Production of charmed mesons in neutrino interactions in hydrogen

Abstract 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 D 0 (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 ∗+ )−M D 0 is 145.2 ± 0.6 MeV. The first event is interpreted as ν p →μ − pD ∗+ and the second as ν p →μ − pD ∗+ π + π − , both with D ∗+ → D 0 π + . 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(ν p →μ − D ∗+ + anything ) relative to σ ( ν p→ μ − + anything), above the D ∗ threshold, is (4.1 ± 2.4)%.