# Figure 1

 Opposite-sign invariant mass distributions of selected muon (left panel, for the forward rapidity) and electron (right panel) pairs, for selected multiplicity bins. In the left panel, the distributions are corrected for \acef. The curves show the fit functions for signal, background and combined signal and background (see text for details). In the right panel, the background is evaluated with the event-mixing technique, the overlaid signal is obtained from Monte Carlo (see text for details).