  We derive exact predictions for universal scaling exponents and scaling
functions associated with the statistics of maximum velocities vm during
avalanches described by the mean field theory of the interface depinning
transition. In particular, we find a robust power-law regime in the statistics
of maximum events that can explain the observed distribution of the peak
amplitudes in acoustic emission experiments of crystal plasticity. Our results
are expected to be broadly applicable to a broad range of systems in the
mean-field interface depinning universality class, ranging from magnets to
earthquakes.
