It is expected that nucleons and their parity partners become degenerate when chiral symmetry is restored. We investigate this question in the context of the thermal transition from the hadronic phase to the quark-gluon plasma, using lattice QCD simulations with $N_f=2+1$ flavors. We observe a clear sign of parity doubling in the quark-gluon plasma. Besides, we find that the nucleon ground state is, within the uncertainty, largely independent of the temperature, whereas temperature effects are substantial in the negative-parity ($N^{*}$) channel, already in the confined phase.

• Received 16 February 2015

DOI:https://doi.org/10.1103/PhysRevD.92.014503