Like-sign dimuon events produced in narrow-band neutrino and antineutrino beams

Forty seven events of the type v + Fe → μ^? + μ^? + X and nine events of the type $\text{v}\text{+}\text{Fe}\text{→ μ}{}^{\mathrm{+}}\text{+ μ}{}^{\mathrm{+}}\text{+}\text{X}$ have been observed, and zero events with like-sign muons of the opposite sign. Most of the observed events can be attributed to the background of normal charged current events, in which one of the pions or kaons of the hadron shower decays, and so produces a second muon. The remaining events correspond to rates of the order of (3 ± 2) × 10^?4 of those for charged current events. They may very well be due to the hadronic production of a charm-anticharm pair, with subsequent decay of one member of the pair. The observed rates correspond to charm-anticharm pair production in 0.5–1% of the hadron showers. No evidence can be found for a lepton-cascade origin of the observed events.