出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：Events with at least two high transverse momentum leptons (electrons or muons) are studied using the H1 and ZEUS detectors at HERA with an integrated luminosity of 0:94 fb1. The observed numbers of events are in general agreement with the Standard Model predictions. Seven di- and tri-lepton events are observed in e+p collision data with a scalar sum of the lepton transverse momenta above 100 GeV, while 1:940:17 events are expected. Such events are not observed in ep collisions for which 1:190:12 are predicted. Total visible and differential di-electron and di-muon photoproduction cross sections are extracted in a restricted phase space dominated by photon-photon collisions.
