Heavy baryon/meson ratios in relativistic heavy ion collisions

TL;DR

This paper investigates heavy baryon/meson ratios in relativistic heavy ion collisions using a quark coalescence model, highlighting the impact of diquarks and heavy quark mass on these ratios and their momentum dependence.

Contribution

It introduces a detailed coalescence model including diquark effects and decay contributions, providing new predictions for heavy baryon/meson ratios in heavy ion collisions.

Findings

Ratios are significantly larger than thermal and PYTHIA models.

Diquarks increase the ratios by a factor of about 1.6.

The momentum dependence varies with heavy quark mass and diquark presence.

Abstract

Heavy baryon/meson ratios $\Lambda_c/D^0$ and $\Lambda_b/\bar{B}^0$ in relativistic heavy ion collisions are studied in the quark coalescence model. For heavy baryons, we include production from coalescence of heavy quarks with free light quarks as well as with bounded light diquarks that might exist in the strongly coupled quark-gluon plasma produced in these collisions. Including the contribution from decays of heavy hadron resonances and also that due to fragmentation of heavy quarks that are left in the system after coalescence, the resulting $\Lambda_c/D^0$ and $\Lambda_b/\bar{B}^0$ ratios in midrapidity ($|y|\le 0.5$) from central Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV are about a factor of five and ten, respectively, larger than those given by the thermal model, and about a factor of ten and twelve, respectively, larger than corresponding ratios in the PYTHIA model for $pp$ collisions. These ratios are reduced by a factor of about 1.6 if there are no diquarks in the quark-gluon plasma. The transverse momentum dependence of the heavy baryon/meson ratios is found to be sensitive to the heavy quark mass, with the $\Lambda_b/\bar{B}^0$ ratio being much flatter than the $\Lambda_c/D^0$ ratio. The latter peaks at the transverse momentum $p_T^{} \simeq 0.8$ GeV but the peak shifts to $p_T^{} \simeq 2$ GeV in the absence of diquarks.