PRODUCTION OF CHARMED MESONS IN NEUTRINO INTERACTIONS IN HYDROGEN

Production of charmed mesons has been observed in neutrino-hydrogen interactions in 285 000 photographs of BEBC exposed to the CERN wide-band neutrino beam. In ∼ 6000 charged current events, two events have been found each giving a three-constraint kinematical fit with production of only one strange particle, namely a K-, which is identified by its characteristic reaction K-p→Σ-π+. These events are thus examples of ΔS=-ΔQ reactions corresponding to charm production on a valence quark. For both events the effective mass of a (K- + pions) system is equal to the D0(1863) mass while the effective mass of this system plus a π+ is equal to the D*+(2009) mass. The mass difference ΔM=M(D*+)-MD0 is 145.2 ± 0.6 MeV. The first event is interpreted as νp→μ-pD*+ and the second as νp→μ-pD*+π+π-, both with D*+→D0π+. The rate of inclusive D*+ production has been estimated for all events by assuming that each negative track in turn is a K- and using the fact that the error on ΔM is small. It is found that the cross section σ(νp→μ-D*++anything) relative to σ(νp→μ- + anything), above the D* threshold, is (4.1 ± 2.4)%. © 1979.