Observation of a visible charmed particle decay in neutrino interactions

In a sample of 250 semileptonic charmed particle decays (ν/sub μ/ + Neon → μ- + e+ + ... events), one clear event is found where the e+ does not come directly from the ν interaction vertex but from a decay point 1.1 cm downstream of the vertex. This event is interpreted as a visible charmed particle decay: into an e+ and a positive and a negative charged track. The observation of a visible charm decay in the sample is consistent with what is expected if the charm lifetime were of the order 5 x 10-13 sec. 5 references