A precision measurement of the $Z$ boson production cross-section at $\sqrt{s} = 13$ TeV in the forward region is presented, using $pp$ collision data collected by the LHCb detector, corresponding to an integrated luminosity of 5.1 fb$^{-1}$. The production cross-section is measured using $Z\rightarrow\mu^+\mu^-$ events within the fiducial region defined as pseudorapidity $2.0<\eta<4.5$ and transverse momentum $p_{T}>20$ GeV/$c$ for both muons and dimuon invariant mass $60<M_{\mu\mu}<120$ GeV/$c^2$. The integrated cross-section is determined to be $\sigma (Z \rightarrow \mu^+ \mu^-)$ = 196.4 $\pm$ 0.2 $\pm$ 1.6 $\pm$ 3.9~pb, where the first uncertainty is statistical, the second is systematic, and the third is due to the luminosity determination. The measured results are in agreement with theoretical predictions within uncertainties.
Relative uncertainty for the integrated $Z -> \mu^{+} \mu^{-}$ cross-section measurement. The total uncertainty is the quadratic sum of uncertainties from statistical, systematic and luminosity contributions.
Final state radiation correction used in the $y^{Z}$ cross-section measurement. The first uncertainty is statistical and the second is systematic.
Final state radiation correction used in the $p_{T}^{Z}$ cross-section measurement. The first uncertainty is statistical and the second is systematic.
The production of $\Upsilon (nS)$ mesons ($n=1,2,3$) in $p$Pb and Pb$p$ collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{NN}}=8.16$ TeV is measured by the LHCb experiment, using a data sample corresponding to an integrated luminosity of 31.8 nb$^{-1}$. The $\Upsilon (nS)$ mesons are reconstructed through their decays into two opposite-sign muons. The measurements comprise the differential production cross-sections of the $\Upsilon (1S)$ and $\Upsilon (2S)$ states, their forward-to-backward ratios and nuclear modification factors, performed as a function of the transverse momentum $p_{\mathrm{T}}$ and rapidity in the nucleon-nucleon centre-of-mass frame $y^*$ of the $\Upsilon (nS)$ states, in the kinematic range $p_{\rm{T}}<25$ GeV/$c$ and $1.5<y^*<4.0$ ($-5.0<y^*<-2.5$) for $p$Pb (Pb$p$) collisions. In addition, production cross-sections for $\Upsilon (3S)$ are measured integrated over phase space and the production ratios between all three $\Upsilon (nS)$ states are determined. The measurements are compared to theoretical predictions and suppressions for quarkonium in $p$Pb collisions are observed.
$\Upsilon(1S)$ production cross-section in $p$Pb, as a function of $p_{T}$ and $y*$. The uncertainty is the sum in quadrature of the statistical and systematic components.
$\Upsilon(1S)$ production cross-section in Pb$p$, as a function of $p_{T}$ and $y^*$. The uncertainty is the sum in quadrature of the statistical and systematic components.
$\Upsilon(1S)$ production cross-section in $p$Pb and Pb$p$, as a function of $p_{T}$. The uncertainty is the sum in quadrature of the statistical and systematic components.
The cross-section for inelastic proton-proton collisions at a centre-of-mass energy of 13\,TeV is measured with the LHCb detector. The fiducial cross-section for inelastic interactions producing at least one prompt long-lived charged particle with momentum $p>2$\,GeV/$c$ in the pseudorapidity range $2<\eta<5$ is determined to be $\sigma_{\rm acc}= 62.2 \pm 0.2 \pm 2.5$\,mb. The first uncertainty is the intrinsic systematic uncertainty of the measurement, the second is due to the uncertainty on the integrated luminosity. The statistical uncertainty is negligible. Extrapolation to full phase space yields the total inelastic proton-proton cross-section $\sigma_{\rm inel}= 75.4 \pm 3.0 \pm 4.5$\,mb, where the first uncertainty is experimental and the second due to the extrapolation. An updated value of the inelastic cross-section at a centre-of-mass energy of 7\,TeV is also reported.
The cross-section for inelastic $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 13$ TeV, yielding one or more prompt long-lived charged particles in the kinematic range $p > 2.0$ GeV/$c$ and $2.0 < \eta < 5.0$ (LHCb acceptance). The quoted uncertainty that is almost completely systematic in nature as the purely statistical uncertainty is found negligible. A particle is long-lived if its proper (mean) lifetime is larger than 30 ps, and it is prompt if it is produced directly in the $pp$ interaction or if none of its ancestors is long-lived.
The total cross-section for inelastic $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 13$ TeV, extrapolated from Monte Carlo in similar way to measurement at $\sqrt{s}=7$ TeV.
Update of the total cross-section for inelastic $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 7$ TeV due to improved calibration of the luminosity scale.
Measurements are presented of electroweak boson production using data from $pp$ collisions at a centre-of-mass energy of $\sqrt{s} = 8\mathrm{\,Te\kern -0.1em V}$. The analysis is based on an integrated luminosity of $2.0\mathrm{\,fb}^{-1}$ recorded with the LHCb detector. The bosons are identified in the $W\rightarrow\mu\nu$ and $Z\rightarrow\mu^{+}\mu^{-}$ decay channels. The cross-sections are measured for muons in the pseudorapidity range $2.0 < \eta < 4.5$, with transverse momenta $p_{\rm T} > 20{\mathrm{\,Ge\kern -0.1em V\!/}c}$ and, in the case of the $Z$ boson, a dimuon mass within $60 < M_{\mu^{+}\mu^{-}} < 120{\mathrm{\,Ge\kern -0.1em V\!/}c^{2}}$. The results are \begin{align*} \sigma_{W^{+}\rightarrow\mu^{+}\nu} &= 1093.6 \pm 2.1 \pm 7.2 \pm 10.9 \pm 12.7{\rm \,pb} \, , \sigma_{W^{-}\rightarrow\mu^{-}\bar{\nu}} &= \phantom{0}818.4 \pm 1.9 \pm 5.0 \pm \phantom{0}7.0 \pm \phantom{0}9.5{\rm \,pb} \, , \sigma_{Z\rightarrow\mu^{+}\mu^{-}} &= \phantom{00}95.0 \pm 0.3 \pm 0.7 \pm \phantom{0}1.1 \pm \phantom{0}1.1{\rm \,pb} \, , \end{align*} 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. The evolution of the $W$ and $Z$ boson cross-sections with centre-of-mass energy is studied using previously reported measurements with $1.0\mathrm{\,fb}^{-1}$ of data at $7\mathrm{\,Te\kern -0.1em V}$. Differential distributions are also presented. Results are in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics.
Inclusive cross-section for $W^+$ and $W^-$ boson production in bins of muon pseudorapidity. The uncertainties are statistical, systematic, beam and luminosity.
Inclusive cross-section for $Z$ boson production in bins of rapidity. The uncertainties are statistical, systematic, beam and luminosity.
Inclusive cross-section for $Z$ boson production in bins of transverse momentum. The uncertainties are statistical, systematic, beam and luminosity.
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 $$\sigma_{Z\rightarrow\mu^{+}\mu^{-}} = (76.0 \pm 0.3 \pm 0.5 \pm 1.0 \pm 1.3) \, \text{pb}$$ 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 $$\frac{\sigma_{W^{+}\rightarrow\mu^{+}\nu_{\mu}} + \sigma_{W^{-}\rightarrow\mu^{-}\bar{\nu}_{\mu}}}{\sigma_{Z\rightarrow\mu^{+}\mu^{-}}} = 20.63\pm0.09\pm0.12\pm0.05,$$ where the uncertainty due to luminosity cancels.
Inclusive cross-section for $Z$ boson production in bins of rapidity. The uncertainties are statistical, systematic, beam and luminosity.
Inclusive cross-section for $Z$ boson production in bins of transverse momentum. The uncertainties are statistical, systematic, beam and luminosity.
Inclusive cross-section for $Z$ boson production in bins of PHI*. The uncertainties are statistical, systematic, beam and luminosity.
The associated production of a $W$ boson with a jet originating from either a light parton or heavy-flavor quark is studied in the forward region using proton-proton collisions. The analysis uses data corresponding to integrated luminosities of 1.0 and $2.0\,{\rm fb}^{-1}$ collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, respectively. The $W$ bosons are reconstructed using the $W\to\mu\nu$ decay and muons with a transverse momentum, $p_{\rm T}$, larger than 20 GeV in the pseudorapidity range $2.0<\eta<4.5$. The partons are reconstructed as jets with $p_{\rm T} > 20$ GeV and $2.2 < \eta < 4.2$. The sum of the muon and jet momenta must satisfy $p_{\rm T} > 20$ GeV. The fraction of $W+$jet events that originate from beauty and charm quarks is measured, along with the charge asymmetries of the $W\!+\!b$ and $W\!+\!c$ production cross-sections. The ratio of the $W+$jet to $Z+$jet production cross-sections is also measured using the $Z\to\mu\mu$ decay. All results are in agreement with Standard Model predictions.
Summary of the results. All results are reported within a fiducial region that requires a jet with $p_\rm{T} > 20$ GeV in the pseudorapidity range $2.2 < \eta < 4.2$, a muon with $p_\rm{T} > 20$ GeV in the pseudorapidity range $2.0 < \eta < 4.5$, $p_\rm{T}(\mu+j) > 20$ GeV, and $\Delta R(\mu, j) > 0.5$. For $Z+$jet events both muons must fulfill the muon requirements and $60 < M(\mu\mu) < 120$ GeV; the $Z+$jet fiducial region does not require $p_\rm{T}(\mu+j) > 20$ GeV.
A measurement of the cross-section for Z-boson production in the forward region of pp collisions at 8TeV centre-of-mass energy is presented. The measurement is based on a sample of $\rm Z\rightarrow e^+e^-$ decays reconstructed using the LHCb detector, corresponding to an integrated luminosity of 2.0fb$^{-1}$. The acceptance is defined by the requirements $2.0<\eta<4.5$ and $p_{\rm T}>20$GeV for the pseudorapidities and transverse momenta of the leptons. Their invariant mass is required to lie in the range 60--120GeV. The cross-section is determined to be $$ \sigma({\rm pp\to Z\to e^+e^-})=93.81\pm0.41({\rm stat})\pm1.48({\rm syst})\pm1.14({\rm lumi})\;{\rm pb}\,,$$ where the first uncertainty is statistical and the second reflects all systematic effects apart from that arising from the luminosity, which is given as the third uncertainty. Differential cross-sections are presented as functions of the Z-boson rapidity and of the angular variable $\phi^*$, which is related to the Z-boson transverse momentum.
Integrated cross-section for Z$\to$ e$^+$e$^-$ within the LHCb acceptance.
Differential cross-section for Z$\to$ e$^+$e$^-$ as a function of Z-boson rapidity. The first error is statistical, the second the uncorrelated experimental systematic, the third the correlated experimental systematic and the last error is the uncertainty in luminosity. The cross-sections are at the Born level, i.e. before FSR. The rightmost column gives values of the additional factor, $f_{\rm FSR}$, by which the results should be multiplied in order to give the cross-sections after FSR.
Differential cross-section for Z$\to$ e$^+$e$^-$ as a function of $\phi^*$. The first error is statistical, the second the uncorrelated experimental systematic, the third the correlated experimental systematic and the last error is the uncertainty in luminosity. The cross-sections are at the Born level, i.e. before FSR. The rightmost column gives values of the additional factor, $f_{\rm FSR}$, by which the results should be multiplied in order to give the cross-sections after FSR.
The cross-section for inelastic proton-proton collisions, with at least one prompt long-lived charged particle of transverse momentum $p_{\rm T}>0.2$ GeV/$c$ in the pseudorapidity range $2.0<\eta<4.5$, is measured by the LHCb experiment at a centre-of-mass energy of $\sqrt{s}=7$ TeV. The cross-section in this kinematic range is determined to be $\sigma_{\rm inel}^{\rm acc} = 55.0 \pm 2.4$ mb within the spectrometer acceptance with an experimental uncertainty that is dominated by systematic contributions. Extrapolation to the full phase space, using PYTHIA 6, yields $\sigma_{\rm inel} = 66.9 \pm 2.9 \pm 4.4$ mb, where the first uncertainty is experimental and the second is due to the extrapolation.
The cross-section for inelastic $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 7$ TeV, yielding one or more prompt long-lived charged particles in the kinematic range $p_T > 0.2$ GeV/$c$ and $2.0 < \eta < 4.5$ (LHCb acceptance). The quoted uncertainty that is almost completely systematic in nature as the purely statistical uncertainty is two orders of magnitude smaller.
The total cross-section for inelastic $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 7$ TeV, extrapolated using PYTHIA6 and different soft QCD tunes provided by PYTHIA 8.201 to estimate its uncertainty.
A measurement of the inclusive $W \to \mu\nu$ 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 $20 {\rm \, Ge\kern -0.1em V\!/}c$ and pseudorapidity between 2.0 and 4.5. The $W^{+}$ and $W^{-}$ production cross-sections are measured to be $$\sigma_{W^{+} \to \mu^{+}\nu} = 861.0 \pm 2.0 \pm 11.2 \pm 14.7 {\rm \, pb},$$ $$\sigma_{W^{-} \to \mu^{-}\overline{\nu}} = 675.8 \pm 1.9 \pm 8.8 \pm 11.6 {\rm \, pb},$$ 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 $$\frac{\sigma_{W^{+} \to \mu^{+}\nu}}{\sigma_{W^{-} \to \mu^{-}\overline{\nu}}} = 1.274 \pm 0.005 \pm 0.009,$$ 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.
Correction for final state radiation for $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\bar{\nu}$ in bins of muon pseudorapidity. No loss due FSR is observed for $W^-$ in the last pseudorapidity bin because of lack of statistics.
Inclusive cross-section for $W^+$ and $W^-$ boson production in bins of muon pseudorapidity. The uncertainties are statistical, systematic and luminosity.
Ratio of $W^+$ to $W^-$ cross-section in bins of muon pseudorapidity. The uncertainties are statistical and systematic.
The first observation of $Z$ boson production in proton-lead collisions at a centre-of-mass energy per proton-nucleon pair of $\sqrt{s_{NN}}=5~\text{TeV}$ is presented. The data sample corresponds to an integrated luminosity of $1.6~\text{nb}^{-1}$ collected with the LHCb detector. The $Z$ candidates are reconstructed from pairs of oppositely charged muons with pseudorapidities between 2.0 and 4.5 and transverse momenta above $20~\text{GeV}/c$. The invariant dimuon mass is restricted to the range $60-120~\text{GeV}/c^2$. The $Z$ production cross-section is measured to be \begin{eqnarray*} \sigma_{Z\to\mu^+\mu^-}(\text{fwd})&=&13.5^{+5.4}_{-4.0}\text{(stat.)}\pm1.2\text{(syst.)}~\text{nb} \end{eqnarray*} in the direction of the proton beam and \begin{eqnarray*} \sigma_{Z\to\mu^+\mu^-}(\text{bwd}) & =&10.7^{+8.4}_{-5.1}\text{(stat.)}\pm1.0\text{(syst.)}~\text{nb} \end{eqnarray*} in the direction of the lead beam, where the first uncertainty is statistical and the second systematic.
The measured Z production cross-sections in proton-lead collisions, measured in the fiducial region defined in the table, in the forward and backward directions. The statistical uncertainty is defined as the 68% confidence interval with symmetric coverage assuming that the number of candidates follows a Poisson distribution.
The forward-backward ratio measured in the overlap region 2.5 < ABS(YRAP) < 4.0. The first uncertainty is statistical, defined as the 68% confidence interval with symmetric coverage. The second uncertainty is systematic and includes the uncertainty on the acceptance correction factor, BETA, for the difference in the detector acceptance of the muons between the forward and backward directions.