The Rise and Fall of Baryons

TL;DR

This paper models baryonic contributions to QCD thermodynamics near the phase transition, combining stringy excitations and chiral states, and compares predictions with lattice data to understand baryon behavior at high temperatures.

Contribution

It introduces a finite-temperature string model with new features like string tightening near T_c and a maximum string length, explaining lattice susceptibilities and chiral effects.

Findings

String tightening near T_c improves model accuracy.

Chiral restoration effects influence baryonic susceptibilities.

Possible monopole-quark bound states may explain high-temperature deficits.

Abstract

We discuss the baryonic contribution to QCD thermodynamics near the QCD phase transition, which we split into "stringy excitations" and the "chiral" lowest states. Our finite-$T$ string model for the former component is inspired by the lattice data on static potentials and ideas of string survival even $above$ $T_c$: it is used to explain two sets of baryonic susceptibilities calculated on the lattice by the Bielefeld-BNL group. Two new ingredients of the model are (i) the near-$T_c$ tightening of the strings, and (ii) physical upper limit of the string length. Then we proceed to more subtle effects related to chiral restoration dynamics near $T_c$: we suggest that "melting" of the sigma terms of the lowest nucleon/$\Delta$ masses can explain these susceptibilities. In a discussion, we consider bound monopole-quark states, as a possible explanation to some deficits of contribution at $T=(1-1.4)T_c$.