Elliptic flow as a probe for $\psi(2S)$ production mechanism in   relativistic heavy ion collisions
  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. 
Baoyi Chen
nucl-th