Charm-quark fragmentation fractions and production cross section at mid rapidity in pp collisions at the LHC

Recent p(T)-integrated cross-section measurements of the ground-state charm mesons and baryons, D-0, D+, D-s(+), Lambda(+)(c), and Xi(0)(c) are used to evaluate the charm fragmentation fractions and production cross section per unit of rapidity at midrapidity (vertical bar y vertical bar < 0.5), in pp collisions at root s = 5.02 TeV at the LHC. The latter is d sigma(c<(c)over) (bar>)/dy vertical bar(vertical bar y vertical bar<0.5) = 1165 +/- 44(stat)(-101)(+131) (syst) mu b. These measurements were obtained for the first time in hadronic collisions at the LHC, including the charm baryon states, recently measured by ALICE at midrapidity. The charm fragmentation fractions differ significantly from the values measured in e(+)e(-) and ep collisions, providing evidence of the dependence of the parton-to-hadron fragmentation fractions on the collision system, indicating that the assumption of their universality is not supported by the measured cross sections. An increase of a factor of about 3.3 for the fragmentation fraction for the Lambda(+)(c) with a significance of 5 sigma between the values obtained in pp collisions and those obtained in e(+)e(-) (ep) collisions is reported. The fragmentation fraction for the Xi(0)(c) was obtained for the first time in any collision system. The measured fragmentation fractions were used to update the c (c) over bar cross sections per unit of rapidity at vertical bar y vertical bar < 0.5 at root s = 2.76 and 7 TeV, which are about 40% higher than the previously published results. The data were compared with perturbative-QCD calculations and lie at the upper edge of the theoretical bands.

Automated summary

This study measured the fragmentation fractions and production cross sections of charm mesons and baryons in p p collisions at the LHC. The results show that the fragmentation fractions are dependent on the collision system and differ from previous measurements in e(+)e(-) and ep collisions. An increase in the fragmentation fraction of Λ(c) was observed. The measured fragmentation fractions are higher than previous results and lie at the upper edge of theoretical calculations.