Hadron mass spectrum and the shear viscosity to entropy density ratio of hot hadronic matter

摘要

Lattice calculations of the QCD trace anomaly at temperatures T <160 MeV have been shown to matchnhadron resonance gas model calculations, which include an exponentially rising hadron mass spectrum. In thisnpaper we perform a more detailed comparison of the model calculations to lattice data that confirms the neednfor an exponentially increasing density of hadronic states. Also, we find that the lattice data is compatible with anhadron density of states that goes as ρ(m) ∼ mn−a exp(m/TH) at large m with a > 5/2 (where TH ∼ 167 MeV).nWith this specific subleading contribution to the density of states, heavy resonances are most likely to undergontwo-body decay (instead of multiparticle decay), which facilitates their inclusion into hadron transport codes.nMoreover, estimates for the shear viscosity and the shear relaxation time coefficient of the hadron resonancenmodel computed within the excluded volume approximation suggest that these transport coefficients are sensitivento the parameters that define the hadron mass spectrum.