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

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.

Measurement of the Ds+ - Ds- 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 phipi(+/-) decay mode in a data sample of 1.0/fb collected with the LHCb detector. The difference between pi+ and pi- 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.

Measurement of the $b$-quark production cross-section in 7 and 13 TeV $pp$ collisions

Measurements of the cross-section for producing bquark quarks in the reaction $ppto bbar{b} X$ are reported in 7 and 13 TeV collisions at the LHC as a function of the pseudorapidity $eta$ in the range $2<eta<5$ covered by the acceptance of the LHCb experiment. The measurements are done using semileptonic decays of $b$-flavored hadrons decaying into a ground-state charmed hadron in association with a muon. The cross-sections in the covered $eta$ range are $72.0pm 0.3pm6.8~mu$b and $144pm 1pm 21~mu$b for 7 and 13 TeV. The ratio is $2.00pm0.02pm0.26$, where the quoted uncertainties are statistical and systematic, respectively. The agreement with theoretical expectation is good at 7 TeV, but differs somewhat at 13 TeV. The measured ratio of cross-sections is larger at lower $eta$ than the model prediction.

Measurement of $D_s^{pm}$ production asymmetry in $pp$ collisions at $sqrt{s} =7$ and 8 TeV

The inclusive $D_s^{pm}$ production asymmetry is measured in $pp$ collisions collected by the LHCb experiment at centre-of-mass energies of $sqrt{s} =7$ and 8 TeV. Promptly produced $D_s^{pm}$ mesons are used, which decay as $D_s^{pm}tophipi^{pm}$, with $phito K^+K^-$. The measurement is performed in bins of transverse momentum, $p_{rm T}$, and rapidity, $y$, covering the range $2.5<p_{rm T}<25.0$ GeV$/c$ and $2.0<y<4.5$. No kinematic dependence is observed. Evidence of nonzero $D_s^{pm}$ production asymmetry is found with a significance of 3.3 standard deviations.

Measurement of psi(2S) meson production in pp collisions at sqrt(s)=7 TeV

The differential cross-section for the inclusive production of psi(2S) mesons in pp collisions at sqrt(s)=7 TeV has been measured with the LHCb detector. The data sample corresponds to an integrated luminosity of 36 pb-1. The psi(2S) mesons are reconstructed in the decay channels psi(2S) -> mu+ mu- and psi(2S) -> J/psi pi+ pi-, with the J/psi meson decaying into two muons. Results are presented both for promptly produced psi(2S) mesons and for those originating from b-hadron decays. In the kinematic range pT(psi(2S)) <= 16 GeV/c and 2 < y(psi(2S)) <= 4.5 we measure 1.44 +- 0.01 +- 0.12+0.2-0.4 mub for prompt psi(2S) production and 0.25 +- 0.01 +- 0.02 mub for psi(2S) from b-hadron decays, where the last uncertainty on the prompt cross-section is due to the unknown psi(2S) polarization. Recent QCD calculations are found to be in good agreement with our measurements. Combining the present result with the LHCb J/psi measurements we determine the inclusive branching fraction B(b -> psi(2S) X) = (2.73 +- 0.06 +- 0.16 +- 0.24) x 10^(-3), where the last uncertainty is due to the B(b -> J/psi X), B(J/psi -> mu+ mu-) and B(psi(2S) -> e+ e-) branching fraction uncertainties. All above results are corrected by an erratum included as an appendix.