Associated charm production in neutrino-nucleus interactions

In this paper a search for associated charm production both in neutral and charged current ?-nucleus interactions is presented. The improvement of automatic scanning systems in the CHORUS experiment allows an efficient search to be performed in emulsion for short-lived particles. Hence a search for rare processes, like the associated charm production, becomes possible through the observation of the double charm-decay topology with a very low background. About 130000 ? interactions located in the emulsion target have been analysed. Three events with two charm decays have been observed in the neutral-current sample with an estimated background of 0.18±0.05. The relative rate of the associated charm cross-section in deep inelastic ? interactions, ?(cc ?)/?NC DIS=(3.62+2.95 -2.42(stat)±0.54(syst))×10-3 has been measured. One event with two charm decays has been observed in charged-current ?µ interactions with an estimated background of 0.18±0.06 and the upper limit on associated charm production in charged-current interactions at 90% C.L. has been found to be ?(cc µ-)/?CC<9.69×10-4. © 2007 Springer-Verlag / Società Italiana di Fisica