Multi-lepton production at high transverse momentum at HERA 

                   ZEUS Collaboration

                      Abstract

A search for events containing two or more high-transverse momentum 
isolated leptons has been performed in ep collisions with the ZEUS 
detector at HERA using the full collected data sample, corresponding to an 
integrated luminosity of 480 pb^{-1}. The number of observed events has 
been compared with the prediction from the Standard Model, searching for 
possible deviations, especially for multi-lepton events with invariant 
mass larger than 100 GeV. Good agreement with the Standard Model has been 
observed. Total and differential cross sections for di-lepton production 
have been measured in a restricted phase space dominated by photon-photon 
collisions.