Elliptic flow as a probe for $\psi(2S)$ production mechanism in relativistic heavy ion collisions

TL;DR

This paper investigates how the elliptic flow of $ ext{psi}(2S)$ particles in heavy ion collisions can reveal their production mechanisms, distinguishing between regeneration from charm quarks and transitions from $J/ ext{psi}$ due to QGP effects.

Contribution

It proposes using the elliptic flow of $ ext{psi}(2S)$ as a sensitive observable to differentiate production mechanisms in relativistic heavy ion collisions.

Findings

Regenerated $ ext{psi}(2S)$s inherit large flow from charm quarks.

Elliptic flow of $ ext{psi}(2S)$ exceeds that of $J/ ext{psi}$ if regenerated.

Flow similarity indicates transition from $J/ ext{psi}$ to $ ext{psi}(2S)$.

Abstract

I discuss the elliptic flows of $\psi(2S)$ with different production mechanisms in $\sqrt{s_{NN}}=2.76$ TeV Pb-Pb collisions. If the final $\psi(2S)$s are mainly from the recombination of uncorrelated charm and anticharm quarks at $T\approx T_c$, charm and anticharm quarks will carry large collective flows of the bulk medium, which will be inherited by the regenerated $\psi(2S)$s. This indicates a larger elliptic flow of $\psi(2S)$ than that of $J/\psi$ which can be regenerated at $T\ge T_c$, $v_2^{\psi(2S)}>v_2^{J/\psi}$. However, if the final $\psi(2S)$s are mainly from the transitions of $J/\psi\rightarrow \psi(2S)$ caused by the color screening of QGP, its elliptic flow should be close to the elliptic flow of $J/\psi$, $v_2^{\psi(2S)}\sim v_2^{J/\psi}$. Therefore, $\psi(2S)$ elliptic flow is a sensitive probe for its production mechanisms in relativistic heavy ion collisions.