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Register a new userMeasurement of the cross-section for Z->e+e- production in pp collisions at sqrt{s}=7TeV
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A measurement of the cross-section for pp->Z->e+e- is presented using data at sqrt{s}=7TeV corresponding to an integrated luminosity of 0.94 fb^{-1}. The process is measured within the kinematic acceptance pT>20GeV/c and 2<eta<4.5 for the daughter electrons and dielectron invariant mass in the range 60--120GeV/c^2. The cross-section is determined to be sigma(pp->Z->e+e-)=76.0+-0.8+-2.0+-2.6pb where the first uncertainty is statistical, the second is systematic and the third is the uncertainty in the luminosity. The measurement is performed as a function of Z rapidity and as a function of an angular variable which is closely related to the Z transverse momentum. The results are compared with previous LHCb measurements and with theoretical predictions from QCD.
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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 production cross-section of Z bosons in pp collisions at $sqrt{s} = 13$ TeV is presented using dimuon and dielectron final states in LHCb data. The cross-section is measured for leptons with pseudorapidities in the range $2.0 < eta < 4.5$, transverse momenta $p_text{T} > 20$ GeV and dilepton invariant mass in the range $60<m(ellell)<120$ GeV. The integrated cross-section from averaging the two final states is begin{equation*}sigma_{text{Z}}^{ellell} = 194.3 pm 0.9 pm 3.3 pm 7.6text{ pb,}end{equation*} where the first uncertainty is statistical, the second is due to systematic effects, and the third is due to the luminosity determination. In addition, differential cross-sections are measured as functions of the Z boson rapidity, transverse momentum and the angular variable $phi^*_eta$.
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.
Using a data sample corresponding to an integrated luminosity of $2.0,fb^{-1}$, collected by the LHCb experiment, the production of the $eta_c(1S)$ state in proton-proton collisions at a centre-of-mass energy of $sqrt{s}=13 text{ TeV}$ is studied in the rapidity range ${2.0 < y < 4.5}$ and in the transverse momentum range ${6.5 < p_{T} < 14.0text{ GeV}}$. The cross-section for prompt production of $eta_c(1S)$ mesons relative to that of the $J/psi$ meson is measured using the ${pbar{p}}$ decay mode and is found to be ${sigma_{eta_c(1S)}/sigma_{J/psi} = 1.69 pm 0.15 pm 0.10 pm 0.18}$. The quoted uncertainties are, in order, statistical, systematic and due to uncertainties on the branching fractions of the ${J/psito p bar{p}}$ and ${eta_cto p bar{p}}$ decays. The prompt $eta_c(1S)$ production cross-section is determined to be ${sigma_{eta_c(1S)} = 1.26 pm 0.11pm 0.08 pm 0.14 ,mu b}$, where the last uncertainty includes that on the ${J/psi}$ meson cross-section. The ratio of the branching fractions of $b$-hadron decays to the $eta_c(1S)$ and ${J/psi}$ states is measured to be ${mathcal{B}_{btoeta_c X}/mathcal{B}_{bto J/psi X} = 0.48 pm 0.03 pm 0.03 pm 0.05}$, where the last uncertainty is due to those on the branching fractions of the ${J/psi to p bar{p}}$ and ${eta_cto p bar{p}}$ decays. The difference between the ${J/psi}$ and $eta_c(1S)$ masses is also determined to be ${113.0 pm 0.7 pm 0.1text{ MeV}}$, which is the most precise single measurement of this quantity to date.
A measurement of the cross-section for $W to e u$ production in $pp$ collisions is presented using data corresponding to an integrated luminosity of $2,$fb$^{-1}$ collected by the LHCb experiment at a centre-of-mass energy of $sqrt{s}=8,$TeV. The electrons are required to have more than $20,$GeV of transverse momentum and to lie between 2.00 and 4.25 in pseudorapidity. The inclusive $W$ production cross-sections, where the $W$ decays to $e u$, are measured to be begin{equation*} sigma_{W^{+} to e^{+} u_{e}}=1124.4pm 2.1pm 21.5pm 11.2pm 13.0,mathrm{pb}, end{equation*} begin{equation*} sigma_{W^{-} to e^{-}bar{ u}_{e}}=,,,809.0pm 1.9pm 18.1pm,,,7.0pm phantom{0}9.4,mathrm{pb}, end{equation*} where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. Differential cross-sections as a function of the electron pseudorapidity are measured. The $W^{+}/W^{-}$ cross-section ratio and production charge asymmetry are also reported. Results are compared with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. Finally, in a precise test of lepton universality, the ratio of $W$ boson branching fractions is determined to be begin{equation*} mathcal{B}(W to e u)/mathcal{B}(W to mu u)=1.020pm 0.002pm 0.019, end{equation*} where the first uncertainty is statistical and the second is systematic.
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