Enhanced production of $\psi \left(2S\right)$ mesons in heavy ion collisions

I study the production of a $\psi \left(2S\right)$ meson in heavy ion collisions. I evaluate Wigner functions for the $\psi \left(2S\right)$ meson using both Gaussian and Coulomb wave functions, and investigate the wave function dependence in the $\psi \left(2S\right)$ meson production by recombination of charm and anticharm quarks. The enhanced transverse momentum distribution of $\psi \left(2S\right)$ mesons compared to that of $J/\psi$ mesons, originated from wave function distributions of the $\psi \left(2S\right)$ and $J/\psi$ meson in momentum space, provides a plausible explanation for the recent measurement of the nuclear modification factor ratio between the $\psi \left(2S\right)$ and $J/\psi$ meson.

Figure 1

$2\pi p_T{d}^2{N}_{\psi }/d^2{p}_T$ of charmonia produced form charm and anticharm quarks by recombination for $\sqrt{s_{NN}}=200$ GeV at RHIC (a) and for $\sqrt{s_{NN}}=2.76$ TeV at LHC (b). The ratio of $p_T$ spectrum between $\psi \left(2S\right)$ and prompt $J/\psi$ mesons is shown in the inset.