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Register a new userMeasurement of forward top pair production in the dilepton channel in $pp$ collisions at $sqrt{s}=13$ TeV
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Forward top quark pair production is studied in $pp$ collisions in the $mu eb$ final state using a data sample corresponding to an integrated luminosity of 1.93 fb$^{-1}$ collected with the LHCb experiment at a centre-of-mass energy of 13 TeV. The cross-section is measured in a fiducial region where both leptons have a transverse momentum greater than 20 GeV and a pseudorapidity between 2.0 and 4.5. The quadrature sum of the azimuthal separation and the difference in pseudorapidities, denoted $Delta R$, between the two leptons must be larger than 0.1. The $b$-jet axis is required to be separated from both leptons by a $Delta R$ of 0.5, and to have a transverse momentum in excess of 20 GeV and a pseudorapidity between 2.2 and 4.2. The cross-section is measured to be $$sigma_{tbar{t}}= 126pm19,(mathrm{stat})pm16,(mathrm{syst})pm5,(mathrm{lumi}),,mathrm{ fb}$$ where the first uncertainty is statistical, the second is systematic, and the third is due to the luminosity determination. The measurement is compatible with the Standard Model prediction.
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The production cross-sections of $Upsilon(1S)$, $Upsilon(2S)$ and $Upsilon(3S)$ mesons in proton-proton collisions at $sqrt{s}$= 13 TeV are measured with a data sample corresponding to an integrated luminosity of $277 pm 11$ $rm pb^{-1}$ recorded by the LHCb experiment in 2015. The $Upsilon$ mesons are reconstructed in the decay mode $Upsilontomu^{+}mu^{-}$. The differential production cross-sections times the dimuon branching fractions are measured as a function of the $Upsilon$ transverse momentum, $p_{rm T}$, and rapidity, $y$, over the range $0 < p_{rm T}< 30$ GeV/c and $2.0 < y < 4.5$. The ratios of the cross-sections with respect to the LHCb measurement at $sqrt{s}$= 8 TeV are also determined. The measurements are compared with theoretical predictions based on NRQCD.
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 cross-section of $J/psi$ pairs is measured using a data sample of $pp$ collisions collected by the LHCb experiment at a centre-of-mass energy of $sqrt{s} = 13 ,{mathrm{TeV}}$, corresponding to an integrated luminosity of $279 pm 11 ,{mathrm{pb^{-1}}}$. The measurement is performed for $J/psi$ mesons with a transverse momentum of less than $10 ,{mathrm{GeV}}/c$ in the rapidity range $2.0<y<4.5$. The production cross-section is measured to be $15.2 pm 1.0 pm 0.9 ,{mathrm{nb}}$. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the $J/psi$ pair are measured and compared to theoretical predictions.
The production of $mathit{Xi}_{cc}^{++}$ baryons in proton-proton collisions at a centre-of-mass energy of $sqrt{s}=13$ TeV is measured in the transverse-momentum range $4<p_mathrm{T}<15~mathrm{GeV}$/$c$ and the rapidity range $2.0<y<4.5$. The data used in this measurement correspond to an integrated luminosity of 1.7 $mathrm{fb}^{-1}$, recorded by the LHCb experiment during 2016. The ratio of the $mathit{Xi}_{cc}^{++}$ production cross-section times the branching fraction of the $mathit{Xi_{cc}^{++} to Lambda_{c}^{+} K^- pi^+ pi^+}$ decay relative to the prompt $mathit{Lambda_c^{+}}$ production cross-section is found to be $(2.22pm 0.27 pm 0.29)times 10^{-4}$, assuming the central value of the measured $mathit{Xi_{cc}^{++}}$ lifetime, where the first uncertainty is statistical and the second systematic.
Measurements of normalized differential cross-sections of top quark pair ($tbar t$) production are presented as a function of the mass, the transverse momentum and the rapidity of the $tbar t$ system in proton-proton collisions at center-of-mass energies of $sqrt{s}$ = 7 TeV and 8 TeV. The dataset corresponds to an integrated luminosity of 4.6 fb$^{-1}$ at 7 TeV and 20.2 fb$^{-1}$ at 8 TeV, recorded with the ATLAS detector at the Large Hadron Collider. Events with top quark pair signatures are selected in the dilepton final state, requiring exactly two charged leptons and at least two jets with at least one of the jets identified as likely to contain a $b$-hadron. The measured distributions are corrected for detector effects and selection efficiency to cross-sections at the parton level. The differential cross-sections are compared with different Monte Carlo generators and theoretical calculations of $tbar t$ production. The results are consistent with the majority of predictions in a wide kinematic range.
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