The prompt and non-prompt production cross-sections for $\psi(2S)$ mesons are measured using 2.1 fb$^{-1}$ of $pp$ collision data at a centre-of-mass energy of 7 TeV recorded by the ATLAS experiment at the LHC. The measurement exploits the $\psi(2S)\to J/\psi(\to\mu^+\mu^-)\pi^+\pi^-$ decay mode, and probes $\psi(2S)$ mesons with transverse momenta in the range $10\leq p_T<100$ GeV and rapidity $|y|<2.0$. The results are compared to other measurements of $\psi(2S)$ production at the LHC and to various theoretical models for prompt and non-prompt quarkonium production.
Non-prompt $\psi(2\mathrm{S})$ production fraction as a function of $\psi(2\mathrm{S})$ $p_{\rm T}$ for $\psi(2\mathrm{S})$ rapidity interval of $0\leq |y| < 0.75$. The first uncertainty is statistical, the second is systematic. Spin-alignment uncertainties are not included.
Non-prompt $\psi(2\mathrm{S})$ production fraction as a function of $\psi(2\mathrm{S})$ $p_{\rm T}$ for $\psi(2\mathrm{S})$ rapidity interval of $0.75\leq |y| < 1.5$. The first uncertainty is statistical, the second is systematic. Spin-alignment uncertainties are not included.
Non-prompt $\psi(2\mathrm{S})$ production fraction as a function of $\psi(2\mathrm{S})$ $p_{\rm T}$ for $\psi(2\mathrm{S})$ rapidity interval of $1.5\leq |y| < 2$. The first uncertainty is statistical, the second is systematic. Spin-alignment uncertainties are not included.
The inclusive top quark pair ($t\bar{t}$) production cross-section $\sigma_{t\bar{t}}$ has been measured in $pp$ collisions at $\sqrt{s}=7$ TeV and $\sqrt{s}=8$ TeV with the ATLAS experiment at the LHC, using $t\bar{t}$ events with an opposite-charge $e\mu$ pair in the final state. The measurement was performed with the 2011 7 TeV dataset corresponding to an integrated luminosity of 4.6 fb$^{-1}$ and the 2012 8 TeV dataset of 20.3 fb$^{-1}$. The cross-section was measured to be: $\sigma_{t\bar{t}}=182.9\pm 3.1\pm 4.2\pm 3.6 \pm 3.3$ pb ($\sqrt{s}=7$ TeV) and $\sigma_{t\bar{t}}=242.9\pm 1.7\pm 5.5\pm 5.1\pm 4.2$ pb ($\sqrt{s}=8$ TeV, updated as described in the Addendum), where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the knowledge of the integrated luminosity and of the LHC beam energy. The results are consistent with recent theoretical QCD calculations at next-to-next-to-leading order. Fiducial measurements corresponding to the experimental acceptance of the leptons are also reported, together with the ratio of cross-sections measured at the two centre-of-mass energies. The inclusive cross-section results were used to determine the top quark pole mass via the dependence of the theoretically-predicted cross-section on $m_t^{\rm pole}$, giving a result of $m_t^{\rm pole}=172.9^{+2.5}_{-2.6}$ GeV. By looking for an excess of $t\bar{t}$ production with respect to the QCD prediction, the results were also used to place limits on the pair-production of supersymmetric top squarks $\tilde{t}_1$ with masses close to the top quark mass decaying via $\tilde{t}_1\rightarrow t\tilde{\chi}^0_1$ to predominantly right-handed top quarks and a light neutralino $\tilde{\chi}_0^1$, the lightest supersymmetric particle. Top squarks with masses between the top quark mass and 177 GeV are excluded at the 95% confidence level.
95% CL exclusion limit on signal strength.
95% CL exclusion limit on signal cross section for the 7 TeV dataset.
95% CL exclusion limit on signal cross section for the 8 TeV dataset.
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.
The production of a W boson in association with a single charm quark is studied using 4.6 fb^-1 of pp collision data at sqrt(s)=7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96 +0.26 -0.30 at Q^2=1.9 GeV^2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio sigma(W^+ + bar{c})/sigma(W^- + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s-bar{s} quark asymmetry.
Measured integrated cross sections of the production of a W boson with a single c-jet, a D meson or a D* meson times the branching ratio W -> l nu in the fiducial regions together with the statistical and systematic uncertainties. For the W+c-jet cross sections events with more than one c-jet are discarded. The particle-level c-jet is defined as the one containing a weakly decaying c-hadron with pt>5 GeV, within DeltaR<0.3. Jets containing c-hadrons originating from b-hadron decays are not counted as c-jets. Jets are not required for the W+D/D* cross sections. The cross sections are defined for OS-SS events.
Measured integrated cross section ratios of the production of W+ and W- bosons associated with a single c-jet, a D meson or a D* meson in the fiducial regions together with the statistical and systematic uncertainties. For the W+c-jet cross sections events with more than one c-jet are discarded. The particle-level c-jet is defined as the one containing a weakly decaying c-hadron with pt>5 GeV, within DeltaR<0.3. Jets containing c-hadrons originating from b-hadron decays are not counted as c-jets. Jets are not required for the W+D/D* cross sections. The cross sections are defined for OS-SS events.
Measured differential cross sections as function of the lepton pseudo-rapidity of the production of a W boson with a single c-jet times the branching ratio W -> l nu in the fiducial regions together with the statistical and systematic uncertainties. For the W+c-jet cross sections events with more than one c-jet are discarded. The particle-level c-jet is defined as the one containing a weakly decaying c-hadron with pt>5 GeV, within DeltaR<0.3. Jets containing c-hadrons originating from b-hadron decays are not counted as c-jets. The cross sections are defined for OS-SS events.
The production of J/psi and Upsilon mesons in pp collisions at sqrt(s) = 8 TeV is studied with the LHCb detector. The J/psi and Upsilon mesons are reconstructed in the mu+mu- decay mode and the signal yields are determined with a fit to the mu+mu- invariant mass distributions. The analysis is performed in the rapidity range 2.0<y<4.5 and transverse momentum range 0<p_T<14(15) GeV/c of the J/psi(Upsilon) mesons. The J/psi and Upsilon production cross-sections and the fraction of J/psi mesons from b-hadron decays are measured as a function of the meson p_T and y.
The total integrated cross sections for prompt J/PSI production, assuming no polarisation, and J/PSI production from b-hadron decays in the rapidity range 2.0-4.5 and transverse momentum 0-14 GeV/c;.
Differential production cross section in rapidity for prompt J/PSI mesons (assuming no polarisation) and from J/PSI from b-hadron decays.;.
The double-differential cross sections for prompt J/PSI production (assuming no polarisation) and production of J/PSI from b-hadron decays as a function of transverse momentum for the rapidity range 2.0-2.5. Also shown in the final column is the fraction (in %) of J/PSIs from the latter.
Using 1.8 fb-1 of pp collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the Large Hadron Collider, we present measurements of the production cross sections of Upsilon(1S,2S,3S) mesons. Upsilon mesons are reconstructed using the di-muon decay mode. Total production cross sections for p_T<70 GeV and in the rapidity interval |Upsilon|<2.25 are measured to be 8.01+-0.02+-0.36+-0.31 nb, 2.05+-0.01+-0.12+-0.08 nb, 0.92+-0.01+-0.07+-0.04 nb respectively, with uncertainties separated into statistical, systematic, and luminosity measurement effects. In addition, differential cross section times di-muon branching fractions for Upsilon(1S), Upsilon(2S), and Upsilon(3S) as a function of Upsilon transverse momentum p_T and rapidity are presented. These cross sections are obtained assuming unpolarized production. If the production polarization is fully transverse or longitudinal with no azimuthal dependence in the helicity frame the cross section may vary by approximately +-20%. If a non-trivial azimuthal dependence is considered, integrated cross sections may be significantly enhanced by a factor of two or more. We compare our results to several theoretical models of Upsilon meson production, finding that none provide an accurate description of our data over the full range of Upsilon transverse momenta accessible with this dataset.
Corrected cross-section measurements in the isotopic spin-alignment scenario. The second (sys) error is the uncertainty in the luminosity.
Fiducial Upsilon(1S) production cross-section, where pT>4 GeV and |eta|<2.3 for both muons, as a function of Upsilon(1S) pT in the Upsilon(1S) rapidity (|y|) bins 0-1.2 and 1.2-2.25. The first uncertainty is statistical, the second is systematic.
Fiducial Upsilon(2S) production cross-section, where pT>4 GeV and |eta|<2.3 for both muons, as a function of Upsilon(2S) pT in the Upsilon(2S) rapidity (|y|) bins 0-1.2 and 1.2-2.25. The first uncertainty is statistical, the second is systematic.
The production of Upsilon(1S), Upsilon(2S) and Upsilon(3S) mesons in proton-proton collisions at the centre-of-mass energy of sqrt(s)=7 TeV is studied with the LHCb detector. The analysis is based on a data sample of 25 pb-1 collected at the Large Hadron Collider. The Upsilon mesons are reconstructed in the decay mode Upsilon -> mu+ mu- and the signal yields are extracted from a fit to the mu+ mu- invariant mass distributions. The differential production cross-sections times dimuon branching fractions are measured as a function of the Upsilon transverse momentum pT and rapidity y, over the range pT < 15 GeV/c and 2.0 < y < 4.5. The cross-sections times branching fractions, integrated over these kinematic ranges, are measured to be sigma(pp -> Upsilon(1S) X) x B(Upsilon(1S)->mu+ mu-) = 2.29 {\pm} 0.01 {\pm} 0.10 -0.37 +0.19 nb, sigma(pp -> Upsilon(2S) X) x B(Upsilon(2S)->mu+ mu-) = 0.562 {\pm} 0.007 {\pm} 0.023 -0.092 +0.048 nb, sigma(pp -> Upsilon(3S) X) x B(Upsilon(3S)->mu+ mu-) = 0.283 {\pm} 0.005 {\pm} 0.012 -0.048 +0.025 nb, where the first uncertainty is statistical, the second systematic and the third is due to the unknown polarisation of the three Upsilon states.
Integrated cross-sections times dimuon branching fractions in the PT range < 15 GeV/c and rapidity in the range 2.0-4.0. The second systematic (sys) error is due to the unknown polarisation of the three states.
Double differential cross section for UPSI(1S) production times the dimuon branching fraction as a function of PT for the rapidity region 2.0-2.5. The second systematic (sys) error is due to the unknown polarisation of the UPSI(1S).
Double differential cross section for UPSI(1S) production times the dimuon branching fraction as a function of PT for the rapidity region 2.5-3.0. The second systematic (sys) error is due to the unknown polarisation of the UPSI(1S).
psi' production is studied in Pb-Pb collisions at 158 GeV/c per nucleon incident momentum. Absolute cross-sections are measured and production rates are investigated as a function of the centrality of the collision. The results are compared with those obtained for lighter colliding systems and also for the J/psi meson produced under identical conditions.
Inclusive cross sections for PSI(3685) and J/PSI, multiplied by their Branching ratios into MU+MU-,.
Inclusive cross sections for Drell Yan in the 4.2-7 GeV/c** mass range.
Inclusive cross sections for PSI(3685) and J/PSI, multiplied by theirBransching ratios into MU+MU-, and for Drell Yan in the 4.2-7 GeV/c** massrange.
Ratios of the Psi' over the J/psi production cross sections in the dilepton channel for C, Ti and W targets have been measured in 920 GeV proton-nucleus interactions with the HERA-B detector at the HERA storage ring. The Psi' and J/psi states were reconstructed in both the mu+mu- and the e+e- decay modes. The measurements covered the kinematic range -0.35 < x_F < 0.1 with transverse momentum p_T < 4.5 GeV/c. The Psi' to J/psi production ratio is almost constant in the covered x_F range and shows a slow increase with p_T. The angular dependence of the ratio has been used to measure the difference of the Psi' and J/psi polarization. All results for the muon and electron decay channels are in good agreement: their ratio, averaged over all events, is R_psi'(mu)/R_psi'(e)=1.00+-0.08+-0.04. This result constitutes a new, direct experimental constraint on the double ratio of branching fractions, (B'(mu)*B(e))/(B(mu)*B'(e)), of Psi' and J/psi in the two channels.
Ratio of PSI(3685) and J/PSI cross sections for both muon and electron channels combined, obtained for different cos theta in the s-channel helicity frame.
Ratio of PSI(3685) and J/PSI cross sections for both muon and electron channels combined, obtained for intervals inpT using the data from all targets.
Ratio of PSI(3685) and J/PSI production cross sections per nucleus.
We present a new measurement of J/psi production in Pb-Pb collisions at 158 GeV/nucleon, from the data sample collected in year 2000 by the NA50 Collaboration, under improved experimental conditions with respect to previous years. With the target system placed in vacuum, the setup was better adapted to study, in particular, the most peripheral nuclear collisions with unprecedented accuracy. The analysis of this data sample shows that the (J/psi)/Drell-Yan cross-sections ratio measured in the most peripheral Pb-Pb interactions is in good agreement with the nuclear absorption pattern extrapolated from the studies of proton-nucleus collisions. Furthermore, this new measurement confirms our previous observation that the (J/psi)/Drell-Yan cross-sections ratio departs from the normal nuclear absorption pattern for semi-central Pb-Pb collisions and that this ratio persistently decreases up to the most central collisions.
Centrality classes based on the transverse energy measurement Errors are rms values obtained with fit.
Cross sections ratio J/PSI/Drell-Yan as a function of ET IN GEV obtained withthe ET Centrality estimator.
Cross sections ratio J/PSI/Drell-Yan as a function of NPART obtained withthe ET Centrality estimator.
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