Multi-Lepton Events at HERA (H1+ZEUS)

A measurement of multi-lepton events at high transverse momenta is
performed on a data sample collected in $e^\pm p$ collisions with 
the H1 and ZEUS detectors at HERA during the period 1994--2007. This data
sample corresponds to an integrated luminosity of 0.94 
fb$^{-1}$. Yields of di-electron and tri-electron events are measured and
in general a good agreement is found with the Standard Model 
(SM) predictions. Combining the two channels, six events are observed with
a scalar sum of electron transverse momenta, $\sum P_T $, 
greater than 100 GeV, compared to a SM expectation of 3.0 $\pm$ 0.3. Five
of those events are observed in $e^{+}p$ collisions where the 
SM expectation is of 1.8 $\pm$ 0.2, whereas one event is observed in
$e^{-}p$ data for a SM prediction of 1.2 $\pm$ 0.1. The common 
analysis is extended to final states with electrons and muons or
multi-muons, where H1 collaboration previously measured spectacular 
events at large transverse momentum.