Abstract
This Letter reports on a study of trimuon events induced by neutrino interactions in the CHORUS calorimeter exposed to the CERN SPS wide-band νμ beam. Among the multimuon events produced in the calorimeter, 42 μ−μ−μ+ events were selected and their kinematical properties investigated. In the past, several groups collected a sample of about one hundred events of this type but their source was largely unknown. Taking advantage of experimental data presently available on the production and muonic branching ratios of light neutral mesons and resonances, we make absolute predictions for the expected rates in our experiment. Detailed Monte Carlo simulations described in this article show that more than half of the trimuon events can be attributed to this source. Muons from π− and K− decays in charm dimuon events are responsible for an additional ≈25% contribution to the total μ−μ−μ+ rate. The remaining 25% of events are likely to come from the internal bremsstrahlung of virtual photons into a muon pair. Associated-charm production with subsequent decays of both charmed particles into muons is a negligible source of trimuon events.
Highlights
Trimuon production in neutrino interactions was first observed at FNAL [1] and at CERN [2] more than 25 years ago
Detailed Monte Carlo (MC) simulations, including rare decays of light neutral mesons and resonances (η, η, ρ, ω and φ) are used, since we believe that they constitute a substantial fraction of the observed event rate
It is expected that the decays of light neutral mesons and resonances, muonic decays of charmed particles with an additional pion or kaon decay, and internal bremsstrahlung contribute to trimuon production
Summary
Trimuon production in neutrino interactions was first observed at FNAL [1] and at CERN [2] more than 25 years ago. The total number of dimuon events observed with the selections equivalent to those used for trimuons is 15111 for μ−μ+, 2107 for μ−μ− and 66 for μ+μ+ sign combinations.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have