$J/\psi$ regeneration in a hadron gas: an update

TL;DR

This paper investigates the interactions of charmed mesons in a hadron gas phase after heavy ion collisions, updating previous models by including strange mesons and exotic resonances, and finds minimal impact on $J/\psi$ abundance.

Contribution

It introduces new reaction channels involving strange mesons and exotic resonances, providing a more comprehensive calculation of $J/\psi$ production and absorption in the hadron gas.

Findings

Interactions in the hadron gas do not significantly alter $J/\psi$ abundance.

No evidence of charmonium suppression or regeneration in the hadronic phase.

Updated cross sections include effects of exotic charmonium resonances.

Abstract

In heavy ion collisions after the quark-gluon plasma there is a hadronic gas phase. Using effective Lagrangians we study the interactions of charmed mesons which lead to $J/\psi$ production and absorption in this gas. We update and extend previous calculations introducing strange meson interactions and also including the interactions mediated by the recently measured exotic charmonium resonances $Z(3900)$ and $Z(4025)$. These resonances open new reaction channels for the $J/\psi$, which could potentially lead to changes in its multiplicity. We compute the $J/\psi$ production cross section in processes such as $D_{(s)}^{(*)} + \bar{D}^{(*)} \to J/\psi + (\pi, \rho, K, K^{\ast})$ and also the $J/\psi$ absorption cross section in the corresponding inverse processes. Using the obtained cross sections as input to solve the rate equation, we conclude that the interactions in the hadron gas phase do not significantly affect the $J/\Psi$ abundance. In other words, there is neither a charmonium suppression nor charmonium regeneration from light mesons in the hadronic phase.