# Figure 1

 Fits to invariant mass distributions of opposite-sign dimuons, for 0--90\% \mbox{Xe--Xe} collisions. In the left panel, the result of a fit to the raw invariant mass spectrum is shown, while in the right panel the fit to the same distribution after subtraction of the mixed-event background is presented. The fit curves shown in blue represent the sum of the signal and background shapes, while the red lines correspond to the J/$\psi$ signal and the blue dashed ones to the background (see text for details).