Measurement of topological muonic branching ratios of charmed hadrons produced in neutrino-induced charged-current interactions

From 1994 to 1997, the emulsion target of the CHORUS detector was exposed to the wideband neutrino beam of the CERN SPS. In total about 100 000 charged-current neutrino interactions were located in the nuclear emulsion target and fully reconstructed. From this sample of events based on the data acquired by new automatic scanning systems, 2013 charm-decay events were selected by a pattern recognition program. They were confirmed as decays through visual inspection. Based on these events, the effective branching ratio of charmed particles into muons was determined to be B¯μ=[7.3±0.8(stat)±0.2(syst)]×10−2. In addition, the muonic branching ratios are presented for dominating charm-decay topologies. Normalization of the muonic decays to charged-current interactions provides σμ−μ+/σcc=[3.16±0.34(stat)±0.09(syst)]×10−3. Selecting only events with visible energy greater than 30 GeV gives a value of B¯μ that is less affected by the charm production threshold and quasi-elastic Λc+ production. Combining this value with the current average of B¯μ×|Vcd|2 at the leading order yields the value of |Vcd|LO=0.236±0.016.