Measurement of charm production in antineutrino charged-current interactions

During the years 1994-1997, the emulsion target of the CHORUS detector was exposed to the wide-band neutrino beam of the CERN SPS collecting about 106 neutrino interactions. A measurement of ν-bar μ-induced charm production is performed by using the presence of a 5% ν-bar μ component in the νμ beam. The measurement takes advantage of the capability to observe the decay topology in the emulsion. The analysis is based on a sample of charged-current interactions with at least one identified muon. About 100-bar 000 were located in the emulsion target and fully reconstructed. By requiring a positive muon charge as determined by the CHORUS muon spectrometer, 32ν-bar μ-induced charm events were observed with an estimated background of 3.2 events. At an average antineutrino energy in the neutrino beam of 18 GeV, the charm production rate induced by antineutrinos is measured to be σ(ν-bar μN->μ+c-bar X)/σ(ν-bar μN->μ+X)=(5.0-0.9+1.4(stat)+/-0.7(syst))%. The ratio between neutral and charged charm production rates in this process is (2.6-1.0+1.7(stat)+/-0.8(syst)). The charm production rate as a function of the antineutrino energy is found to be in good agreement with previous results derived from di-lepton data