Phenomenological bound on the viscosity of the hadron resonance gas

We explore some phenomenological issues during calculations of transport coefficients for hadronic matter, produced in the experiments of heavy ion collisions. Here, we use an ideal hadron resonance gas model to demonstrate the issues. On the basis of dissipation mechanism, the hadronic zoo is classified into resonance and nonresonance members who participate in dissipation via strong decay and scattering channels, respectively. Imposing our phenomenological restriction, we are able to provide a rough upper and lower bound estimations of transport coefficients. Interestingly, we find that our proposed lower limit estimation for shear viscosity to entropy density ratio is a little larger than its quantum lower bound. By taking a simple example, we demonstrate how our proposed restriction helps to tune any estimation of transport coefficients within its numerical band, proposed by us.