Charm fragmentation fractions and cc_ cross section in p–Pb collisions at √sNN = 5.02TeV

Abstract

The total charm-quark production cross section per unit of rapidity dσ(cc)/dy, and the fragmentation fractions of charm quarks to different charm-hadron species f (c → hc), are measured for the first time in p–Pb collisions at √ sNN = 5.02 TeV at midrapid ity (−0.96 < y < 0.04 in the centre-of-mass frame) using data collected by ALICE at the CERN LHC. The results are obtained based on all the available measure ments of prompt production of ground-state charm-hadron species: D0, D+, D+s , and J/ψ mesons, and +c and 0 c baryons. The resulting cross section is dσ(cc)/dy = 219.6 ± 6.3 (stat.) +10.5 −11.8 (syst.) +8.3 −2.9 (extr.) ± 5.4 (BR) ± 4.6 (lumi.)±19.5 (rapidity shape)+15.0 ( 0 c) mb, which is consistent with a binary scaling of pQCD calculations from pp collisions. The measured fragmentation fractions are compatible with those measured in pp collisions at √s = 5.02and 13 TeV, showing an increase in the relative production rates of charm baryons with respect to charm mesons in pp and p–Pb collisions compared with e+e− and e−p collisions. The pT-integrated nuclear modification factor of charm quarks, RpPb(cc) = 0.91 ± 0.04 (stat.)+0.08 −0.09 (syst.)+0.05 −0.03 (extr.) ± 0.03 (lumi.), is found to be consistent with unity and with theoretical predictions including nuclear modifications of the parton distribution functions.