Measurement of the D± production asymmetry in 7 TeV pp collisions

The asymmetry in the production cross-section σ of D± mesons, Ap = [σ(D+)− σ(D−)] / [σ(D+)+ σ(D−)] (for equation formatting, see published paper) is measured in bins of pseudorapidity η and transverse momentum pT within the acceptance of the LHCb detector. The result is obtained with a sample of D+ → K0 Sπ+ decays corresponding to an integrated luminosity of 1.0 fb−1, collected in pp collisions at a centre of mass energy of 7 TeV at the Large Hadron Collider. When integrated over the kinematic range 2.0 < pT < 18.0 GeV/c and 2.20 < η < 4.75, the production asymmetry is AP = (−0.96 ± 0.26 ± 0.18)%. The uncertainties quoted are statistical and systematic, respectively. The result assumes that any direct CP violation in the D+ → K0 Sπ+ decay is negligible. No significant dependence on η or pT is observed.