# Nuclear Theory Seminars at Texas A&M: Fall 2009

Location: Cyclotron Building (434), Seminar Room

Friday, October 2, 4:00pm
Nuclear Seminar
Min He (Cyclotron Institute Texas A&M)

"Susceptibilites and QCD chiral phase transition"

Abstract

Low energy in-vacuum QCD exhibits two remarkable
features, namely the quark confinement and the spontaneous/dynamical
chiral symmetry breaking. At sufficiently high temperature and/or
baryon density, quarks are expected to de-confine from hadrons and
probably at the same time, the broken chiral symmetry gets restored.
This is the so-called QCD phase transition that is relevant to the
evolution of very early Universe after the "Big Bang" and is being
explored via relativistic heavy ion collisions in terrestrial
laboratories (little bangs).

In this talk, we  investigate some aspects of the chiral transition
by studying two susceptibilities. We derive model-independent closed
integral formulae for the chiral susceptibility and the quark-number
susceptibility, which express the latter in terms of QCD dressed
two- and three-point functions. These are then illustrated by model
calculations in the framework of Dyson-Schwinger and Bethe-Salpeter
equations. Some qualitative/quantitative characteristics concerning
QCD chiral transition are identified: 2nd/1st -order phase
transition, crossover, critical end point and phase diagram on the
T-$\mu$ plane. Comparison with results from lattice simulations and
some other phenomenological model studies will also be discussed.

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