A data sample of about 3.0 million hadronic Z decays collected by the ALEPH experiment at LEP in ... more A data sample of about 3.0 million hadronic Z decays collected by the ALEPH experiment at LEP in the years 1991 through 1994, is used to make an inclusive selection of B hadron events. In this event sample 4227140252 B mesons in the decay B ! Band 1944108161 B mesons decaying into a B meson and a c harged pion are reconstructed. For the well established B meson the following quantities are obtained: M = M B M B = (45:30 0:35 0:87) MeV=c 2 and N B =(N B + N B ) = (77:1 2:6 7:0)%. The angular distribution of the photons in the B rest frame is used to measure the relative contribution of longitudinal B polarization states to be L =( L + T ) = (33 6 5)%. Resonance structure in the M(B) M(B) mass dierence is observed at (424410) MeV=c 2 . Its shape and position is in agreement with the expectation for B u;d states decaying into B () u;d .
Data on the inclusive production of the neutral vector mesons 0 (770), !(782), K 0 (892), and (10... more Data on the inclusive production of the neutral vector mesons 0 (770), !(782), K 0 (892), and (1020) in hadronic Z decays recorded with the ALEPH detector at LEP are presented and compared to Monte Carlo model predictions. Bose-Einstein eects are found to be important in extracting a reliable value for the 0 production rate. An average 0 multiplicity o f 1 : 45 0:21 per event is obtained. The ! is detected via its three pion decay m o d e ! ! + 0 and has a total rate of 1:07 0:14 per event. The multiplicity of the K 0 is 0:83 0:09, whilst that of the is 0:122 0:009, both measured using their charged decay modes. The measurements provide information on the relative production rates of vector and pseudoscalar mesons, as well as on the relative probabilities for the production of hadrons containing u, d, and s quarks. In the following, a specic isospin state implies the inclusion of the antiparticle as well.
Measurement of σ(e + e − → π + π − γ) and extraction of σ(e + e − → π + π − ) below 1 GeV with th... more Measurement of σ(e + e − → π + π − γ) and extraction of σ(e + e − → π + π − ) below 1 GeV with the KLOE detector
√ s = 7 TeV measured with the ATLAS detector ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t... more √ s = 7 TeV measured with the ATLAS detector ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t r a c t Dijet angular distributions from the first LHC pp collisions at center-of-mass energy √ s = 7 TeV have been measured with the ATLAS detector. The dataset used for this analysis represents an integrated luminosity of 3.1 pb −1 . Dijet χ distributions and centrality ratios have been measured up to dijet masses of 2.8 TeV, and found to be in good agreement with Standard Model predictions. Analysis of the χ distributions excludes quark contact interactions with a compositeness scale Λ below 3.4 TeV, at 95% confidence level, significantly exceeding previous limits. √ s = 7 TeV at the LHC. The data sample represents an integrated luminosity of 3.1 pb −1 , recorded in periods of stable collisions, through August 2010. The two distributions under
The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge... more The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge bosons (W′), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 1.04 fb− 1. No excess above Standard Model expectations is observed. AW′ with Sequential Standard Model couplings is excluded at the 95% confidence level for masses up to 2.15 TeV.
Using the ATLAS detector, a centrality-dependent suppression has been observed in the yield of J/... more Using the ATLAS detector, a centrality-dependent suppression has been observed in the yield of J/ψ mesons produced in the collisions of lead ions at the Large Hadron Collider. In a sample of minimum-bias lead-lead collisions at a nucleon-nucleon centre of mass energy √ s N N = 2.76 TeV, corresponding to an integrated luminosity of about 6.7 µb −1 , J/ψ mesons are reconstructed via their decays to µ + µ − pairs. The measured J/ψ yield, normalized to the number of binary nucleon-nucleon collisions, is found to significantly decrease from peripheral to central collisions. The centrality dependence is found to be qualitatively similar to the trends observed at previous, lower energy experiments. The same sample is used to reconstruct Z bosons in the µ + µ − final state, and a total of 38 candidates are selected in the mass window of 66 to 116 GeV. The relative Z yields as a function of centrality are also presented, although no conclusion can be inferred about their scaling with the number of binary collisions, because of limited statistics. This analysis provides the first results on J/ψ and Z production in lead-lead collisions at the LHC.
Physical Review D - Particles, Fields, Gravitation and Cosmology, 2012
A search for supersymmetry in the context of general gauge-mediated (GGM) breaking with the light... more A search for supersymmetry in the context of general gauge-mediated (GGM) breaking with the lightest neutralino as the next-to-lightest supersymmetric particle and the gravitino as the lightest is presented. The data sample corresponds to an integrated luminosity of 36 pb −1 recorded by the CMS experiment at the LHC. The search is performed using events containing two or more isolated photons, at least one hadronic jet, and significant missing transverse energy. No excess of events at high missing transverse energy is observed. Upper limits on the signal cross section for GGM supersymmetry between 0.3 and 1.1 pb at the 95% confidence level are determined for a range of squark, gluino, and neutralino masses, excluding supersymmetry parameter space that was inaccessible to previous experiments.
A search for the weak production of charginos and neutralinos decaying to a final state with thre... more A search for the weak production of charginos and neutralinos decaying to a final state with three leptons (electrons or muons) and missing transverse momentum is presented. The analysis uses 2:06 fb À1 of ffiffi ffi s p ¼ 7 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with standard model expectations in two signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric and simplified models. For the simplified models, degenerate lightest chargino and next-to-lightest neutralino masses up to 300 GeV are excluded for mass differences from the lightest neutralino up to 300 GeV.
The results of a search for pair production of the lighter scalar partners of top quarks (t˜ 1) i... more The results of a search for pair production of the lighter scalar partners of top quarks (t˜ 1) in 2.05 fb− 1 of pp collisions at s= 7 TeV using the ATLAS experiment at the LHC are reported. Scalar top quarks are searched for in events with two same flavour opposite-sign leptons (e, μ) with invariant mass consistent with the Z boson mass, large missing transverse momentum and jets in the final state. At least one of the jets is identified as originating from a b-quark. No excess over Standard Model expectations is found. The results are ...
Search for new particles decaying to ZZ using final states with leptons and jets with the ATLAS d... more Search for new particles decaying to ZZ using final states with leptons and jets with the ATLAS detector in √ s = 7 TeV proton-proton collisions Abstract A search is presented for a narrow resonance decaying to a pair of Z bosons using data corresponding to 1.02 fb −1 of integrated luminosity collected by the ATLAS experiment from pp collisions at √ s = 7 TeV. Events containing either four charged leptons ( ) or two charged leptons and two jets ( jj) are analyzed and found to be consistent with the Standard Model background expectation. Lower limits on a resonance mass are set using the Randall-Sundrum (RS1) graviton model as a benchmark. Using both and jj events, an RS1 graviton with k/m pl = 0.1 and mass between 325 and 845 GeV is excluded at 95% confidence level. In addition, the events are used to set a modelindependent fiducial cross section limit of σ fid (pp → X → ZZ) < 0.92 pb at 95% confidence level for any new sources of ZZ production with m ZZ greater than 300 GeV. arXiv:1203.0718v2 [hep-ex] 25 May 2012 1 ATLAS uses a right-handed coordinate system with its origin at the nominal interaction point (IP) in the center of the detector and the z-axis along the beam line. The x-axis points from the IP to the center of the LHC ring, and the y axis points upward. Cylindrical coordinates (R, φ) are used in the transverse plane, φ being the azimuthal angle around the beam line. The pseudorapidity is defined in terms of the polar angle θ (z = r cos θ) as η = − ln tan(θ/2). The transverse energy E T is defined as E sin θ, where E is the energy associated to the calorimeter cell or energy cluster. Similarly, p T is the momentum component transverse to the beam line. 61
A search is presented for the pair production of light scalar top quarks in sqrt (s)= 7 TeV proto... more A search is presented for the pair production of light scalar top quarks in sqrt (s)= 7 TeV proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider. This analysis uses the full data sample collected during 2011 that corresponds to a total integrated luminosity of 4.7 fb-1. Light scalar top quarks are searched for in events with two opposite-sign leptons (e, mu), large missing transverse momentum and at least one jet in the final state. No excess over Standard Model expectations is found, and the results are ...
We present the results of a search for new, heavy particles that decay at a significant distance ... more We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb −1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.
This Letter presents a search for contact interactions in the dielectron and dimuon channels usin... more This Letter presents a search for contact interactions in the dielectron and dimuon channels using data from proton–proton collisions produced by the LHC at s= 7 TeV and recorded by the ATLAS detector. The data sample, collected in 2011, corresponds to an integrated luminosity of 1.08 and 1.21 fb− 1 in the e+ e− and μ+ μ− channels, respectively. No significant deviations from the standard model are observed. Using a Bayesian approach with a prior flat in 1/Λ2, the following 95% CL lower limits are placed on the energy scale ...
Proton-proton collisions at √ s = 7 TeV and heavy ion collisions at √ s NN = 2.76 TeV were produc... more Proton-proton collisions at √ s = 7 TeV and heavy ion collisions at √ s NN = 2.76 TeV were produced by the LHC and recorded using the ATLAS experiment's trigger system in 2010. The LHC is designed with a maximum bunch crossing rate of 40 MHz and the ATLAS trigger system is designed to record approximately 200 of these per second. The trigger system selects events by rapidly identifying signatures of muon, electron, photon, tau lepton, jet, and B meson candidates, as well as using global event signatures, such as missing transverse energy. An overview of the ATLAS trigger system, the evolution of the system during 2010 and the performance of the trigger system components and selections based on the 2010 collision data are shown. A brief outline of plans for the trigger system in 2011 is presented.
Measurements of the electron and muon inclusive cross-sections in proton-proton collisions at √ s... more Measurements of the electron and muon inclusive cross-sections in proton-proton collisions at √ s = 7 TeV with the ATLAS detector ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t r a c t
Measurement of the W W cross section in √ s = 7 TeV pp collisions with the ATLAS detector and lim... more Measurement of the W W cross section in √ s = 7 TeV pp collisions with the ATLAS detector and limits on anomalous gauge couplings ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t r a c t This Letter reports a measurement of the W W production cross section in √ s = 7 TeV pp collisions using data corresponding to an integrated luminosity of 1.02 fb −1 collected with the ATLAS detector. Using leptonic decays of oppositely charged W bosons, the total measured cross section is σ (pp → W W ) = 54.4 ± 4.0 (stat.) ± 3.9 (syst.) ± 2.0 (lumi.) pb, consistent with the Standard Model prediction of σ (pp → W W ) = 44.4 ± 2.8 pb. Limits on anomalous electroweak triple-gauge couplings are extracted from a fit to the transverse-momentum distribution of the leading charged lepton in the event.
A measurement of the production cross-section for top quark pairs (tt) in pp collisions at √ s = ... more A measurement of the production cross-section for top quark pairs (tt) in pp collisions at √ s = 7 TeV is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in two different topologies: single lepton (electron e or muon μ) with large missing transverse energy and at least four jets, and dilepton (ee, μμ or eμ) with large missing transverse energy and at least two jets. In a data sample of 2.9 pb −1 , 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding expected backgrounds from non-tt Standard Model processes are estimated using data-driven methods and determined to be 12.2 ± 3.9 events and 2.5 ± 0.6 events, respectively. The kinematic properties of the selected events are consistent with SM tt production. The inclusive top quark pair production cross-section is measured to be σ tt = 145 ± 31(stat.) +42 −27 (syst.) pb.
A data sample of about 3.0 million hadronic Z decays collected by the ALEPH experiment at LEP in ... more A data sample of about 3.0 million hadronic Z decays collected by the ALEPH experiment at LEP in the years 1991 through 1994, is used to make an inclusive selection of B hadron events. In this event sample 4227140252 B mesons in the decay B ! Band 1944108161 B mesons decaying into a B meson and a c harged pion are reconstructed. For the well established B meson the following quantities are obtained: M = M B M B = (45:30 0:35 0:87) MeV=c 2 and N B =(N B + N B ) = (77:1 2:6 7:0)%. The angular distribution of the photons in the B rest frame is used to measure the relative contribution of longitudinal B polarization states to be L =( L + T ) = (33 6 5)%. Resonance structure in the M(B) M(B) mass dierence is observed at (424410) MeV=c 2 . Its shape and position is in agreement with the expectation for B u;d states decaying into B () u;d .
Data on the inclusive production of the neutral vector mesons 0 (770), !(782), K 0 (892), and (10... more Data on the inclusive production of the neutral vector mesons 0 (770), !(782), K 0 (892), and (1020) in hadronic Z decays recorded with the ALEPH detector at LEP are presented and compared to Monte Carlo model predictions. Bose-Einstein eects are found to be important in extracting a reliable value for the 0 production rate. An average 0 multiplicity o f 1 : 45 0:21 per event is obtained. The ! is detected via its three pion decay m o d e ! ! + 0 and has a total rate of 1:07 0:14 per event. The multiplicity of the K 0 is 0:83 0:09, whilst that of the is 0:122 0:009, both measured using their charged decay modes. The measurements provide information on the relative production rates of vector and pseudoscalar mesons, as well as on the relative probabilities for the production of hadrons containing u, d, and s quarks. In the following, a specic isospin state implies the inclusion of the antiparticle as well.
Measurement of σ(e + e − → π + π − γ) and extraction of σ(e + e − → π + π − ) below 1 GeV with th... more Measurement of σ(e + e − → π + π − γ) and extraction of σ(e + e − → π + π − ) below 1 GeV with the KLOE detector
√ s = 7 TeV measured with the ATLAS detector ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t... more √ s = 7 TeV measured with the ATLAS detector ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t r a c t Dijet angular distributions from the first LHC pp collisions at center-of-mass energy √ s = 7 TeV have been measured with the ATLAS detector. The dataset used for this analysis represents an integrated luminosity of 3.1 pb −1 . Dijet χ distributions and centrality ratios have been measured up to dijet masses of 2.8 TeV, and found to be in good agreement with Standard Model predictions. Analysis of the χ distributions excludes quark contact interactions with a compositeness scale Λ below 3.4 TeV, at 95% confidence level, significantly exceeding previous limits. √ s = 7 TeV at the LHC. The data sample represents an integrated luminosity of 3.1 pb −1 , recorded in periods of stable collisions, through August 2010. The two distributions under
The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge... more The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge bosons (W′), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 1.04 fb− 1. No excess above Standard Model expectations is observed. AW′ with Sequential Standard Model couplings is excluded at the 95% confidence level for masses up to 2.15 TeV.
Using the ATLAS detector, a centrality-dependent suppression has been observed in the yield of J/... more Using the ATLAS detector, a centrality-dependent suppression has been observed in the yield of J/ψ mesons produced in the collisions of lead ions at the Large Hadron Collider. In a sample of minimum-bias lead-lead collisions at a nucleon-nucleon centre of mass energy √ s N N = 2.76 TeV, corresponding to an integrated luminosity of about 6.7 µb −1 , J/ψ mesons are reconstructed via their decays to µ + µ − pairs. The measured J/ψ yield, normalized to the number of binary nucleon-nucleon collisions, is found to significantly decrease from peripheral to central collisions. The centrality dependence is found to be qualitatively similar to the trends observed at previous, lower energy experiments. The same sample is used to reconstruct Z bosons in the µ + µ − final state, and a total of 38 candidates are selected in the mass window of 66 to 116 GeV. The relative Z yields as a function of centrality are also presented, although no conclusion can be inferred about their scaling with the number of binary collisions, because of limited statistics. This analysis provides the first results on J/ψ and Z production in lead-lead collisions at the LHC.
Physical Review D - Particles, Fields, Gravitation and Cosmology, 2012
A search for supersymmetry in the context of general gauge-mediated (GGM) breaking with the light... more A search for supersymmetry in the context of general gauge-mediated (GGM) breaking with the lightest neutralino as the next-to-lightest supersymmetric particle and the gravitino as the lightest is presented. The data sample corresponds to an integrated luminosity of 36 pb −1 recorded by the CMS experiment at the LHC. The search is performed using events containing two or more isolated photons, at least one hadronic jet, and significant missing transverse energy. No excess of events at high missing transverse energy is observed. Upper limits on the signal cross section for GGM supersymmetry between 0.3 and 1.1 pb at the 95% confidence level are determined for a range of squark, gluino, and neutralino masses, excluding supersymmetry parameter space that was inaccessible to previous experiments.
A search for the weak production of charginos and neutralinos decaying to a final state with thre... more A search for the weak production of charginos and neutralinos decaying to a final state with three leptons (electrons or muons) and missing transverse momentum is presented. The analysis uses 2:06 fb À1 of ffiffi ffi s p ¼ 7 TeV proton-proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with standard model expectations in two signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric and simplified models. For the simplified models, degenerate lightest chargino and next-to-lightest neutralino masses up to 300 GeV are excluded for mass differences from the lightest neutralino up to 300 GeV.
The results of a search for pair production of the lighter scalar partners of top quarks (t˜ 1) i... more The results of a search for pair production of the lighter scalar partners of top quarks (t˜ 1) in 2.05 fb− 1 of pp collisions at s= 7 TeV using the ATLAS experiment at the LHC are reported. Scalar top quarks are searched for in events with two same flavour opposite-sign leptons (e, μ) with invariant mass consistent with the Z boson mass, large missing transverse momentum and jets in the final state. At least one of the jets is identified as originating from a b-quark. No excess over Standard Model expectations is found. The results are ...
Search for new particles decaying to ZZ using final states with leptons and jets with the ATLAS d... more Search for new particles decaying to ZZ using final states with leptons and jets with the ATLAS detector in √ s = 7 TeV proton-proton collisions Abstract A search is presented for a narrow resonance decaying to a pair of Z bosons using data corresponding to 1.02 fb −1 of integrated luminosity collected by the ATLAS experiment from pp collisions at √ s = 7 TeV. Events containing either four charged leptons ( ) or two charged leptons and two jets ( jj) are analyzed and found to be consistent with the Standard Model background expectation. Lower limits on a resonance mass are set using the Randall-Sundrum (RS1) graviton model as a benchmark. Using both and jj events, an RS1 graviton with k/m pl = 0.1 and mass between 325 and 845 GeV is excluded at 95% confidence level. In addition, the events are used to set a modelindependent fiducial cross section limit of σ fid (pp → X → ZZ) < 0.92 pb at 95% confidence level for any new sources of ZZ production with m ZZ greater than 300 GeV. arXiv:1203.0718v2 [hep-ex] 25 May 2012 1 ATLAS uses a right-handed coordinate system with its origin at the nominal interaction point (IP) in the center of the detector and the z-axis along the beam line. The x-axis points from the IP to the center of the LHC ring, and the y axis points upward. Cylindrical coordinates (R, φ) are used in the transverse plane, φ being the azimuthal angle around the beam line. The pseudorapidity is defined in terms of the polar angle θ (z = r cos θ) as η = − ln tan(θ/2). The transverse energy E T is defined as E sin θ, where E is the energy associated to the calorimeter cell or energy cluster. Similarly, p T is the momentum component transverse to the beam line. 61
A search is presented for the pair production of light scalar top quarks in sqrt (s)= 7 TeV proto... more A search is presented for the pair production of light scalar top quarks in sqrt (s)= 7 TeV proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider. This analysis uses the full data sample collected during 2011 that corresponds to a total integrated luminosity of 4.7 fb-1. Light scalar top quarks are searched for in events with two opposite-sign leptons (e, mu), large missing transverse momentum and at least one jet in the final state. No excess over Standard Model expectations is found, and the results are ...
We present the results of a search for new, heavy particles that decay at a significant distance ... more We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb −1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.
This Letter presents a search for contact interactions in the dielectron and dimuon channels usin... more This Letter presents a search for contact interactions in the dielectron and dimuon channels using data from proton–proton collisions produced by the LHC at s= 7 TeV and recorded by the ATLAS detector. The data sample, collected in 2011, corresponds to an integrated luminosity of 1.08 and 1.21 fb− 1 in the e+ e− and μ+ μ− channels, respectively. No significant deviations from the standard model are observed. Using a Bayesian approach with a prior flat in 1/Λ2, the following 95% CL lower limits are placed on the energy scale ...
Proton-proton collisions at √ s = 7 TeV and heavy ion collisions at √ s NN = 2.76 TeV were produc... more Proton-proton collisions at √ s = 7 TeV and heavy ion collisions at √ s NN = 2.76 TeV were produced by the LHC and recorded using the ATLAS experiment's trigger system in 2010. The LHC is designed with a maximum bunch crossing rate of 40 MHz and the ATLAS trigger system is designed to record approximately 200 of these per second. The trigger system selects events by rapidly identifying signatures of muon, electron, photon, tau lepton, jet, and B meson candidates, as well as using global event signatures, such as missing transverse energy. An overview of the ATLAS trigger system, the evolution of the system during 2010 and the performance of the trigger system components and selections based on the 2010 collision data are shown. A brief outline of plans for the trigger system in 2011 is presented.
Measurements of the electron and muon inclusive cross-sections in proton-proton collisions at √ s... more Measurements of the electron and muon inclusive cross-sections in proton-proton collisions at √ s = 7 TeV with the ATLAS detector ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t r a c t
Measurement of the W W cross section in √ s = 7 TeV pp collisions with the ATLAS detector and lim... more Measurement of the W W cross section in √ s = 7 TeV pp collisions with the ATLAS detector and limits on anomalous gauge couplings ✩ .ATLAS Collaboration a r t i c l e i n f o a b s t r a c t This Letter reports a measurement of the W W production cross section in √ s = 7 TeV pp collisions using data corresponding to an integrated luminosity of 1.02 fb −1 collected with the ATLAS detector. Using leptonic decays of oppositely charged W bosons, the total measured cross section is σ (pp → W W ) = 54.4 ± 4.0 (stat.) ± 3.9 (syst.) ± 2.0 (lumi.) pb, consistent with the Standard Model prediction of σ (pp → W W ) = 44.4 ± 2.8 pb. Limits on anomalous electroweak triple-gauge couplings are extracted from a fit to the transverse-momentum distribution of the leading charged lepton in the event.
A measurement of the production cross-section for top quark pairs (tt) in pp collisions at √ s = ... more A measurement of the production cross-section for top quark pairs (tt) in pp collisions at √ s = 7 TeV is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in two different topologies: single lepton (electron e or muon μ) with large missing transverse energy and at least four jets, and dilepton (ee, μμ or eμ) with large missing transverse energy and at least two jets. In a data sample of 2.9 pb −1 , 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding expected backgrounds from non-tt Standard Model processes are estimated using data-driven methods and determined to be 12.2 ± 3.9 events and 2.5 ± 0.6 events, respectively. The kinematic properties of the selected events are consistent with SM tt production. The inclusive top quark pair production cross-section is measured to be σ tt = 145 ± 31(stat.) +42 −27 (syst.) pb.
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Papers by A. Farilla