Speaker
Thomas Schaefer
(N)
Description
We study the effects of bulk viscosity on $p_T$ spectra and
elliptic flow in heavy ion collisions. For this purpose we compute
the dissipative correction $\delta f$ to the single particle
distribution functions in leading-log QCD, and in kinetic
models of a hadronic resonance gas. We find that for a near
conformal fluid the bulk viscosity is suppressed by two powers
of the conformal breaking parameter, but the viscous correction
to the spectra is only suppressed by the first power. This
implies that bulk viscous corrections to flow profiles are
typically small, but corrections to the spectra can be significant.
From an analysis of the spectra at RHIC and LHC we find that the
bulk viscosity at freezeout cannot be large, $\zeta/s<0.05$. We
also find, however, that a non-zero bulk viscosity improves
the description of the hadrochemistry of flow, for example
the splitting between the $v_2(p_T)$ of protons and pions.
Author
Thomas Schaefer
(N)
