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

Heavy quark production in 7 TeV centre-of-mass energy pp collisions at the LHC is not necessarily flavour symmetric. The production asymmetry, A _P, between Ds+ and Ds- mesons is studied using the φπ ^± decay mode in a data sample of 1.0fb ^-1 collected with the LHCb detector. The difference between π ⁺ and π ^- detection efficiencies is determined using the ratios of fully reconstructed to partially reconstructed D ^± decays. The overall production asymmetry in the Ds± rapidity region 2.0 to 4.5 with transverse momentum larger than 2 GeV is measured to be A _P=(-0.33±0.22±0.10)%. This result can constrain models of heavy flavour production.