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HK: Physik der Hadronen und Kerne

HK 26: Theory IV

HK 26.7: Talk

Wednesday, March 10, 2004, 12:30–12:45, D

The Quark-Mass Dependence of T_C in QCD: Working up from m=0 or down from m=∞ ? — •Dirk Röder, Adrian Dumitru, and Jörg Ruppert — JWG-Universität, Robert-Mayer-Str.10, D-60054 Frankfurt am Main

We analyze the dependence of the QCD transition temperature on the quark (or pion) mass. We find that a linear sigma model, which links the transition to chiral symmetry restoration, predicts a much stronger dependence of T_c on m_π than seen in present lattice data for m_π∼^>0.4 GeV. On the other hand, working down from m_π=∞, an effective Lagrangian for the Polyakov loop requires only small explicit symmetry breaking, b₁∼exp(−m_π), to describe T_c(m_π) in the above mass range. Physically, this is a consequence of the flat potential (large correlation length) for the Polyakov loop in the three-color pure gauge theory at T_c. We quantitatively estimate the end point of the line of first order deconfining phase transitions: m_π≃4√σ≃1.7 GeV for N_f=3.