Measurement of the D± Production Asymmetry in 7 TeV pp Collisions

The asymmetry in the production cross-section σ of D± mesons, A_P = {σ(D+) − σ(D−)}/{σ(D+) + σ(D−)},is measured in bins of pseudorapidity η and transverse momentum p_T within the acceptance of the LHCb detector. The result is obtained with a sample of D+ → K0S π+ 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 < p_T < 18.0 GeV/c and 2.20 < η < 4.75, the production asymmetry is A_P = (−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+ → K0S π+ decay is negligible. No significant dependence on η or p_T is observed.