The cross section for the production of Z gamma in proton-proton collisions at 8 TeV is measured based on data collected by the CMS experiment at the LHC corresponding to an integrated luminosity of 19.5 inverse femtobarns. Events with an oppositely-charged pair of muons or electrons together with an isolated photon are selected. The differential cross section as a function of the photon transverse momentum is measured inclusively and exclusively, where the exclusive selection applies a veto on central jets. The observed cross sections are compatible with the expectations of next-to-next-to-leading-order quantum chromodynamics. Limits on anomalous triple gauge couplings of Z Z gamma and Z gamma gamma are set that improve on previous experimental results obtained with the charged lepton decay modes of the Z boson.
Inclusive fiducial cross sections in bins of pT(gamma) with statistical, systematic, and luminosity uncertainties, respectivley. Results are not divided by bin-widths. The last bin is the cross section for pT(gamma) > 120 GeV. Combined result of electron and muon channels.
Fiducial cross sections with jet-veto in bins of pT(gamma) with statistical, systematic, and luminosity uncertainties, respectivley. Results are not divided by bin-widths. The last bin is the cross section for pT(gamma) > 120 GeV. Combined result of electron and muon channels.
Ratio of fiducial cross section with jet-veto and the inclusive cross section in bins of pT(gamma). The last bin is the cross section for pT(gamma) > 120 GeV. Combined result of electron and muon channels.
The double-differential cross sections of promptly produced J/psi and psi(2S) mesons are measured in pp collisions at sqrt(s) = 7 TeV, as a function of transverse momentum pt and absolute rapidity abs(y). The analysis uses J/psi and psi(2S) dimuon samples collected by CMS, corresponding to integrated luminosities of 4.55 and 4.90 inverse femtobarns, respectively. The results are based on a two-dimensional analysis of the dimuon invariant mass and decay length, and extend to pt = 120 and 100 GeV for the J/psi and psi(2S), respectively, when integrated over the interval abs(y) < 1.2. The ratio of the psi(2S) to J/psi cross sections is also reported for abs(y) < 1.2, over the range 10 < pt < 100 GeV. These are the highest pt values for which the cross sections and ratio have been measured.
J/psi double-differential cross section times branching fraction assuming unpolarized production as a function of pT and y for 0.0 < |y| < 0.3, 0.3 < |y| < 0.6, 0.6 < |y| < 0.9 and 0.9 < |y| < 1.2.
psi(2S) double-differential cross section times branching fraction assuming unpolarized production as a function of pT and y for 0.0 < |y| < 0.3, 0.3 < |y| < 0.6, 0.6 < |y| < 0.9 and 0.9 < |y| < 1.2.
J/psi double-differential cross section times branching fraction and the corresponding scaling factors to obtain the cross sections for different polarization scenarios (azimuthal polarization parameter in the center of mass helicity frame lambda_theta^HX = +1, -1, +0.1) as a function of pT for |y| < 1.2.
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 a Z boson, decaying into two leptons and produced in association with one or more b jets, is studied using proton-proton collisions delivered by the LHC at a centre-of-mass energy of 7 TeV. The data were recorded in 2011 with the CMS detector and correspond to an integrated luminosity of 5 inverse femtobarns. The Z(ll) + b-jets cross sections (where ll = mu mu or ee) are measured separately for a Z boson produced with exactly one b jet and with at least two b jets. In addition, a cross section ratio is extracted for a Z boson produced with at least one b jet, relative to a Z boson produced with at least one jet. The measured cross sections are compared to various theoretical predictions, and the data favour the predictions in the five-flavour scheme, where b quarks are assumed massless. The kinematic properties of the reconstructed particles are compared with the predictions from the MADGRAPH event generator using the PYTHIA parton shower simulation.
The cross section at the particle level for the production of a Z boson with exactly one b-jet.
The cross section at the particle level for the production of a Z boson with at least two b-jets.
The cross section at the particle level for the production of a Z boson with at least one b-jet.
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.
The $\Upsilon$(1S), $\Upsilon$(2S), and $\Upsilon$(3S) production cross sections are measured using a data sample corresponding to an integrated luminosity of 35.8 $\pm$ 1.4 inverse picobarns of proton-proton collisions at $\sqrt{s}$ = 7 TeV, collected with the CMS detector at the LHC. The Upsilon resonances are identified through their decays to dimuons. Integrated over the $\Upsilon$ transverse momentum range $p_{t}^{\Upsilon} \lt$ 50GeV and rapidity range |$y^\Upsilon$| $\lt$ 2.4, and assuming unpolarized Upsilon production, the products of the Upsilon production cross sections and dimuon branching fractions are \begin{equation*}\sigma(pp \to \Upsilon(1S) X) . B(\Upsilon(1S) \to \mu^+ \mu^-) = (8.55 \pm 0.05^{+0.56}_{-0.50} \pm 0.34) nb,\end{equation*} \begin{equation*}\sigma(pp \to \Upsilon(2S) X) . B(\Upsilon(2S) \to \mu^+ \mu^-) = (2.21 \pm 0.03^{+0.16}_{-0.14} \pm 0.09) nb,\end{equation*} \begin{equation*}\sigma(pp \to \Upsilon(3S) X) . B(\Upsilon(3S) \to \mu^+ \mu^-) = (1.11 \pm 0.02^{+0.10}_{-0.08} \pm 0.04) nb, \end{equation*} where the first uncertainty is statistical, the second is systematic, and the third is from the uncertainty in the integrated luminosity. The differential cross sections in bins of transverse momentum and rapidity, and the cross section ratios are presented. Cross section measurements performed within a restricted muon kinematic range and not corrected for acceptance are also provided. These latter measurements are independent of Upsilon polarization assumptions. The results are compared to theoretical predictions and previous measurements.
The fiducial and acceptance-corrected cross sections for PT<50 GeV/c and |rapidity|<2.4.
The fiducial and acceptance corrected UPSI(1S) production cross sections (times di-muon branching ratio) as a function of PT for the |rapidity| range < 2.4. Note these are integrated cross sections and the acceptance-corrected cross sections assume the UPSI(1S) are unpolarized with the variations due to the 4 extreme polarization scenarios shown in the last 4 columns. The fiducial cross sections do not need to make any assumptions on the polarizations scenarios. The luminosity uncertainty of 4% is not included in the systematic errors.
The fiducial and acceptance corrected UPSI(2S) production cross sections (times di-muon branching ratio) as a function of PT for the |rapidity| range < 2.4. Note these are integrated cross sections and the acceptance-corrected cross sections assume the UPSI(2S) are unpolarized with the variations due to the 4 extreme polarization scenarios shown in the last 4 columns. The fiducial cross sections do not need to make any assumptions on the polarizations scenarios. The luminosity uncertainty of 4% is not included in the systematic errors.
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).
A measurement of the J/psi and psi(2S) production cross sections in pp collisions at sqrt(s)=7 TeV with the CMS experiment at the LHC is presented. The data sample corresponds to an integrated luminosity of 37 inverse picobarns. Using a fit to the invariant mass and decay length distributions, production cross sections have been measured separately for prompt and non-prompt charmonium states, as a function of the meson transverse momentum in several rapidity ranges. In addition, cross sections restricted to the acceptance of the CMS detector are given, which are not affected by the polarization of the charmonium states. The ratio of the differential production cross sections of the two states, where systematic uncertainties largely cancel, is also determined. The branching fraction of the inclusive B to psi(2S) X decay is extracted from the ratio of the non-prompt cross sections to be: BR(B to psi(2S) X) = (3.08 +/- 0.12(stat.+syst.) +/- 0.13(theor.) +/- 0.42(BR[PDG])) 10^-3
The (unpolarised) acceptance corrected J/PSI cross section times branching ratio to MU+ MU- for (PROMPT) and NON-PROMPT) production in the |rapidity| bin 0.0-0.9.
The (unpolarised) acceptance corrected J/PSI cross section times branching ratio to MU+ MU- for (PROMPT) and NON-PROMPT) production in the |rapidity| bin 0.9-1.2.
The (unpolarised) acceptance corrected J/PSI cross section times branching ratio to MU+ MU- for (PROMPT) and NON-PROMPT) production in the |rapidity| bin 1.2-1.6.
The Upsilon production cross section in proton-proton collisions at sqrt(s) = 7 TeV is measured using a data sample collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 3.1 +/- 0.3 inverse picobarns. Integrated over the rapidity range |y|<2, we find the product of the Upsilon(1S) production cross section and branching fraction to dimuons to be sigma(pp to Upsilon(1S) X) B(Upsilon(1S) to mu+ mu-) = 7.37 +/- 0.13^{+0.61}_{-0.42}\pm 0.81 nb, where the first uncertainty is statistical, the second is systematic, and the third is associated with the estimation of the integrated luminosity of the data sample. This cross section is obtained assuming unpolarized Upsilon(1S) production. If the Upsilon(1S) production polarization is fully transverse or fully longitudinal the cross section changes by about 20%. We also report the measurement of the Upsilon(1S), Upsilon(2S), and Upsilon(3S) differential cross sections as a function of transverse momentum and rapidity.
Production cross sections integrated over the range |eta| < 2 and PT < 30 GeV. The second systematic error is the uncertainty on the luminosity.
UPSI(1S) differential cross sections for |y| < 2.
UPSI(2S) differential cross sections for |y| < 2.
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.
The observation of an anomalous J/ ψ suppression in Pb–Pb collisions by the NA50 Collaboration can be considered as the most striking indication for the deconfinement of quarks and gluons at SPS energies. In this Letter, we determine the J/ ψ suppression pattern as a function of the forward hadronic energy E ZDC measured in a Zero Degree Calorimeter (ZDC). The direct connection between E ZDC and the geometry of the collision allows us to calculate, within a Glauber approach, the precise relation between the number of participant nucleons N part and E ZDC . Then, we check if the experimental data can be better explained by a sudden or a smooth onset of the anomalous J/ ψ suppression as a function of the number of participants.
Minimum Bias E(C=ZDC) spectrum. Data extracted from fig with g3data, statistical errors not included and are set to 0, the systematic errors given by g3data due to extraction.
Number of participants as a function of E(C=ZDC) Data exctracted from fig with g3data, the systematic errors given by g3data due to extraction, and those marked (stat) are in this case the r.m.s. of the Npart distribution at fixed E(C=ZDC).;.
SIG(J/PSI)/SIG(DY) as a function of E(C=ZDC) with the standard analyses of the 1996 DATA 1996, standard analyses.
The NuTeV experiment at Fermilab has used a sign-selected neutrino beam to perform a search for the lepton number violating process $\bar{\nu}_mu e^- \to \mu^- \bar{\nu}_e$, and to measure the cross-section of the Standard Model inverse muon decay process $\nu_{\mu} e^- \to \mu^- \nu_e$. NuTeV measures the inverse muon decay asymptotic cross-section $\sigma/E$ to be 13.8 $\pm$ 1.2 $\pm$ 1.4 x $10^{-42} cm^2$/GeV. The experiment also observes no evidence for lepton number violation and places one of the most restrictive limits on the LNV/IMD cross-section ratio at $\sigma (\bar{\nu}_{\mu} e^- \to \mu^- \bar{\nu}_e) /\sigma (\nu_{\mu}e^- \to \mu^- \nu_e$) $\le$ 1.7% at 90% C.L. for V-A couplings and $\le$ 0.6% for scalar couplings.
No description provided.
No description provided.
Measurements are presented of the polarisation of W+W- boson pairs produced in e+e- collisions, and of CP-violating WWZ and WWGamma trilinear gauge couplings. The data were recorded by the OPAL experiment at LEP during 1998, where a total integrated luminosity of 183 pb^-1 was obtained at a centre-of-mass energy of 189 GeV. The measurements are performed through a spin density matrix analysis of the W boson decay products. The fraction of W bosons produced with longitudinal polarisation was found to be sigma_L/sigma_total = (21.0 +- 3.3 +- 1.6)% where the first error is statistical and the second systematic. The joint W boson pair production fractions were found to be sigma_TT/sigma_total = (78.1 +- 9.0 +- 3.2) %, sigma_LL/sigma_total = (20.1 +- 7.2 +- 1.8) % and sigma_TL/sigma_total = (1.8 +- 14.7 +- 3.8) %. In the CP-violating trilinear gauge coupling sector we find kappa_z = -0.20 +0.10 -0.07, g^z_4 = -0.02 +0.32 -0.33 and lambda_z = -0.18 +0.24 -0.16, where errors include both statistical and systematic uncertainties. In each case the coupling is determined with all other couplings set to their Standard Model values except those related to the measured coupling via SU(2)_LxU(1)_Y symmetry. These results are consistent with Standard Model expectations.
Individual W-boson transverse polarised cross-sections.
Individual W-boson longitudinal polarised cross-sections.
W pair polarized cross-sections. (C=TT), (C=LL), and (C=TL) stand for both W transversely polarised, for both W longitudinally polarised, and for transversely and longitudinally polarisedW-bosons, respectively.
The analysis of the data collected by the NA50 experiment in 1998, reported in this paper, extends and clarifies the pattern of the previously observed J/ ψ anomalous suppression. This new measurement, besides providing a deeper understanding of the previous observations, reveals a steady significative decrease in the J/ ψ production rate up to the most central Pb-Pb collisions. It clearly rules out the presently available conventional (hadronic) models of J/ ψ suppression, which unanimously predict a saturation of the J/ ψ rate for central Pb-Pb collisions. On the contrary and together with the sharp onset of the anomalous suppression previously reported, the new observation leads to a global production rate pattern which finds its natural explanation in the framework of the formation of a deconfined state of quarks and gluons.
SIG(J/PSI)/SIG(DY) as a function of ET with the standard analyses of 1996. DATA 1996, standard analyses.
SIG(J/PSI)/SIG(DY) as a function of ET with the minium bias analyses of 1996. DATA 1996, MB Analyses.
SIG(J/PSI)/SIG(DY) as a function of E(NAME=TRANSVERSE) with the minium bias analyses of 1998. DATA 1998, MB Analyses.
The production of the J/ ψ and ψ ′ charmonia states has been studied, through their dimuon decay, in proton, Oxygen and Sulphur induced reactions, by the NA38 experiment at the CERN SPS. The proton data was collected with beams of 200 and 450 GeV, while the ion beams had an energy of 200 GeV per incident nucleon. The J/ ψ production cross-section per nucleon-nucleon collision exhibits a remarkably continuous pattern, as a function of the product of the mass numbers of the interacting nuclei, from pp up to S-U reactions. The same pattern is observed within S-U collisions, as a function of the collision centrality. While in p-A interactions both charmonia states exhibit the same A-dependence, in S-U collisions the ψ ′ production is very strongly suppressed.
Results of fitting the 200 and 450 GeV J/PSI data separately with a power law parametrization SIG=SIG0*(A*B)**POWER, where A and B are the beam and targetmass numbers. The value obtained from a combined fit is also given, as well as the ratio between the values of SIG0 for the 200 and 450 GeV data sets.
The J/PSI cross sections per nucleon (times the BR to di-muons) rescaled to 200 GeV/nucleon, using the SIG0 ratio detemined in the previous table, and to the cm rapidity window 0 to 1. The errors are combined statistical and systematic.
The ratio between the PSI(3685) and the J/PSI production cross section, times their BR into di-muons, at an incident beam energy of 450 GeV per nucleon. The errors are combined statistical and systematic.
The cross sections and forward-backward asymmetries of hadronic and leptonic events produced in e+e- collisions at centre-of-mass energies of 130-183 GeV are presented. Results for ee, mumu, tautau, qq, bb and cc production show no significant deviation from the Standard Model predictions. This enable constraints to be set upon physics beyond the Standard Model such as four-fermion contact interactions, leptoquarks, Z' bosons and R-parity violating squarks and sneutrinos. Limits on the energy scale Lambda of eeff contact interactions are typically in the range from 2-10 TeV. Limits on R-parity violating sneutrinos reach masses of a few hundred GeV for large values of their Yukawa couplings.
No description provided.
No description provided.
No description provided.
DO has measured the inclusive production cross section of W and Z bosons in a sample of 13 pb$^{-1}$ of data collected at the Fermilab Tevatron. The cross sections, multiplied by their leptonic branching fractions, for production in pbar-p collisions at sqrt{s}=1.8 TeV are sigma_W*B(W->e nu) = 2.36+-0.02+-0.08+-0.13 nb, sigma_W*B(W->mu nu) = 2.09+-0.06+-0.22+-0.11 nb, sigma_Z*B(Z->e+ e-) = 0.218+-0.008+-0.008+-0.012 nb, and sigma_Z*B(Z->mu+ mu-) = 0.178+-0.022+-0.021+-0.009 nb, where the first uncertainty is statistical and the second systematic; the third reflects the uncertainty in the integrated luminosity. For the combined electron and muon analyses, we find sigma_W*B(W->l mu)/sigma_Z*B(Z->l+ l-) = 10.90+-0.52. Assuming standard model couplings, we use this result to determine the width of the W boson, and obtain Gamma(W) = 2.044+-0.097 GeV.
No description provided.
Combined electron and muon analysis.
The NA50 collaboration has measured J/ψ , ψ′ and Drell Yan pair production in Pb Pb interactions at 158 GeV/ c per nucleon at the CERN SPS. Final results from the 1995 run and preliminary ones from the higher statistics 1996 run are presented. A anomalous J/ψ suppression (relative to the Drell-Yan process) has been observed with respect to the suppression pattern established in experiments NA38 and NA51 with proton, oxygen and sulfur beams. The 1996 data allow a detailed study of the suppression pattern in the Pb Pb sample itself, showing a discontinuity around an E T value (the neutral transverse electromagnetic energy) of 50 GeV. The ψ′ is also suppressed relative to Drell-Yan, with a pattern very similar to the one observed in S U collisions. Finally, the p T distributions of dimuons are presented. The average p T 2 of the J/ψ in Pb Pb collisions does not increase any more with E T above 100 GeV.
ET - neutral transverse energy in the electromagnetic calorimeter, etarap=1.1-2.3.
The Drell-Yan and J ψ cross-sections measured in PbPb collisions are compared with the values extrapolated from the results obtained in proton and light ion induced reactions. While the Drell-Yan production exhibits the normal expected behaviour, the yield of J ψ in PbPb interactions is abnormally low, as it lies 9 standard deviations below the expected value. Moreover, the departure from the expected behaviour increases significantly from peripheral to central collisions.
The results from other experiments are also presented.
Different data are rescaled at 200 GeV.
First results are reported on J ψ and Drell-Yan cross-sections in PbPb reactions at 158 GeV/ c per nucleon. The ratio of cross-sections σ J/ψ /σ DY is studied as a function of the impact parameter of the collision estimated from the measured transverse energy.
No description provided.
No description provided.
The Drell-Yan cross sections are taken in the mass interval 2.9 to 4.5 GeV. SIG/SIG ratio are free from most systematic errors.
In a sample of 3.02 million hadronic Z 0 decays collected by the DELPHI detector, 270 J ψ → ℓ + ℓ − candidates have been selected. A search for fully reconstructed B c ± mesons has yielded one B c ± → J ψ π ± candidate, no B c ± → J ψ ℓ ± ν ℓ candidates, and one B c ± → J ψ , π + π − π ± candidate, consistent with expected background in each channel. The following 90% confidence level upper limits are determined: Br(Z 0 → B c ± X) × Br(B c ± → J ψ π ± ) < (1.05 to 0.84) × 10 −4 and Br(Z 0 → B c ± X) × Br(B c ± → J ψ ℓ ± ν ℓ ) < (5.8 to 5.0) × 10 −5 , where the ranges quoted correspond to the range of predicted B c ± lifetimes from 0.4 to 1.4 ps, and Br(Z 0 → B c ± X) × Br(B c ± → J ψ π + π − π ± ) < 1.75 × 10 −4 , constant over the range of predicted B c ± lifetimes.
B/C life-time equals (0.4 to 1.4) ps.
Limits on $\nu_\mu (\overline{\nu}_\mu) \to \nu_e (\overline{\nu}_e)$ oscillations based on a statistical separation of $\nu_e N$ charged current interactions in the CCFR detector at Fermilab are presented. $\nu_e$ interactions are identified by the difference in the longitudinal shower energy deposition pattern of $\nu_e N \rightarrow eX$ versus $\nu_\mu N \to \nu_\mu X$ interactions. Neutrino energies range from 30 to 600 GeV with a mean of 140 GeV, and $\nu_\mu$ flight lengths vary from 0.9 km to 1.4 km. The lowest 90% confidence upper limit in $sin^2 2\alpha$ of $1.1 \times 10^{-3}$ is obtained at $\Delta m^2 \sim 300 eV^2$. For $sin^2 2\alpha = 1$, $\Delta m^2 > 1.6 eV^2$ is excluded, and for $\Delta m^2 \gg 1000 eV^2$, $sin^2 2\alpha > 1.8 \times 10^{-3}$ is excluded. This result is the most stringent limit to date for $\Delta m^2 > 25 eV^2$ and it excludes the high $\Delta m^2$ oscillation region favoured by the LSND experiment. The $\nu_\mu$-to-$\nu_e$ cross-section ratio was measured as a test of $\nu_\mu (\bar\nu_\mu) \leftrightarrow \nu_e (\bar\nu_e)$ universality to be $1.026 \pm 0.055$.
ALPHA is the neutrino mixing angle. The result for SIN(ALPHA)**2 from the fit at each Delta(M)**2 for NUMU -->NUE oscillations. The 90% CL upper limit is equal to the best fit SIN(ALPHA)**2 + 1.2*SIGMA.
No description provided.
We report on the analysis of Charmonium and Bottomium states produced in p-Si interactions at s =38.7 GeV . The data have been collected with the open geometry spectrometer of the E771 Experiment at the FNAL High Intensity Lab. J ψ , ψ′ and γ total cross sections as well as the ratio B(ψ′ → μμ)σ(ψ′) (B( J ψ → μμ)σ( J ψ )) have been measured. Results are compared with theoretical predictions and with results at other energies.
The total inclusive cross section per nucleon has been evaluated assuming an atomic weight dependence of A**POWER with POWER = 0.920 +- 0.008.
combined UPSI(1S) and UPSI(2S) cross section.
No description provided.
We report on measurements of the ϒ(1S), ϒ(2S), and ϒ(3S) differential, (d2σdPtdy)y=0, and integrated cross sections in pp¯ collisions at s=1.8 TeV using a sample of 16.6 ± 0.6 pb−1 collected by the Collider Detector at Fermilab. The three resonances were reconstructed through the decay ϒ→μ+μ−. Comparison is made to a leading order QCD prediction.
SIG*Br(UPSI --> MU+ MU-).
SIG*Br(UPSI --> MU+ MU-).
SIG*Br(UPSI --> MU+ MU-).
A sample of 25000 Z 0 → τ + τ − events collected by the DELPHI experiment at LEP in 1991 and 1992 is used to measure the leptonic branching fractions of the τ lepton. The results are B(τ → eν ν ) = (17.51 ± 0.39) % and B(τ → μν ν ) = (17.02 ± 0.31) %. The ratio of the muon and electron couplings to the weak charged current is measured to be g μ g e = 1.000 ± 0.013 , satisfying e-μ universality. The leptonic branching fraction corrected to the value for a massless lepton, assuming e-μ universality, is found to be B(τ → lν ν ) = (17.50 ± 0.25) %.
Axis error includes +- 0.23/0.23 contribution (Data statistics).
Axis error includes +- 0.19/0.19 contribution (Data statistics).
Combined from the two branching fractions above. E-MU universality assumed.
We have searched for the decay D 0 → μ + μ − among 1.25 × 10 5 μ + μ − pairs produced by 350 GeV/ c π − particles interacting in copper and tungsten targets. Using a high-resolution silicon-microstrip detector followed by a large-acceptance magnetic spectrometer and a muon filter we are able to discriminate between prompt and non-prompt muons and to measure dimuon masses. No candidate compatible with a D 0 → μ + μ − decay has been found, allowing us to set an upper limit on the branching fraction B( D 0 → μ + μ − ) of 7.6 × 10 −6 at the 90% confidence level.
NUCLEUS OF TARGET=CU+WT.
J ψ and ψ′ production cross sections are studied for several proton induced reactions and in SU collisions, in the NA38 experiment, by measuring the resonances' decays in the muon pair channel. Whereas in p-A interactions the ψ ′/ J / ψ ratio remains constantin going from p-p and p-d collisions to p-W and p-U, with a mean value of 1.76% ± 0.04%, in the SU data it exhibits half of this value and decreases as centrality of the collision increases. Also studied are the differences between the γ π 0 ratio yields correlated with the J ψ mass range and other dimuon masses; no significant effect is seen.
DATA IN THE COLLINS-SOPPER FRAME, OF -0.5<COS(THETA)<0.5.
DATA IN THE COLLINS-SOPPER FRAME, OF -0.5<COS(THETA)<0.5.
No description provided.
In this paper we present a study on the production of the J ψ and ψ′ resonances, decaying into muon pairs, in S-U collisions, at 200 GeV per incident nucleon. We find that the ratio between ψ′ and tJ ψ yields decreases as E T , the neutral transverse energy produced in the collision, increases. There is also a clear decrease of this ratio when going from p-W to S-U interactions. Assuming the high mass continuum to be Drell-Yan we discuss the possible understanding of the intermediate dimuon mass region as a superposition of Drell-Yan (extrapolated down in mass) and muon pairs from the semileptonic decays of charmed mesons. The p-W data is found to be explained by this procedure. However, the S-U data seems to be incompatible with a linear extrapolation from the proton-nucleus results.
THE NEUTRAL TRANSVERSE ENERGY PRODUCED IN THE COLLISION > 15 GEV.
THE NEUTRAL TRANSVERSE ENERGY PRODUCED IN THE COLLISION > 15 GEV.
THE NEUTRAL TRANSVERSE ENERGY PRODUCED IN THE COLLISION > 15 GEV.
The x and Q 2 dependence of the single photon exchange cross section d 2 σ /d Q 2 d x and the proton structure functions F 2 ( x , Q 2 ) and R ( x , Q 2 ) have been measured in deep inelastic muon proton scattering in the region 0.02 < x < 0.8 and 3 < Q 2 < 190 GeV 2 . By comparing data at different incident muon energies R was found to have little kinematic dependence and an average value of −0.010 ± 0.037 (stat.) ± 0.102 (stat.). The observed deviations from scaling gave the value of Λ MS , the QCD mass scale parameter, to be 105 −45 +55 (stat.) −45 +85 (syst.) MeV. The fraction of the momentum of the nucleon carried by gluons was found to be ∼56% at Q 2 ∼22.5 GeV 2 . It is shown that to obtain a description of the data for F 2 ( x , Q 2 ) together with that measured in deep inelastic electron-proton scattering at lower Q 2 it is necessary to include additional higher twist contributions. The value of Λ MS remains unchanged with the inclusion of these contributions which were found to have an x -dependence of the form x 3 /(1 − x ).
No description provided.
No description provided.
No description provided.
The fragmentation of the hadronic system into Λ, Σ(1385), K ) and K ∗ (892) in deep-inelastic charged-current interactions of high energy neutrinos and antineutrinos with proton and neutron is analyzed. The results obtained for the production of these particles from the various initial states are compared with each other and with the predictions of the Lund fragmentation model. This comparison shows that a spectator diquark does not fragment as a whole in a fraction of the interactions. The role of the sea quarks in the baryon formation process is underlined. Strange vector and pseudoscalar mesons are likely to be produced at similar rates.
No description provided.
SIG(C=LAMBDA) denotes the inclusive LAMBDA production in the same reaction.
SIG(C=KS) denotes the inclusive KS production in the same reaction.
Light ion collisions with carbon target at 4.2 GeV/c/N are studied. Pion multiplicity distributions, momentum and angular spectra are analysed. These data are described in terms of models assuming independent interactions of nucleons from the projectile nucleus with the target.
No description provided.
No description provided.
No description provided.
We have measured the reactions e + e − → e + e − → μ + μ − and e + e − → γγ at c.m. energies between 12 and 31.6 GeV. Excellent agreement with the predictions of QED has been found, resulting in cut off parameters Λ + > 112 GeV and Λ − > 139 GeV for the first process and Λ + > 34 GeV and Λ − > 42 GeV (95% c.1.) for the last one. A limit on the Weinberg angle of sin 2 θ W < 0.55 (95% c.1.) has been obtained.
SIG(C=QED) QED predictions for the cross sections. Only statistical errors are given.
SIG(C=QED) QED predictions for the cross sections. Only statistical errors are given.
SIG(C=QED) QED predictions for the cross sections. Only statistical errors are given.
We have observed 217 (66) events of the process νp→νp (ν¯p→ν¯p) with an estimated background of 82 (28). The neutral-to-charged-current ratios are σ(νp→νp)σ(νn→μ−p)=0.11±0.02 and σ(ν¯p→ν¯p)σ(ν¯p→μ+n)=0.19±0.05 for 0.40<Q2<0.90 (GeV/c)2, where -Q2 is the square of the momentum transfer to the nucleon. These yield σ(ν¯p→ν¯p)σ(νp→νp)=0.53±0.17. The neutral-current form factors at Q2=0 are GE=0.5−0.5+0.25, GM=1.0−0.04+0.35, and gA=0.5−0.15+0.2.
No description provided.
The cross section ratio of the elastic neutral current reaction ν p→ ν p to the quasi-elastic charged current reaction ν n→ μ − p has been measured in the kinematical region 0.3⩽ q 2 ⩽1.0 (GeV/ c ) 2 . The measured value is R M =0.17±0.08. Model dependent corrections are applied, especially for ν n→ ν n contamination, and the result is compared to various models.
(C=OBSERVED) and (C=CORRECTED) are the observed and corrected for the nuclear effects ratios.
Relative rates for deep inelastic neutrino and antineutrino scattering without a finalstate muon have been measured. For neutrinos the result is Rν=σ(νμ+nucleon→νμ+hadrons)σ(νμ+nucleon→μ−+hadrons)=0.11±0.05. The corresponding ratio for antineutrinos is Rν¯=0.32±0.09.
No description provided.
We report here additional positive results of a search for muonless neutrino- and anti-neutrino-induced events using an enriched antineutrino beam and a muon identifier of relatively high geometric detection efficiency. The ratio of muonless to muon event rates is observed to be R=0.20±0.05. We observe no background derived from ordinary neutrino or antineutrino interactions that is capable of explaining the muonless signal.
No description provided.
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