The recent results of the relativistic heavy ion collider suggest that, just above the phase transition point, even though the effect of quark confinement vanishes, quarks and gluons do not immediately become a quark gluon plasma, that is, the mesonic correlation of a quark and an anti-quark still exists. Accordingly, we expect that the effect of the (quasi) bound state, like a meson, is important whether the effect of confinement exists or not, in the neighborhood of the phase transition point. Therefore, in this report, we present the effect of meson loops in the SU(2) Nambu-Jona-Lasinio (NJL) model. Especially, comparing our result with the mean field approximation, we investigate the change of the chiral phase transition curve.
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