Hadron gas with repulsive mean field

Abstract

We study the QCD equation of state, and fluctuations of baryon number and strangeness using the hadron resonance gas model with repulsive mean field. We find that including both the predicted but not observed resonances, a.k.a. missing states, and the repulsive mean field into the resonance gas model leads to better description of the lattice results. The repulsive mean field is particularly important for the higher order baryon number fluctuations.

Hadron resonance gas with repulsive interactions and baryon rich matter

“…Within this approach one can estimate the difference between the second order fluctuations and correlations of conserved charges and the fourth and sixth order fluctuations and correlations. The model can explain these differences reasonably well [7] if one assumes that only ground state octet and decuplet baryons are affected by the repulsive interactions.…”

“…the mean-field is repulsive. In what follows we will use the value K = 450 MeV/fm 3 , which is consistent withb 2 (T ) at the highest temperatures [7]. It is straightforward to generalize the mean-field approach described above to a multicomponent system, e.g.…”

“…Furthermore, M is the nucleon mass and K 2 (x) is the Bessel function of second kind. Using the parameterization of the S-matrix in terms of the phase shifts and their numerical values the virial coefficient b 2 (T ) can be calculated, and it turns out that b 2 (T ) is negative [7]. For the comparison with the mean-field approach discussed below it is convenient to write the above expression for the pressure in the following form…”

“…It is straightforward to generalize the mean-field approach described above to a multicomponent system, e.g. HRG if one assumes that the repulsive mean-field is the same for all baryons [7]. Within this approach one can estimate the difference between the second order fluctuations and correlations of conserved charges and the fourth and sixth order fluctuations and correlations.…”

“…As in Ref. [7] we only include the repulsive mean-field for the ground state octet and decuplet baryons. We will consider temperatures up to 170 MeV and moderate values of the baryon chemical potential µ B ≤ 400 MeV.…”