Importance of the Bulk Viscosity of QCD in Ultrarelativistic Heavy-Ion Collisions

Abstract

We investigate the consequences of a nonzero bulk viscosity coefficient on the transverse momentum spectra, azimuthal momentum anisotropy, and multiplicity of charged hadrons produced in heavy ion collisions at LHC energies. The agreement between a realistic 3D hybrid simulation and the experimentally measured data considerably improves with the addition of a bulk viscosity coefficient for strongly interacting matter. This paves the way for an eventual quantitative determination of several QCD transport coefficients from the experimental heavy ion and hadron-nucleus collision programs.

Dynamical versus equilibrium properties of the QCD phase transition: A holographic perspective

“…In [116,117], effects from the bulk viscosity transport coefficient, ζ, were included in event-by-event hydrodynamics and state-of-the-art hydrodynamic models [101,113] have shown that this coefficient is an important ingredient in the description of heavy ion experimental data. For instance, in the calculations performed in [101] a profile for the bulk viscosity peaking at the crossover allowed for a simultaneous agreement with experimental data for different physical observables.…”

Event-by-EventHydrodynamics+JetEnergy Loss: A Solution to theRAA⊗vNoronha-Hostler1, Betz2, Noronha3 et al. 2016Phys. Rev. Lett.11661573View full textAdd to dashboardCite

“…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.…”

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.…”