Measurement of charm production in neutrino charged-current interactions

The nuclear emulsion target of the CHORUS detector was exposed to the wide-band neutrino beam of the CERN SPS of 27 GeV average neutrino energy from 1994 to 1997. In total about 100000 charged-current neutrino interactions with at least one identified muon were located in the emulsion target and fully reconstructed, using newly developed automated scanning systems. Charmed particles were searched for by a program recognizing particle decays. The observation of the decay in nuclear emulsion makes it possible to select a sample with very low background and minimal kinematical bias. 2013 charged-current interactions with a charmed hadron candidate in the final state were selected and confirmed through visual inspection. The charm production rate induced by neutrinos relative to the charged-current cross-section is measured to be $\sigma(\nu_{\mu}N \to \mu^{-}CX/\sigma(CC)=(5.75\pm032(stat)\pm0.30(syst))%$. The charm production cross-section as a function of the neutrino energy is also obtained. The results are in good agreement with previous measurements. The charm-quark hadronization produces the following charmed hadrons with relative fractions (in %): $f_{D^{0}}= 43.7\pm 4.5,f_{\lambda^{+}_{c}}=19.2\pm 4.2,f_{D^{+}}= 25.3\pm 4.2$, and $f_{D^{+}_{s}}=11.8\pm4.7$.