Charm Degrees of Freedom in Quark Gluon Plasma

TL;DR

This paper reexamines lattice QCD data to reveal that charm degrees of freedom in quark-gluon plasma include not only quark-like excitations but also significant contributions from meson and baryon-like states up to 1.2 times the crossover temperature, with charm quark quasiparticles dominating above that.

Contribution

It demonstrates that open-charm meson and baryon-like excitations significantly contribute to charm degrees of freedom below 1.2 T_c, extending understanding beyond quark-like excitations.

Findings

Charm degrees of freedom include meson and baryon-like states up to 1.2 T_c.

Charm quark quasiparticles dominate above 1.2 T_c.

Deconfinement of charm occurs around T_c, with fractional baryonic charges appearing.

Abstract

Lattice QCD studies on fluctuations and correlations of charm quantum number have established that deconfinement of charm degrees of freedom sets in around the chiral crossover temperature, $T_c$, i.e. charm degrees of freedom carrying fractional baryonic charge start to appear. By reexamining those same lattice QCD data we show that, in addition to the contributions from quark-like excitations, the partial pressure of charm degrees of freedom may still contain significant contributions from open-charm meson and baryon-like excitations associated with integral baryonic charges for temperatures up to $1.2~ T_c$. Charm quark-quasiparticles become the dominant degrees of freedom for temperatures $T>1.2~ T_c$.