Deconfining Chiral Transition in QCD on the Lattice

The deconfining chiral transition in finite-temperature QCD is studied on the lattice using Wilson quarks. After discussing the nature of chiral limit with Wilson quarks, we first study the case of two degenerate quarks $N_F=2$, and find that the transition is smooth in the chiral limit on both $N_t=4$ and 6 lattices. For $N_F=3$, on the other hand, clear two state signals are observed for $m_q \simm{<} 140$ MeV on $\nt=4$ lattices. For a more realistic case of $N_F=2+1$, i.e.\ two degenerate u and d-quarks and a heavier s-quark, we study the cases $m_s \simeq 150$ and 400 MeV with $m_u = m_d \simeq 0$: In contrast to a previous result with staggered quarks, clear two state signals are observed for both cases, suggesting a first order QCD phase transition in the real world.