Dilepton and trilepton production by neutrinos in Gargamelle at CERN SPS energies

Abstract

We report on a search for ν μ N → μ −e −X and ν μ N → μ −e +e −X events in Gargamelle at CERN Super Proton Synchrotron (SPS) energies. Ten μ −e − events were found with p e − > 0.5 GeV/ c and p μ − > 4.5 GeV/ c (seven of these events have p e − > 0.8 GeV/ c). The rate relative to the charged-current events is (6.7 ± 3.9) × 10 −4, and to the opposite-sign dileptons 0.20 ± 0.11. Some characteristics of the μ −e − events are compared with μ −e + and charged-current events. Three ν μ N → μ −e +e −X events were observed with p e ± > 0.3 GeV/ c, p μ − > 4.5 GeV/ c, and m e +e − > m π 0 . The rate of these events relative to the charged-current events is (3.1 ± 1.9) × 10 −4.