Strange Baryons in a Hot and Dense Medium within the Nambu–Jona-Lasinio Model

Abstract

The understanding of the chiral phase transition is one of the challenges of present day nuclear physics. Lattice gauge calculation are still not advanced enough to provide reliable information on how this transition takes place. Using a phenomenological approach, an extended version of the Nambu-Jona-Lasinio model, we study how baryons behave at high densities and temperatures. In this model baryons are diquark-quark bound states. Their properties can be calculated using parameters which are adjusted to known vacuum physics. First a description of the diquarks in a dense and hot medium is presented. Then we introduce the formalism for the baryons based on the Faddeev equation using the so-called “static approximation” which finally gives a Bethe-Salpeter equation in the diquarks-quarks channel. By identifying the baryons with the bound states, we can obtain a description of their properties. In particular, we obtain the right mass spectrum for the proton, Λ, Ξ, and Σ at T=0 and μ=0. We extend the formalism to finite temperature and density to obtain a description of the mass change of these baryons in the medium.