Speaker
Description
In this work, the qualitative impact of the net baryochemical potential dependence of the shear viscosity to entropy density ratio $\eta/s$ in hydrodynamical simulations is studied. The effect of a predicted non-constant $\eta/s(\mu_B)$ is largely unexplored in hydrodynamic simulations. Previous studies focus only on a temperature dependence[1-3] or even only a constant effective shear viscosity[4]. This work addresses this issue by studying qualitatively the effect of a generalized $\eta/s(T,\mu_B)$ in the novel hybrid approach SMASH-vHLLE, composed of the hadronic transport approach SMASH[5] and the (3+1)d viscous hydrodynamic code vHLLE[6]. In order to reduce the bias of the result on the equation of state used in the hydrodynamic part of the model, $\eta/s$ is parameterized directly in the energy density and baryon number density. The parameterization takes into account the constraints of matching to the transport coefficients in the hadronic phase[7], as well as of recent Bayesian analysis results. This work compares the impact of the density dependence for different system sizes and energies and constrains the behaviour of $\eta/s(T,\mu_B)$ by ruling out regions of the parameter space. This is achieved by comparing the observables with experimental results in the RHIC - BES region $\sqrt{s_{NN}}$= 4.3 - 17.3 GeV, as the effect of this generalisation is especially relevant for intermediate collision energies, for which the system is in equilibrium for a relevant amount of time, but the net baryochemical potential does not vanish.
References
[1] J. E. Parkkila, A. Onnerstad, F. Taghavi, C. Mordasini, A. Bilandzic und D. J. Kim, New constraints for QCD matter from improved Bayesian parameter estimation in heavy-ion collisions at LHC, 2021.
[2] D. Everett u. a. (JETSCAPE), „Phenomenological constraints on the transport properties of QCD matter with data-driven model averaging“, Phys. Rev. Lett. 126, 242301 (2021).
[3] D. Everett u. a. (JETSCAPE), „Multisystem Bayesian constraints on the transport coefficients of QCD matter“, Phys. Rev. C103,054904 (2021).
[4] J. Auvinen, J. E. Bernhard, S. A. Bass und I. Karpenko, „Investigating the collision energy dependence of $\eta$/s in the beam energy scan at the BNL Relativistic Heavy Ion Collider using Bayesian statistics“, Phys. Rev. C97, 044905 (2018).
[5] https://github.com/smash-transport/smash
[6] https://github.com/yukarpenko/vhlle
[7] J.-B. Rose, J. M. Torres-Rincon, A. Schäfer, D. Oliinychenko and H. Petersen, "Shear viscosity and resonance lifetimes in the hadron gas", Nuclear Physics A 982, 807-810 (2019).
