Measurement of the D+/- production asymmetry in 7 TeV pp collisions

TL;DR

This paper measures the production asymmetry of D+/- mesons in 7 TeV proton-proton collisions at LHCb, finding a small asymmetry with no significant dependence on kinematic variables.

Contribution

It provides the first detailed measurement of D+/- production asymmetry in pp collisions at 7 TeV, using a large data sample and analyzing dependence on pseudorapidity and transverse momentum.

Findings

Measured asymmetry A_P = (-0.96 +/- 0.26 +/- 0.18)%

No significant dependence on ta or p_T observed

Results consistent with negligible direct CP violation

Abstract

The asymmetry in the production cross-section \sigma of D+/- mesons, A_P = (\sigma(D+) - \sigma(D-))/(\sigma(D+) + \sigma(D-)), is measured in bins of pseudorapidity \eta and transverse momentum p_T within the acceptance of the LHCb detector. The result is obtained with a sample of D+ -> K_S pi+ 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 < \eta < 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+ -> K_S pi+ decay is negligible. No significant dependence on \eta or p_T is observed.