The cross-section for prompt antiproton production in collisions of protons with an energy of $6.5$ TeV incident on helium nuclei at rest is measured with the LHCb experiment from a data set corresponding to an integrated luminosity of $0.5\,nb^{-1}$. The target is provided by injecting helium gas into the LHC beam line at the LHCb interaction point. The reported results, covering antiproton momenta between $12$ and $110\,\mathrm{GeV/}c$, represent the first direct determination of the antiproton production cross-section in ${\rm p He}$ collisions, and impact the interpretation of recent results on antiproton cosmic rays from space-borne experiments.
Double-differential cross-section in antiproton momentum and transverse momentum for antiproton production in collisions of 6.5 TeV protons on He nuclei at rest. The antiproton momentum is defined in the laboratory frame. Results are averaged over the given kinematic range of each bin. The uncertainty is split into an uncertainty delta_uncorr, uncorrelated among the kinematic bins, and an uncertainty delta_corr, fully correlated among the kinematic bins. For both uncertainties, the systematic uncertainty, dominant for most bins, and the statistical uncertainty, are added in quadrature. The average value within each bin is also reported for the antiproton momentum, the transverse momentum, and x-Feynman xF=2 p_Z*/SQRT(S), where p_Z* is the longitudinal antiproton momentum in the center-of-mass system and SQRT(S) the nucleon-nucleon center-of-mass energy. These average values are obtained from simulation (based on EPOS LHC), to avoid biases from reconstruction effects and given the good agreement with data observed for the simulated kinematic spectra.
Double-differential cross-section in antiproton momentum and transverse momentum for antiproton production in collisions of 6.5 TeV protons on He nuclei at rest. The antiproton momentum is defined in the laboratory frame. Results are averaged over the given kinematic range of each bin. The uncertainty is split into an uncertainty delta_uncorr, uncorrelated among the kinematic bins, and an uncertainty delta_corr, fully correlated among the kinematic bins. For both uncertainties, the systematic uncertainty, dominant for most bins, and the statistical uncertainty, are added in quadrature. The average value within each bin is also reported for the antiproton momentum, the transverse momentum, and x-Feynman xF=2 p_Z*/SQRT(S), where p_Z* is the longitudinal antiproton momentum in the center-of-mass system and SQRT(S) the nucleon-nucleon center-of-mass energy. These average values are obtained from simulation (based on EPOS LHC), to avoid biases from reconstruction effects and given the good agreement with data observed for the simulated kinematic spectra.
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.
Systematic uncertainties in the double differential cross-sections in interval regions of $y^{Z}$ and $p_{T}^{Z}$, presented in percentage. The contributions from efficiency (Eff), background (BKG), final state radiation (FSR), closure test (Closure), and alignment and calibration (Alignment) are shown.
We present an angular analysis of the $B^{+}\rightarrow K^{\ast+}(\rightarrow K_{S}^{0}\pi^{+})\mu^{+}\mu^{-}$ decay using 9$\,\mbox{fb}^{-1}$ of $pp$ collision data collected with the LHCb experiment. For the first time, the full set of CP-averaged angular observables is measured in intervals of the dimuon invariant mass squared. Local deviations from Standard Model predictions are observed, similar to those in previous LHCb analyses of the isospin-partner $B^{0}\rightarrow K^{\ast0}\mu^{+}\mu^{-}$ decay. The global tension is dependent on which effective couplings are considered and on the choice of theory nuisance parameters.
Correlation matrix for the optimised observables FL and P1–P'8 from the maximum-likelihood fit in the interval 15.00 < q2 < 19.00 GeV2/c4
The production of $W$ and $Z$ bosons in association with jets is studied in the forward region of proton-proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98 $\pm$ 0.02 fb$^{-1}$. The $W$ boson is identified using its decay to a muon and a neutrino, while the $Z$ boson is identified through its decay to a muon pair. Total cross-sections are measured and combined into charge ratios, asymmetries, and ratios of $W+$jet and $Z$+jet production cross-sections. Differential measurements are also performed as a function of both boson and jet kinematic variables. All results are in agreement with Standard Model predictions.
The correlation matrix for the systematic uncertainties on the $W^+j$, $W^-j$ and $Zj$ production cross-section measurements presented in Tables 2 and 5 in bins of $\eta^{\rm jet}$. The first four rows/columns correspond to the $W^+j$ cross-section in bins of $\eta^{\rm jet}$, the middle four correspond to the $W^-j$ cross-section in bins of $\eta^{\rm jet}$ and the final four correspond to the $Zj$ cross-section in bins of $\eta^{\rm jet}$. The matrix is used to calculate the ratios of $Wj$ to $Zj$ production and the charge ratio and asymmetry of $Wj$ production in the total fiducial region.
The correlation matrix for the systematic uncertainties on the $W^+j$, $W^-j$ and $Z^0 j$ production cross-section measurements presented in Tables 2 and 5 in bins of $\eta^{\rm jet}$. The matrix is used to calculate the ratios of $Wj$ to $Z^0 j$ production and the charge ratio and asymmetry of $Wj$ production in the total fiducial region.
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.
The polarization of the $\Upsilon(1S)$, $\Upsilon(2S)$ and $\Upsilon(3S) $mesons, produced in $pp$ collisions at centre-of-mass energies $\sqrt{s}$=7 and 8TeV, is measured using data samples collected by the LHCb experiment, corresponding to integrated luminosities of 1 and 2fb$^{-1}$, respectively. The measurements are performed in three polarization frames, using $\Upsilon\to\mu^+\mu^-$ decays in the kinematic region of the transverse momentum $p_{T}(\Upsilon)<30GeV/c$, and rapidity $2.2<y(\Upsilon)<4.5$. No large polarization is observed.
The polarization parameter $\lambda_{\theta\phi}$ measured in the Gottfried-Jackson frame for the $\Upsilon(1S)$ state in different bins of $p_{T}^{\Upsilon}$ and three rapidity ranges using data collected at $\sqrt{s}=8\,\mathrm{TeV}$. The first quoted uncertainty is statistical and the second is systematic.
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.
Differential cross-section of $J/\psi$ pair as a function of $M(J/\psi J/\psi)$ for $p_{T}(J/\psi J/\psi)>3$ GeV$/c$.
Measurements of the cross-section for producing \bquark quarks in the reaction $pp\to b\bar{b} X$ are reported in 7 and 13 TeV collisions at the LHC as a function of the pseudorapidity $\eta$ in the range $2<\eta<5$ covered by the acceptance of the LHCb experiment. The measurements are done using semileptonic decays of $b$-flavored hadrons decaying into a ground-state charmed hadron in association with a muon. The cross-sections in the covered $\eta$ range are $72.0\pm 0.3\pm6.8~\mu$b and $144\pm 1\pm 21~\mu$b for 7 and 13 TeV. The ratio is $2.00\pm0.02\pm0.26$, where the quoted uncertainties are statistical and systematic, respectively. The agreement with theoretical expectation is good at 7 TeV, but differs somewhat at 13 TeV. The measured ratio of cross-sections is larger at lower $\eta$ than the model prediction.
The cross-section as a function of $\eta$ for $pp \to H_b X$, where $H_b$ is a hadron that contains either a $b$ or a $\bar{b}$ quark, but not both, at center-of-mass energy of 7 TeV. The first uncertainty is statistical and the second systematic. To get the differential cross-section in each interval multiply by a factor two.
The cross-section as a function of $\eta$ for $pp \to H_b X$, where $H_b$ is a hadron that contains either a $b$ or a $\bar{b}$ quark, but not both, at center-of-mass energy of 13 TeV. The first uncertainty is statistical and the second systematic. To get the differential cross-section in each interval multiply by a factor two.
An angular analysis of the $B^{0}\rightarrow K^{*0}(\rightarrow K^{+}\pi^{-})\mu^{+}\mu^{-}$ decay is presented. The dataset corresponds to an integrated luminosity of $3.0\,{\mbox{fb}^{-1}}$ of $pp$ collision data collected at the LHCb experiment. The complete angular information from the decay is used to determine $C\!P$-averaged observables and $C\!P$ asymmetries, taking account of possible contamination from decays with the $K^{+}\pi^{-}$ system in an S-wave configuration. The angular observables and their correlations are reported in bins of $q^2$, the invariant mass squared of the dimuon system. The observables are determined both from an unbinned maximum likelihood fit and by using the principal moments of the angular distribution. In addition, by fitting for $q^2$-dependent decay amplitudes in the region $1.1<q^{2}<6.0\mathrm{\,Ge\kern -0.1em V}^{2}/c^{4}$, the zero-crossing points of several angular observables are computed. A global fit is performed to the complete set of $C\!P$-averaged observables obtained from the maximum likelihood fit. This fit indicates differences with predictions based on the Standard Model at the level of 3.4 standard deviations. These differences could be explained by contributions from physics beyond the Standard Model, or by an unexpectedly large hadronic effect that is not accounted for in the Standard Model predictions.
Likelihood correlation matrix $4.0 <q^2< 6.0~{\rm GeV}^2/c^4$.
The production of $\Upsilon$ mesons in $pp$ collisions at $\sqrt=7$ and $8\,\mathrm{TeV}$ is studied with the LHCb detector using data samples corresponding to an integrated luminosity of $1\,\mathrm{fb}^{-1}$ and $2\,\mathrm{fb}^{-1}$ respectively. The production cross-sections and ratios of cross-sections are measured as functions of the meson transverse momentum $p_T$ and rapidity $y$, for $p_T<30\,\mathrm{GeV}/c$} and $2.0<y<4.5$.
The ratio of differential cross-section $\mathrm{d} \sigma ( pp \to ( \Upsilon \to \mu^+ \mu^- ) X ) / \mathrm{d}y$ for $\sqrt{s}=8$ and $\sqrt{s}=7$ TeV and $p_T < 30$ GeV/$c$.
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 $Z$ boson production in bins of muon pseudorapidity at centre-of-mass energy of 7 TeV. The uncertainties are statistical, systematic, beam and luminosity.
$W^{\pm}$ to $Z$ boson cross-section ratio in bins of muon pseudorapidity at centre-of-mass energy of 7 TeV. The uncertainties are statistical, systematic, beam and luminosity.
Correlation coefficients of differential cross-section measurements as a function of lepton $\eta$. The beam energy and luminosity uncertainties, which are fully correlated between cross-section measurements, are excluded. This table lists bin-to-bin correlations for $W^{+}$.
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.
Correlation coefficients of differential cross-section measurements as a function of $y_{Z}$. The beam energy and luminosity uncertainties, which are fully correlated between cross-section measurements, are excluded.
Correlation coefficients of differential cross-section measurements as a function of transverse momentum. The beam energy and luminosity uncertainties, which are fully correlated between cross-section measurements, are excluded.
Correlation coefficients of differential cross-section measurements as a function of $\phi^{*}$. The beam energy and luminosity uncertainties, which are fully correlated between cross-section measurements, are excluded.
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.
The production of $J/\psi$ mesons accompanied by open charm, and of pairs of open charm hadrons are observed in pp collisions at a centre-of-mass energy of 7 TeV using an integrated luminosity of $355pb^{-1}$ collected with the LHCb detector. Model independent measurements of absolute cross-sections are given together with ratios to the measured $J/\psi$ and open charm cross-sections. The properties of these events are studied and compared to theoretical predictions.
Normalized differential cross-section $\frac{d\ln\sigma\left(pp\rightarrow J/\psi D^+ X \right)}{d \left| \Delta \phi/\pi \right|}$ for $2<y(J/\psi)<4$, $p_T(J/\psi)<12$ GeV/$c$, $2<y(D^+)<4$, $3<p_T(D^+)<12$ GeV/$c$ region.
The energy flow created in pp collisions at is studied within the pseudorapidity range 1.9<η<4.9 with data collected by the LHCb experiment. The measurements are performed for inclusive minimum-bias interactions, hard scattering processes and events with an enhanced or suppressed diffractive contribution. The results are compared to predictions given by Pythia-based and cosmic-ray event generators, which provide different models of soft hadronic interactions.
Charged energy flow for inclusive mininum bias events, requiring at least one charged particle in the pseudorapidity range 1.9 < eta < 4.9.
Charged energy flow for hard scattering events, requiring at least one charged particle with transverse momentum > 3 GeV and in the pseudorapidity range 1.9 < eta < 4.9.
Charged energy flow for diffractive enriched events, requiring no charged particles in the pseudorapidity range -3.5 < eta < -1.5 and at least one charged particle in the pseudorapidity range 1.9 < eta < 4.9.
Charm production at the LHC in pp collisions at sqrt(s)=7 TeV is studied with the LHCb detector. The decays D0 -> K- pi+, D+ -> K- pi+ pi+, D*+ -> D0(K- pi+) pi+, D_s+ -> phi(K- K+) pi+, Lambda_c+ -> p K- pi+, and their charge conjugates are analysed in a data set corresponding to an integrated luminosity of 15 nb^{-1}. Differential cross-sections dsigma/dp_T are measured for prompt production of the five charmed hadron species in bins of transverse momentum and rapidity in the region 0 < p_T < 8 GeV/c and 2.0 < y < 4.5. Theoretical predictions are compared to the measured differential cross-sections. The integrated cross-sections of the charm hadrons are computed in the above p_T-y range, and their ratios are reported. A combination of the five integrated cross-section measurements gives sigma(c\bar{c})_{p_T < 8 GeV/c, 2.0 < y < 4.5} = 1419 +/- 12 (stat) +/- 116 (syst) +/- 65 (frag) microbarn, where the uncertainties are statistical, systematic, and due to the fragmentation functions.
Differential production cross-sections with respect to transverse momentum, dsigma / dp_T, of Lambda_c+ baryons or their charge conjugates in proton-proton collisions at center-of-mass (CM) energy sqrt(s) = 7 TeV. Measured in bins of hadron transverse momentum (p_T) and rapidity (y) with respect to the beam axis, where p_T and y are measured in the CM frame. Contributions of charm hadrons from the decays of b-hadrons have been removed.
Differential production cross-sections with respect to transverse momentum, dsigma / dp_T, of D0 mesons or their charge conjugates in proton-proton collisions at center-of-mass (CM) energy sqrt(s) = 7 TeV. Measured in bins of hadron transverse momentum (p_T) and rapidity (y) with respect to the beam axis, where p_T and y are measured in the CM frame. Contributions of charm hadrons from the decays of b-hadrons have been removed.
Differential production cross-sections with respect to transverse momentum, dsigma / dp_T, of D+ mesons or their charge conjugates in proton-proton collisions at center-of-mass (CM) energy sqrt(s) = 7 TeV. Measured in bins of hadron transverse momentum (p_T) and rapidity (y) with respect to the beam axis, where p_T and y are measured in the CM frame. Contributions of charm hadrons from the decays of b-hadrons have been removed.
Decays of $b$ hadrons into final states containing a $D^0$ meson and a muon are used to measure the $b\bar{b}$ production cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC. In the pseudorapidity interval $2 < \eta < 6$ and integrated over all transverse momenta we find that the average cross-section to produce $b$-flavoured or $\bar{b}$-flavoured hadrons is ($75.3 \pm 5.4 \pm 13.0$) microbarns.
The cross section for b-flavoured hadrons (HADRON/B) as a function of pseudorapidity in proton-proton collisions at a centre-of-mass energy of 7 TeV. Cross sections are shown using fragmentation fractions both from LEP and from the Tevatron. See comment above regarding this latter point.
The cross section for b-flavoured hadrons (HADRON/B) over the pseudorapidity range 2.0-6.0 in proton-proton collisions at a centre-of-mass energy of 7 TeV. Cross sections are shown using fragmentation fractions both from LEP and from the Tevatron. See comment above regarding this latter point.
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