Associated charm production in neutrino–nucleus interactions.

In this paper a search for associated charm production both in neutral and charged current ν-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 ν 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 ν interactions, σ(cc̄ν)/σ_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 ν_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 σ(cc̄μ^-)/σ_CC<9.69×10^-4. [ABSTRACT FROM AUTHOR]