The CHARON detector—an emulsion/counter hybrid set-up to measure the mean free path of near-elastic pion scattering in nuclear emulsion (white kink) at 2, 3 and 5 GeV/c

White and grey kink events define a special class of soft hadron interactions in nuclear emulsion in which only one track (the scattered hadron) is leaving the interaction vertex. Due to their small and sometimes invisible activity at the scattering point, they represent a potential background source for all emulsion experiments hunting for decay topologies of short-lived particles like the lepton and charm mesons. extensive study of such hadronic kink signatures a dedicated experimental set-up has been built and exposed at the CERN PS hadron beam facility and it has collected about 300 000 pions with a fixed momentum ranging from 2 to 5 GeV/c. Each particle was tracked by silicon strip detectors to connect it to the proper track in the nuclear emulsion located in between. Threshold Cherenkov detectors for electron discrimination, a muon counter and an MWPC-based magnetic spectrometer completed the experimental configuration. A total of 222 white and 271 grey kinks could be successfully located in the emulsion target. Their angular and transverse momentum distributions were extensively studied.