S-matrix approach to the thermodynamics of hadrons

Pok Man Lo (University of Wroclaw/GSI)

In this talk, I will discuss how the S-matrix formalism can be applied to study the thermal properties of interacting hadrons. The approach allows a consistent treatment of broad resonances and purely repulsive channels, while correctly implementing the constraints from chiral perturbation theory. This represents an essential improvement over the standard Hadron Resonance Gas model.

I will apply the method to study (1) the $\rho$-meson and (2) the pion-nucleon system. In the first example the importance of the non-resonant contribution will be demonstrated in correctly describing the soft part of the decay-pion momentum spectra. For the latter case I will describe how the natural implementation of the repulsive forces can help to better understand the lattice-QCD result on the baryon electric charge correlation.

Lastly, I will discuss some recent attempts to include inelastic effects and $N>2$-body scatterings.