A study of $\chi_{b}$ meson production at LHCb is performed on proton-proton collision data, corresponding to 3.0fb$^{-1}$ of integrated luminosity collected at centre-of-mass energies $\sqrt{s}=7$ and 8TeV. The fraction of $\Upsilon(nS)$ mesons originating from $\chi_{b}$ decays is measured as a function of the $\Upsilon$ transverse momentum in the rapidity range $2.0 < y^{\Upsilon} < 4.5$. The radiative transition of the $\chi_{b}(3P)$ meson to $\Upsilon(3S)$ is observed for the first time. The $\chi_{b1}(3P)$ mass is determined to be $$m(\chi_{b1}(3P)) = 10\,511.3 \pm 1.7 \pm 2.5 MeV/c^2,$$ where the first uncertainty is statistical and the second is systematic.
Fractions $R_{\Upsilon(1S)}^{\chi_{b}(mP)}$ in bins of $p_{\mathrm{T}}^{\Upsilon}$, measured for data collected at $\sqrt{s}= 7$ TeV.
Fractions $R_{\Upsilon(2S)}^{\chi_{b}(mP)}$ in bins of $p_{\mathrm{T}}^{\Upsilon}$, measured for data collected at $\sqrt{s}= 7$ TeV.
Fractions $R_{\Upsilon(3S)}^{\chi_{b}(mP)}$ in bins of $p_{\mathrm{T}}^{\Upsilon}$, measured for data collected at $\sqrt{s}= 7$ TeV.
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.
In this extended analysis using the ZEUS detector at HERA, the photoproduction of isolated photons together with a jet is measured for different ranges of the fractional photon energy, $x_\gamma^{\mathrm{meas}}$, contributing to the photon-jet final state. Cross sections are evaluated in the photon transverse-energy and pseudorapidity ranges $6 < E_T^{\gamma} < 15$ GeV and $-0.7 < \eta^{\gamma} < 0.9$, and for jet transverse-energy and pseudorapidity ranges $4 < E_T^{\rm jet} < 35$ GeV and $-1.5 < \eta^{\rm jet} < 1.8$, for an integrated luminosity of 374 $\mathrm{pb}^{-1}$. The kinematic observables studied comprise the transverse energy and pseudorapidity of the photon and the jet, the azimuthal difference between them, the fraction of proton energy taking part in the interaction, and the difference between the pseudorapidities of the photon and the jet. Higher-order theoretical calculations are compared to the results.
Differential cross-section D(SIG)/DET(GAMMA) for photons in the given X(GAMMA) range accompanied by a jet. The corresponding hadronisation corrections are also given.
Differential cross-section D(SIG)/DETARAP(GAMMA) for photons in the given X(GAMMA) range accompanied by a jet. The corresponding hadronisation corrections are also given.
Differential cross-section D(SIG)/DET(JET) for photons in the given X(GAMMA) range accompanied by a jet. The corresponding hadronisation corrections are also given.
The production of beauty and charm quarks in ep interactions has been studied with the ZEUS detector at HERA for exchanged four-momentum squared 5 < Q^2 < 1000 GeV^2 using an integrated luminosity of 354 pb^{-1}. The beauty and charm content in events with at least one jet have been extracted using the invariant mass of charged tracks associated with secondary vertices and the decay-length significance of these vertices. Differential cross sections as a function of Q^2, Bjorken x, jet transverse energy and pseudorapidity were measured and compared with next-to-leading-order QCD calculations. The beauty and charm contributions to the proton structure functions were extracted from the double-differential cross section as a function of x and Q^2. The running beauty-quark mass, m_b at the scale m_b, was determined from a QCD fit at next-to-leading order to HERA data for the first time and found to be 4.07 \pm 0.14 (fit} ^{+0.01}_{-0.07} (mod.) ^{+0.05}_{-0.00} (param.) ^{+0.08}_{-0.05} (theo) GeV.
Differential cross sections for inclusive jet production in beauty events as a function of ET(JET) for ET(JET) > 5 GeV. The measurements are given together with their statistical and systematic uncertainties. Hadronisation and QED radiative corrections, CHAD and CRAD, respectively, are also shown.
Differential cross sections for inclusive jet production in charm events as a function of ET(JET) for ET(JET) > 4.2 GeV. The measurements are given together with their statistical and systematic uncertainties. Hadronisation and QED radiative corrections, CHAD and CRAD, respectively, are also shown.
Differential cross sections for inclusive jet production in beauty events as a function of ETARAP(JET) for -1.6 < ETARAP(JET) < 2.2. The measurements are given together with their statistical and systematic uncertainties. Hadronisation and QED radiative corrections, CHAD and CRAD, respectively, are also shown.
The photoproduction of $D^{*\pm}$ mesons has been measured with the ZEUS detector at HERA at three different ep centre-of-mass energies, $\sqrt{s}$, of 318, 251 and 225 GeV. For each data set, $D^*$ mesons were required to have transverse momentum, $p_T^{D^*}$, and pseudorapidity, $\eta^{D^*}$, in the ranges $1.9 < p_T^{D^*} < 20$ GeV and $|\eta^{D^*}|<1.6$. The events were required to have a virtuality of the incoming photon, $Q^2$, of less than 1 GeV$^2$. The dependence on $\sqrt{s}$ was studied by normalising to the high-statistics measurement at $\sqrt{s} =318$ GeV. This led to the cancellation of a number of systematic effects both in data and theory. Predictions from next-to-leading-order QCD describe the $\sqrt{s}$ dependence of the data well.
The cross sections for the production of D*+- mesons normalised to the HER data sample.
Production of $\Upsilon$ mesons in proton-lead collisions at a nucleon-nucleon centre-of-mass energy $\sqrt{s_{NN}}=5 \mathrm{TeV}$ is studied with the LHCb detector. The analysis is based on a data sample corresponding to an integrated luminosity of $1.6 \mathrm{nb}^{-1}$. The $\Upsilon$ mesons of transverse momenta up to $15 \mathrm{GeV}/c$ are reconstructed in the dimuon decay mode. The rapidity coverage in the centre-of-mass system is $1.5 < y < 4.0$ (forward region) and $-5.0 < y < -2.5$ (backward region). The forward-backward production ratio and the nuclear modification factor for $\Upsilon(1S)$ mesons are determined. The data are compatible with the predictions for a suppression of $\Upsilon(1S)$ production with respect to proton-proton collisions in the forward region, and an enhancement in the backward region. The suppression is found to be smaller than in the case of prompt $J/\psi$ mesons.
The product of production cross-section and branching fraction for upsilon mesons in the backward and forward regions.
The product of production cross-section and branching fraction for UPSILON(1S) in the common rapidity range.
The production ratios of excited upsilon mesons in the backward and forward regions.
The reduced cross sections for $e^{+}p$ deep inelastic scattering have been measured with the ZEUS detector at HERA at three different centre-of-mass energies, $318$, $251$ and $225$ GeV. The cross sections, measured double differentially in Bjorken $x$ and the virtuality, $Q^2$, were obtained in the region $0.13\ \leq\ y\ \leq\ 0.75$, where $y$ denotes the inelasticity and $5\ \leq\ Q^2\ \leq\ 110$ GeV$^2$. The proton structure functions $F_2$ and $F_L$ were extracted from the measured cross sections.
The reduced cross section for the reaction E+ P --> E+ X at a centre-of-mass energy 318 GeV and Q^2=7 GeV^2 for the central-vertex region. The (sys) error shown in the table is the total systematic uncertainty, excluding the normalisation uncertainties shown separately below.
The reduced cross section for the reaction E+ P --> E+ X at a centre-of-mass energy 318 GeV and Q^2=9 GeV^2 for the central-vertex region. The (sys) error shown in the table is the total systematic uncertainty, excluding the normalisation uncertainties shown separately below.
The reduced cross section for the reaction E+ P --> E+ X at a centre-of-mass energy 318 GeV and Q^2=12 GeV^2 for the central-vertex region. The (sys) error shown in the table is the total systematic uncertainty, excluding the normalisation uncertainties shown separately below.
The polarisation of prompt $\psi(2S)$ mesons is measured by performing an angular analysis of $\psi(2S)\rightarrow \mu^{+} \mu^{-}$ decays using proton-proton collision data, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the LHCb detector at a centre-of-mass energy of 7 TeV. The polarisation is measured in bins of transverse momentum $p_\mathrm{T}$ and rapidity $y$ in the kinematic region $3.5<p_\mathrm{T}<15$ GeV$/c$ and $2.0<y<4.5$, and is compared to theoretical models. No significant polarisation is observed.
The measured prompt PSI(2S) polarisation parameter LAMBDA(THETA) in bins of YRAP and PT in the helicity frame.
The measured prompt PSI(2S) polarisation parameter LAMBDA(THETA PHI) in bins of YRAP and PT in the helicity frame.
The measured prompt PSI(2S) polarisation parameter LAMBDA(PHI) in bins of YRAP and PT in the helicity frame.
Charged particle multiplicities are studied in proton-proton collisions in the forward region at a centre-of-mass energy of $\sqrt{s} = 7\;$TeV with data collected by the LHCb detector. The forward spectrometer allows access to a kinematic range of $2.0<\eta<4.8$ in pseudorapidity, momenta down to $2\;$GeV/$c$ and transverse momenta down to $0.2\;$GeV/$c$. The measurements are performed using minimum-bias events with at least one charged particle in the kinematic acceptance. The results are presented as functions of pseudorapidity and transverse momentum and are compared to predictions from several Monte Carlo event generators.
Charged particle density as function of pseudorapidity for events with at least one prompt final state charged particle in fiducial range. The first quoted uncertainty is statistical and the second systematic.
Charged particle density as function of transverse momentum for events with at least one prompt final state charged particle in fiducial range. The first quoted uncertainty is statistical and the second systematic.
Observed charged particle multiplicity distribution in the full kinematic range of the analysis. The first quoted uncertainty is statistical and the second systematic.
The production of Upsilon(1S), Upsilon(2S) and Upsilon(3S) mesons decaying into the dimuon final state is studied with the LHCb detector using a data sample corresponding to an integrated luminosity of 3.3 pb^{-1} collected in proton-proton collisions at a centre-of-mass energy of sqrt{s}=2.76 TeV. The differential production cross-sections times dimuon branching fractions are measured as functions of the Upsilon transverse momentum and rapidity, over the ranges p_T<15 GeV/c and 2.0<y<4.5. The total cross-sections in this kinematic region, assuming unpolarised production, are measured to be sigma(pp -> Upsilon(1S) X) x B(Upsilon(1S) -> mu+mu-) = 1.111 +/- 0.043 +/- 0.044 nb, sigma(pp -> Upsilon(2S) X) x B(Upsilon(2S) -> mu+mu-) = 0.264 +/- 0.023 +/- 0.011 nb, sigma(pp -> Upsilon(3S) X) x B(Upsilon(3S) -> mu+mu-) = 0.159 +/- 0.020 +/- 0.007 nb, where the first uncertainty is statistical and the second systematic.
Integrated cross-sections times dimuon branching fractions in the PT range < 15 GeV and rapidity in the range 2.0-4.5. The first uncertainty is statistical and the second systematic.
Integrated cross-sections times dimuon branching fractions in the PT range < 15 GeV and rapidity in the range 2.5-4.0. The first uncertainty is statistical and the second systematic.
Single differential cross-section for UPSI(1S) times the dimuon branching fraction as a function of PT for the rapidity region 2.0-4.5 without normalisation to the bin sizes. The first uncertainty is statistical and the second systematic.
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