Figure 1

Unlike-sign dimuon invariant mass distributions for six centrality classes for $\pt < 15$ Gev/$c$ in the Pb-p configuration. The solid blue curves correspond to a fit based on a pseudo-Gaussian functionfor the $\jpsi$ and $\psi(\rm{2S})$ signals (see text) and an exponential multiplied by a second order polynomial function for the background. The red dashed lines represent the fitted signal function.