Bulk viscosity-driven suppression of shear viscosity effects on the flow harmonics at energies available at the BNL Relativistic Heavy Ion Collider

Abstract

The interplay between shear and bulk viscosities on the flow harmonics, v n 's, at RHIC is investigated using the newly developed relativistic 2+1 hydrodynamical code v-USPhydro that includes bulk and shear viscosity effects both in the hydrodynamic evolution and also at freeze-out. While shear viscosity is known to attenuate the flow harmonics, we find that the inclusion of bulk viscosity decreases the shear viscosity-induced suppression of the flow harmonics bringing them closer to their values in ideal hydrodynamical calculations. Depending on the value of the bulk viscosity to entropy density ratio, ζ/s, in the quark-gluon plasma, the bulk viscosity-driven suppression of shear viscosity effects on the flow harmonics may require a re-evaluation of the previous estimates of the shear viscosity to entropy density ratio, η/s, of the quark-gluon plasma previously extracted by comparing hydrodynamic calculations to heavy ion data.

Event-by-EventHydrodynamics+JetEnergy Loss: A Solution to theRAA⊗vNoronha-Hostler1, Betz2, Noronha3 et al. 2016Phys. Rev. Lett.Self Cite11861573View full textAdd to dashboardCite

“…The soft sector is modeled via event-by-event hydrodynamic simulations performed using the v-USPhydro code [61][62][63][64] while the hard sector is described using the energy loss framework developed in [36,65,66]. We show that the positive contribution from low p T v 2 fluctuations overwhelms the small, negative contributions from event plane fluctuations, which in turn leads to an overall enhancement of high p T elliptic flow in comparison to previous calculations.…”

“…For simplicity, e↵ects from the temperature dependence of ⌘/s in the hadronic [72][73][74] or in the QGP phase [75] are neglected here and, thus, we set ⌘/s to be a constant. Also, in this first study bulk viscosity [61,62,76] is set to zero. The initial time for all the hydrodynamic simulations was 0.6 fm and we used the lattice-based equation of state EOS S95n-v1 [77] and an isothermal Cooper-Frye [78] freezeout with freeze-out temperature T F = 120 MeV for MCKLN and T F = 130 for MCGlauber.…”

“…Hydrodynamic evolution. The expanding QGP is modeled through event-by-event simulations performed using the 2+1 (i.e., boost invariant) viscous relativistic hydrodynamics code called v-USPhydro [61][62][63][64]. vUSPhydro accurately [68] solves the energy-momentum conservation equations and the equations of motion for the dissipative currents using the Lagrangian formulation of hydrodynamics encoded in the Smoothed Particle Hydrodynamics (SPH) algorithm [69,70].…”

Temperature dependent transport coefficients in a dynamical holographic QCD model

“…The near phase transition enhancement of bulk viscosity corresponds to the peak of trace anomaly around T c , which shows the equation of state is highly nonconformal [36,37] around phase transition. Recent studies [38,39] show that bulk viscosity could also have important effects on hydrodynamic simulations of HIC: it would increase the flow harmonics(such as v 2 and v 3 ) while shear viscosity decreases them.…”

Bulk viscosity for pion and nucleon thermal fluctuation in the hadron resonance gas model

“…[5] exposes the possibility of divergence of ζ near the transition temperature. In recent times, different phenomenological investigations [6][7][8][9][10][11][12][13][14][15][16][17][18] demonstrated that bulk viscosity can have a non-negligible effect on heavy ion observables, where the values of ζ/s in Ref. [18] is assumed to be quite large.…”