Medium effects and parity doubling of hyperons across the deconfinement phase transition

Preprint number: CP3-Origins-2017-42 DNRF90
Authors: Gert Aarts (Swansea University), Chris Alton (Swansea University), Davide De Boni (Swansea University), Simon Hands (Swansea University), Benjamin Jaeger (CP3-Origins & DIAS), Chrisanthi Praki (Swansea University), and Jon-Ivar Skullerud (Maynooth University & Trinity College Dublin)
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We analyse the behaviour of hyperons with strangeness S = −1,−2,−3 in the
hadronic and quark gluon plasma phases, with particular interest in parity doubling and
its emergence as the temperature grows. This study uses our FASTSUM anisotropic
N_f = 2+1 ensembles, with four temperatures below and four above the deconfinement
transition temperature, T_c . The positive-parity groundstate masses are found to be largely
temperature independent below T_c , whereas the negative-parity ones decrease consider-
ably as the temperature increases. Close to the transition, the masses are almost degener-
ate, in line with the expectation from chiral symmetry restoration. This may be of interest
for heavy-ion phenomenology. In particular we show an application of this effect to the
Hadron Resonance Gas model. A clear signal of parity doubling is found above T_c in all
hyperon channels, with the strength of the effect depending on the number of s-quarks in
the baryons.