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Register a new userMeasurement of differential $bbar{b}$- and $cbar{c}$-dijet cross-sections in the forward region of $pp$ collisions at $sqrt{s}=13 ~ mathrm{TeV}$
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The inclusive $b bar{b}$- and $c bar{c}$-dijet production cross-sections in the forward region of $pp$ collisions are measured using a data sample collected with the LHCb detector at a centre-of-mass energy of 13 TeV in 2016. The data sample corresponds to an integrated luminosity of 1.6 fb$^{-1}$. Differential cross-sections are measured as a function of the transverse momentum and of the pseudorapidity of the leading jet, of the rapidity difference between the jets, and of the dijet invariant mass. A fiducial region for the measurement is defined by requiring that the two jets originating from the two $b$ or $c$ quarks are emitted with transverse momentum greater than 20 GeV$/c$, pseudorapidity in the range $2.2 < eta < 4.2$, and with a difference in the azimuthal angle between the two jets greater than 1.5. The integrated $b bar{b}$-dijet cross-section is measured to be $53.0 pm 9.7$ nb, and the total $c bar{c}$-dijet cross-section is measured to be $73 pm 16$ nb. The ratio between $c bar{c}$- and $b bar{b}$-dijet cross-sections is also measured and found to be $1.37 pm 0.27$. The results are in agreement with theoretical predictions at next-to-leading order.
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Production cross-sections of prompt charm mesons are measured with the first data from $pp$ collisions at the LHC at a centre-of-mass energy of $13,mathrm{TeV}$. The data sample corresponds to an integrated luminosity of $4.98 pm 0.19,mathrm{pb}^{-1}$ collected by the LHCb experiment. The production cross-sections of $D^{0}$, $D^{+}$, $D_{s}^{+}$, and $D^{*+}$ mesons are measured in bins of charm meson transverse momentum, $p_{mathrm{T}}$, and rapidity, $y$, and cover the range $0 < p_{mathrm{T}} < 15,mathrm{GeV}/c$ and $2.0 < y < 4.5$. The inclusive cross-sections for the four mesons, including charge conjugation, within the range of $1 < p_{mathrm{T}} < 8,mathrm{GeV}/c$ are found to be begin{equation} sigma(pp to D^{0} X) = 2072 pm 2 pm 124,mumathrm{b} sigma(pp to D^{+} X) = 834 pm 2 pm phantom{1}78,mumathrm{b} sigma(pp to D_{s}^{+} X) = 353 pm 9 pm phantom{1}76,mumathrm{b} sigma(pp to D^{*+} X) = 784 pm 4 pm phantom{1}87,mumathrm{b} end{equation} where the uncertainties are due to statistical and systematic uncertainties, respectively.
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 $B^{pm}$ 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.
The associated production of a Z boson or an off-shell photon $gamma^*$ with a bottom quark in the forward region is studied using proton-proton collisions at a centre-of-mass energy of $7{mathrm{,Tekern -0.1em V}}$. The Z bosons are reconstructed in the ${text{Z}/gamma^*}!rightarrow{mu^{+}mu^{-}}$ final state from muons with a transverse momentum larger than $20{mathrm{,Gekern -0.1em V}}$, while two transverse momentum thresholds are considered for jets ($10{mathrm{,Gekern -0.1em V}}$ and $20{mathrm{,Gekern -0.1em V}}$). Both muons and jets are reconstructed in the pseudorapidity range $2.0 < eta < 4.5$. The results are based on data corresponding to $1.0{,mbox{fb}^{-1}}$ recorded in 2011 with the LHCb detector. The measurement of the Z+b-jet cross-section is normalized to the Z+jet cross-section. The measured cross-sections are begin{equation*} sigma(text{$text{Z}/gamma^*(mu^{+}mu^{-})$+b-jet}) = 295 pm 60~(text{stat}) pm 51~(text{syst}) pm 10~(text{lumi}) {,mbox{fb}} end{equation*} for ${p_{rm T}}$(jet)$>10{mathrm{,Gekern -0.1em V}}$, and begin{equation*} sigma(text{$text{Z}/gamma^*(mu^{+}mu^{-})$+b-jet}) = 128 pm 36~(text{stat}) pm 22~(text{syst}) pm 5~(text{lumi}) {,mbox{fb}} end{equation*} for ${p_{rm T}}$(jet)$>20{mathrm{,Gekern -0.1em V}}$.
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