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Register a new userMeasurement of the inclusive phi cross-section in pp collisions at sqrt(s) = 7 TeV
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The cross-section for inclusive phi meson production in pp collisions at a centre-of-mass energy of sqrt(s) = 7 TeV has been measured with the LHCb detector at the Large Hadron Collider. The differential cross-section is measured as a function of the phi transverse momentum p_T and rapidity y in the region 0.6 < p_T < 5.0 GeV/c and 2.44 < y < 4.06. The cross-section for inclusive phi production in this kinematic range is sigma(pp -> phi X) = 1758 pm 19(stat) ^{+43}_{-14}(syst) pm 182(scale) microbarn, where the first systematic uncertainty depends on the p_T and y region and the second is related to the overall scale. Predictions based on the Pythia 6.4 generator underestimate the cross-section.
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The production of B+- mesons in proton-proton collisions at sqrt(s)=7 TeV is studied using 35 pb-1 of data collected by the LHCb detector. The B+- mesons are reconstructed exclusively in the B+- -> J/psi K+- mode, with J/psi -> mu+ mu-. The differential production cross-section is measured as a function of the B+- transverse momentum in the fiducial region 0 < pT < 40 GeV/c and with rapidity 2.0 < y < 4.5. The total cross-section, summing up B+ and B-, is measured to be sigma(pp -> B+- X, 0 < pT < 40 GeV/c, 2.0 < y < 4.5) = 41.4 +- 1.5 (stat.) +- 3.1 (syst.) mub.
A measurement of the production cross-section for $Z$ bosons that decay to muons is presented. The data were recorded by the LHCb detector during $pp$ collisions at a centre-of-mass energy of 7 TeV, and correspond to an integrated luminosity of 1.0 fb$^{-1}$. The cross-section is measured for muons in the pseudorapidity range $2.0 < eta < 4.5$ with transverse momenta $p_{T} > 20$ GeV/c. The dimuon mass is restricted to $60 < M_{mu^{+}mu^{-}} < 120$ GeV/c$^{2}$. The measured cross-section is $$sigma_{Zrightarrowmu^{+}mu^{-}} = (76.0 pm 0.3 pm 0.5 pm 1.0 pm 1.3) , text{pb}$$ where the uncertainties are due to the sample size, systematic effects, the beam energy and the luminosity. This result is in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. The cross-section is also measured differentially as a function of kinematic variables of the $Z$ boson. Ratios of the production cross-sections of electroweak bosons are presented using updated LHCb measurements of $W$ boson production. A precise test of the Standard Model is provided by the measurement of the ratio $$frac{sigma_{W^{+}rightarrowmu^{+} u_{mu}} + sigma_{W^{-}rightarrowmu^{-}bar{ u}_{mu}}}{sigma_{Zrightarrowmu^{+}mu^{-}}} = 20.63pm0.09pm0.12pm0.05,$$ where the uncertainty due to luminosity cancels.
A measurement of the inclusive $W to mu u$ production cross-section using data from $pp$ collisions at a centre-of-mass energy of $sqrt{s} = 7 {rm , TeV}$ is presented. The analysis is based on an integrated luminosity of about $1.0 {rm , fb}^{-1}$ recorded with the LHCb detector. Results are reported for muons with a transverse momentum greater than $20 {rm , Gekern -0.1em V!/}c$ and pseudorapidity between 2.0 and 4.5. The $W^{+}$ and $W^{-}$ production cross-sections are measured to be $$sigma_{W^{+} to mu^{+} u} = 861.0 pm 2.0 pm 11.2 pm 14.7 {rm , pb},$$ $$sigma_{W^{-} to mu^{-}overline{ u}} = 675.8 pm 1.9 pm 8.8 pm 11.6 {rm , pb},$$ where the first uncertainty is statistical, the second is systematic and the third is due to the luminosity determination. Cross-section ratios and differential distributions as functions of the muon pseudorapidity are also presented. The ratio of $W^{+}$ to $W^{-}$ cross-sections in the same fiducial kinematic region is determined to be $$frac{sigma_{W^{+} to mu^{+} u}}{sigma_{W^{-} to mu^{-}overline{ u}}} = 1.274 pm 0.005 pm 0.009,$$ where the uncertainties are statistical and systematic, respectively. Results are in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics.
A study is presented of central exclusive production of $Upsilon(nS)$ states, where the $Upsilon(nS)$ resonances decay to the $mu^+mu^-$ final state, using $pp$ collision data recorded by the LHCb experiment. The cross-section is measured in the rapidity range $2<y(Upsilon)<4.5$ where the muons are reconstructed in the pseudorapidity range $2<eta(mu^pm)<4.5$. The data sample corresponds to an integrated luminosity of 2.9 fb$^{-1}$ and was collected at centre-of-mass energies of $7$ TeV and $8$ TeV. The measured $Upsilon(1S)$ and $Upsilon(2S)$ production cross-sections are begin{eqnarray} sigma(pp to pUpsilon(1S)p) &=& 9.0 pm 2.1 pm 1.7textrm{ pb and} onumber sigma(pp to pUpsilon(2S)p) &=& 1.3 pm 0.8 pm 0.3textrm{ pb}, onumber end{eqnarray} where the first uncertainties are statistical and the second are systematic. The $Upsilon(1S)$ cross-section is also measured as a function of rapidity and is found to be in good agreement with Standard Model predictions. An upper limit is set at 3.4 pb at the 95% confidence level for the exclusive $Upsilon(3S)$ production cross-section, including possible contamination from $chi_b(3P)toUpsilon(3S)gamma$ decays.
The production of $B^{pm}$ mesons is studied in $pp$ collisions at centre-of-mass energies of 7 and 13 TeV, using $B^{pm}rightarrow J/psi K^{pm}$ decays and data samples corresponding to 1.0 fb$^{-1}$ and 0.3 fb$^{-1}$, respectively. The production cross-sections summed over both charges and integrated over the transverse momentum range $0<p_{text{T}}< 40$ GeV/$c$ and the rapidity range $2.0<y<4.5$ are measured to be $sigma(pp rightarrow B^{pm} X, sqrt{s} = text{7 TeV}) = 43.0 pm 0.2 pm 2.5 pm 1.7mu b,$ $sigma(pp rightarrow B^{pm} X, sqrt{s} = text{13 TeV}) = 86.6 pm 0.5 pm 5.4 pm 3.4mu b,$ where the first uncertainties are statistical, the second are systematic, and the third are due to the limited knowledge of the $B^{pm}rightarrow J/psi K^{pm}$ branching fraction. The ratio of the cross-section at 13 TeV to that at 7 TeV is determined to be $2.02pm0.02text{(stat)}pm0.12text{(syst)}$. Differential cross-sections are also reported as functions of $p_{text{T}}$ and $y$. All results are in agreement with theoretical calculations based on the state-of-art fixed next-to-leading order quantum chromodynamics.
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