Cross sections for the production of two isolated muons up to high di-muon masses are measured in ep collisions at HERAwith the H1 detector in a data sample corresponding to an integrated luminosity of 71 pb.1 at a centre of mass energy of ¡Ìs = 319 GeV. The results are in good agreement with Standard Model predictions, the dominant process being photon¨Cphoton interactions. Additional muons or electrons are searched for in events with two high transverse momentum muons usingthe full data sample corresponding to 114 pb.1, where data at ¡Ìs = 301 GeV and ¡Ìs = 319 GeV are combined. Both thedi-lepton sample and the tri-lepton sample agree well with the predictions.
Aktas, A., Andreev, V., Anthonis, T., Asmone, A., Stella, B.R. (2004). Muon Pair Production in e-p Collisions at HERA. PHYSICS LETTERS, B583, 28.