Mass shift of charmonium states in p¯A collision

The masses of the low lying charmonium states, namely, the $J/\Psi$, $\Psi \left(3686\right)$, and $\Psi \left(3770\right)$ are shifted downwards due to the second order Stark effect. In $\overline{p}+\text{Au}$ collisions at 6–10 GeV we study their in-medium propagation. The time evolution of the spectral functions of these charmonium states is studied with a Boltzmann–Uehling–Uhlenbeck (BUU) type transport model. We show that their in-medium mass shift can be observed in the dilepton spectrum. Therefore, by observing the dileptonic decay channel of these low lying charmonium states, especially for $\Psi \left(3686\right)$, we can gain information about the magnitude of the gluon condensate in nuclear matter. This measurement could be performed at the upcoming PANDA experiment at FAIR.