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Register a new userMeasurement of B meson production cross-sections in proton-proton collisions at sqrt(s)= 7 TeV
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The production cross-sections of B mesons are measured in pp collisions at a centre-of-mass energy of 7 TeV, using data collected with the LHCb detector corresponding to a integrated luminosity of 0.36 fb-1. The B+, B0 and Bs0 mesons are reconstructed in the exclusive decays B+ -> J/psi K+, B0 -> J/psi K*0 and Bs0 -> J/psi phi, with J/psi -> mu+ mu-, K*0 -> K+ pi- and phi -> K+ K-. The differential cross-sections are measured as functions of B meson transverse momentum pT and rapidity y, in the range 0 < pT < 40 GeV/c and 2.0 < y < 4.5. The integrated cross-sections in the same pT and y ranges, including charge-conjugate states, are measured to be sigma(pp -> B+ + X) = 38.9 +- 0.3 (stat.) +- 2.5 (syst.) +- 1.3 (norm.) mub, sigma(pp -> B0 + X) = 38.1 +- 0.6 (stat.) +- 3.7 (syst.) +- 4.7 (norm.) mub, sigma(pp -> Bs0 + X) = 10.5 +- 0.2 (stat.) +- 0.8 (syst.) +- 1.0 (norm.) mub, where the third uncertainty arises from the pre-existing branching fraction measurements.
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The cross-sections of $psi(2S)$ meson production in proton-proton collisions at $sqrt{s}=13~mathrm{TeV}$ are measured with a data sample collected by the LHCb detector corresponding to an integrated luminosity of $275~pmathrm{b}^{-1}$. The production cross-sections for prompt $psi(2S)$ mesons and those for $psi(2S)$ mesons from $b$-hadron decays ($psi{(2S)}mathrm{-from-}b$) are determined as functions of the transverse momentum, $p_{mathrm{T}}$, and the rapidity, $y$, of the $psi(2S)$ meson in the kinematic range $2<p_{mathrm{T}}<20~mathrm{GeV}/c$ and $2.0<y<4.5$. The production cross-sections integrated over this kinematic region are begin{equation*} begin{split} sigma(mbox{prompt }psi(2S),13~mathrm{TeV}) &= {1.430 pm 0.005(mathrm{stat}) pm 0.099 (mathrm{syst})mumathrm{b}}, sigma(psi(2S)mathrm{-from-}b,13~mathrm{TeV})&={0.426 pm 0.002(mathrm{stat}) pm0.030 (mathrm{syst})mumathrm{b}}. end{split} end{equation*} A new measurement of $psi(2S)$ production cross-sections in $pp$ collisions at $sqrt{s}=7~mathrm{TeV}$ is also performed using data collected in 2011, corresponding to an integrated luminosity of $614~{pmathrm{b}^{-1}}$.The integrated production cross-sections in the kinematic range $3.5<p_{mathrm{T}}<14~mathrm{GeV}/c$ and $2.0<y<4.5$ are begin{equation*} begin{split} sigma(mbox{prompt }psi(2S),7~mathrm{TeV}) &={0.471 pm0.001 (mathrm{stat}) pm 0.025 (mathrm{syst})mumathrm{b}}, sigma(psi(2S)mathrm{-from-}b,7~mathrm{TeV}) &={0.126pm0.001 (mathrm{stat}) pm0.008 (mathrm{syst})mumathrm{b}}. end{split} end{equation*} All results show reasonable agreement with theoretical calculations.
The measurement of the heavy-flavour production cross sections in pp collisions at the LHC will allow to test perturbative QCD calculations in a new energy domain. Moreover, within the physics program of the ALICE experiment, it will provide the reference for the study of medium effects in Pb-Pb collisions, where heavy quarks are regarded as sensitive probes of parton-medium interaction dynamics. We present the status and first preliminary results of charm and beauty production measurements with the ALICE experiment, using hadronic D meson decays and semi-leptonic D and B meson decays, including the first cross section measurement of muons from heavy flavour decays at forward rapidity. We also describe the preliminary cross section measurement for J/psi production, obtained using the di-electron decay channel at central rapidity and the di-muon decay channel at forward rapidity.
Production of $B_c^+$ mesons in proton-proton collisions at a center-of-mass energy of 8 TeV is studied with data corresponding to an integrated luminosity of $2.0~{rm fb}^{-1}$ recorded by the LHCb experiment. The ratio of production cross-sections times branching fractions between the $B_c^+to J/psi pi^+$ and $B^+to J/psi K^+$ decays is measured as a function of transverse momentum and rapidity in the regions $0 < p_{rm T} < 20~{rm GeV}/c$ and $2.0 < y < 4.5$. The ratio in this kinematic range is measured to be $(0.683pm0.018pm0.009)%$, where the first uncertainty is statistical and the second systematic.
A measurement of $Zrightarrowtau^+tau^-$ production cross-section is presented using data, corresponding to an integrated luminosity of 2 fb$^{-1}$, from $pp$ collisions at $sqrt{s}=8$ TeV collected by the LHCb experiment. The $tau^+tau^-$ candidates are reconstructed in final states with the first tau lepton decaying leptonically, and the second decaying either leptonically or to one or three charged hadrons. The production cross-section is measured for $Z$ bosons with invariant mass between 60 and 120 GeV/$c^2$, which decay to tau leptons with transverse momenta greater than 20 GeV/$c$ and pseudorapidities between 2.0 and 4.5. The cross-section is determined to be $sigma_{pprightarrow{}Zrightarrow{}tau^+tau^-} = 95.8 pm 2.1 pm 4.6 pm 0.2 pm 1.1 mathrm{pb}$, where the first uncertainty is statistical, the second is systematic, the third is due to the LHC beam energy uncertainty, and the fourth to the integrated luminosity uncertainty. This result is compatible with NNLO Standard model predictions. The ratio of the cross-sections for $Zrightarrowtau^+tau^-$ to $Zrightarrowmu^+mu^-$ ($Zrightarrow{}e^+e^-$), determined to be $1.01 pm 0.05$ ($1.02 pm 0.06$), is consistent with the lepton-universality hypothesis in $Z$ decays.
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.
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