Parity doubling of nucleons and Delta baryons across the deconfinement phase transition
D. De Boni, G. Aarts, C. Allton, S. Hands, B. Jaeger, C. Praki, J.I. Skullerud
At zero temperature the negative-parity ground states of the nucleon and delta baryons are non-degenerate
with the positive-parity partners due to spontaneous breaking of chiral symmetry. However, chiral symmetry is
expected to be restored at sufficiently high temperature, in particular when going from
the hadronic to the quark-gluon plasma (QGP) phase. This would imply that channels with opposite parity
become degenerate. We study the nucleon (spin 1/2) and Delta (spin 3/2) baryons in both
parity sectors using lattice QCD. The range of temperatures spans both the hadronic and QGP phases. Using the
FASTSUM anisotropic $N_f = 2 + 1$ ensembles, we analyze the correlation functions and the
spectral functions using respectively exponential fits and the Maximum Entropy Method.
We find clear evidence of in-medium effects in the hadronic phase, especially for the negative-parity ground state, and of parity doubling in the QGP phase.