Invariant mass spectra of $\mu^+\mu^-$ (top) and $e^+e^-$ (bottom) pairs in ultraperipheral Pb-Pb collisions. The solid and dotted lines represent the background (exponential) and peak (Crystal Ball) fit components, respectively. The bremsstrahlung tail in the $e^+e^-$ spectrum is reproduced in simulation. The mass resolution is better than 1%.