Measurement of D*+- production and the charm contribution to F_2 in deep inelastic scattering at HERA

TL;DR

This paper measures D* meson production in deep inelastic scattering at HERA to determine the charm contribution to the proton structure function, finding it increases with Q^2 from about 10% to 30%.

Contribution

It provides the first detailed measurement of D* production cross sections and the charm contribution to F_2 in a broad kinematic range at HERA.

Findings

Differential cross sections agree with NLO QCD calculations.

Charm contribution to F_2 increases with Q^2.

F^ccbar_2/F_2 ratio rises from 10% to 30%.

Abstract

The production of D*+-(2010) mesons in deep inelastic scattering has been measured in the ZEUS detector at HERA using an integrated luminosity of 37 pb^-1. The decay channels D*+ -> D0 pi+(+c.c.), with D0 -> K- pi+ or D0 ->K- pi- pi+ pi+, have been used to identify the D mesons. The e+p cross section for inclusive D*+- production with 1<Q^2<600 GeV^2 and 0.02<y<0.7 is 8.31 +- 0.31(stat.) +0.30-0.50(syst.) nb in the kinematic region 1.5< pT(D*+-)<15 GeV and |eta(D*+-)|<1.5. Differential cross sections are consistent with a next-to-leading-order perturbative-QCD calculation when using charm-fragmentation models which take into account the interaction of the charm quark with the proton remnant. The observed cross section is extrapolated to the full kinematic region in pT(D*+-) and eta(D*+-) in order to determine the charm contribution, F^ccbar_2(x,Q^2), to the proton structure function. The ratio F^ccbar_2/F_2 rises from ~10% at Q^2 ~1.8 GeV^2 to ~30% at Q^2 ~130 GeV^2 for x values in the range 10^-4 to 10-3.