions are found to give very similar results for $v_n(p_T)~(n=2-4)$. (5) The model describes well both the RHIC and LHC data for $v_n(p_T)$ at various centralities, with a constant shear viscosity to entropy density ratio 0.08 and 0.12, respectively. (6) The event-by-event distributions of $v_{2,3}$ are in good agreement with the LHC data for mid-central collisions. The linear response relation $v_n = k_n \varepsilon_n$ is found to be true for $n=2,3$, except at large values of $\varepsilon_n$, where a larger value of $k_n$ is required, suggesting a small admixture of positive nonlinear response even for $n=2,3$.
[1] R.S. Bhalerao, A. Jaiswal, S. Pal, arXiv:1503.03862
Primary author
Rajeev Bhalerao
(TIFR)
Co-authors
Amaresh Jaiswal
(GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt)
Subrata Pal
(Tata Institute of Fundamental Research, Mumbai, India)
