ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Measurement of the inclusive W-+/- and Z/gamma* cross sections in the e and μdecay channels in pp collisions at root s=7 TeV with the ATLAS detector. Phys. Rev. D, 85(7), 072004–39pp.
Abstract: The production cross sections of the inclusive Drell-Yan processes W-+/- -> l nu and Z/gamma* -> ll (l = e, mu) are measured in proton-proton collisions at root s = 7 TeV with the ATLAS detector. The cross sections are reported integrated over a fiducial kinematic range, extrapolated to the full range, and also evaluated differentially as a function of the W decay lepton pseudorapidity and the Z boson rapidity, respectively. Based on an integrated luminosity of about 35 pb(-1) collected in 2010, the precision of these measurements reaches a few percent. The integrated and the differential W-+/- and Z/gamma* cross sections in the e and μchannels are combined, and compared with perturbative QCD calculations, based on a number of different parton distribution sets available at next-to-next-to-leading order.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Search for resonant WZ production in the WZ -> lvl ' l ' channel in root(s)=7 TeV pp collisions with the ATLAS detector. Phys. Rev. D, 85(11), 112012–21pp.
Abstract: A generic search is presented for a heavy particle decaying to WZ -> lvl'l' (l, l' = e, mu) final states. The data were recorded by the ATLAS detector in root s = 7 TeV pp collisions at the Large Hadron Collider and correspond to an integrated luminosity of 1.02 fb(-1). The transverse mass distribution of the selected WZ candidates is found to be consistent with the standard model expectation. Upper limits on the production cross section times branching ratio are derived using two benchmark models predicting a heavy particle decaying to a WZ pair.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Search for supersymmetry in pp collisions at root s=7 Te V in final states with missing transverse momentum and b-jets with the ATLAS detector. Phys. Rev. D, 85(11), 112006–29pp.
Abstract: The results of a search for supersymmetry in events with large missing transverse momentum and heavy-flavor jets using an integrated luminosity corresponding to 2.05 fb(-1) of pp collisions at root s = 7 TeV recorded with the ATLAS detector at the Large Hadron Collider are reported. No significant excess is observed with respect to the prediction for standard model processes. Results are interpreted in a variety of R-parity conserving models in which scalar bottoms and tops are the only scalar quarks to appear in the gluino decay cascade, and in an SO(10) model framework. Gluino masses up to 600-900 GeV are excluded, depending on the model considered.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Measurement of the production cross section of an isolated photon associated with jets in proton-proton collisions at root s=7 TeV with the ATLAS detector. Phys. Rev. D, 85(9), 092014–30pp.
Abstract: A measurement of the cross section for the production of an isolated photon in association with jets in proton-proton collisions at a center-of-mass energy root s = 7 TeV is presented. Photons are reconstructed in the pseudorapidity range vertical bar eta(gamma)vertical bar < 1.37 and with a transverse energy E-T(gamma) > 25 GeV. Jets are reconstructed in the rapidity range vertical bar y(jet)vertical bar < 4.4 and with a transverse momentum p(T)(jet) > 20 GeV. The differential cross section d sigma/dE(T)(gamma) is measured, as a function of the photon transverse energy, for three different rapidity ranges of the leading-p(T) jet: vertical bar y(jet)vertical bar < 1.2, 1.2 <= vertical bar y(jet)vertical bar < 2.8 and 2.8 <= vertical bar y(jet)vertical bar < 4.4. For each rapidity configuration the same-sign (eta(gamma)y(jet) >= 0) and opposite-sign (eta(gamma) y(jet) < 0) cases are studied separately. The results are based on an integrated luminosity of 37 pb(-1), collected with the ATLAS detector at the LHC. Next-to-leading order perturbative QCD calculations are found to be in fair agreement with the data, except for E-T(gamma) <= 45 GeV, where the theoretical predictions overestimate the measured cross sections.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2011). Search for contact interactions in dimuon events from pp collisions at sqrt(s)=7 TeV with the ATLAS detector. Phys. Rev. D, 84(1), 011101–18pp.
Abstract: A search for contact interactions has been performed using dimuon events recorded with the ATLAS detector in proton-proton collisions at root s = 7 TeV. The data sample corresponds to an integrated luminosity of 42 pb(-1). No significant deviation from the standard model is observed in the dimuon mass spectrum, allowing the following 95% C. L. limits to be set on the energy scale of contact interactions: Lambda > 4: 9 TeV (4.5 TeV) for constructive (destructive) interference in the left-left isoscalar compositeness model. These limits are the most stringent to date for μμqq contact interactions.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2011). Measurement of the Z -> tau tau cross section with the ATLAS detector. Phys. Rev. D, 84(11), 112006–29pp.
Abstract: The Z -> tau tau cross section is measured with the ATLAS experiment at the LHC in four different final states determined by the decay modes of the tau leptons: muon-hadron, electron-hadron, electron-muon, and muon-muon. The analysis is based on a data sample corresponding to an integrated luminosity of 36 pb(-1), at a proton-proton center-of-mass energy of root s = 7 TeV. Cross sections are measured separately for each final state in fiducial regions of high detector acceptance, as well as in the full phase space, over the mass region 66-116 GeV. The individual cross sections are combined and the product of the total Z production cross section and Z -> tau tau branching fraction is measured to be 0.97 +/- 0.07(stat) +/- 0.06(syst) +/- 0: 03(lumi) nb, in agreement with next-to-next-to-leading order calculations.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2011). Properties of jets measured from tracks in proton-proton collisions at center-of-mass energy sqrt(s)=7 TeV with the ATLAS detector. Phys. Rev. D, 84(5), 054001–27pp.
Abstract: Jets are identified and their properties studied in center-of-mass energy sqrt(s) = 7 TeV proton-proton collisions at the Large Hadron Collider using charged particles measured by the ATLAS inner detector. Events are selected using a minimum bias trigger, allowing jets at very low transverse momentum to be observed and their characteristics in the transition to high-momentum fully perturbative jets to be studied. Jets are reconstructed using the anti-k(t) algorithm applied to charged particles with two radius parameter choices, 0.4 and 0.6. An inclusive charged jet transverse momentum cross section measurement from 4 GeV to 100 GeV is shown for four ranges in rapidity extending to 1.9 and corrected to charged particle-level truth jets. The transverse momenta and longitudinal momentum fractions of charged particles within jets are measured, along with the charged particle multiplicity and the particle density as a function of radial distance from the jet axis. Comparison of the data with the theoretical models implemented in existing tunings of Monte Carlo event generators indicates reasonable overall agreement between data and Monte Carlo. These comparisons are sensitive to Monte Carlo parton showering, hadronization, and soft physics models.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2011). Study of jet shapes in inclusive jet production in pp collisions at sqrt(s)=7 TeV using the ATLAS detector. Phys. Rev. D, 83(5), 052003–29pp.
Abstract: Jet shapes have been measured in inclusive jet production in proton-proton collisions at root s = 7 TeV using 3 pb(-1) of data recorded by the ATLAS experiment at the LHC. Jets are reconstructed using the anti-k(t) algorithm with transverse momentum 30 GeV < p(T) < 600 GeV and rapidity in the region vertical bar y vertical bar < 2.8. The data are corrected for detector effects and compared to several leading-order QCD matrix elements plus parton shower Monte Carlo predictions, including different sets of parameters tuned to model fragmentation processes and underlying event contributions in the final state. The measured jets become narrower with increasing jet transverse momentum and the jet shapes present a moderate jet rapidity dependence. Within QCD, the data test a variety of perturbative and nonperturbative effects. In particular, the data show sensitivity to the details of the parton shower, fragmentation, and underlying event models in the Monte Carlo generators. For an appropriate choice of the parameters used in these models, the data are well described.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2011). Search for pair production of first or second generation leptoquarks in proton-proton collisions at sqrt(s)=7 TeV using the ATLAS detector at the LHC. Phys. Rev. D, 83(11), 112006–24pp.
Abstract: This paper describes searches for the pair production of first or second generation scalar leptoquarks using 35 pb(-1) of proton-proton collision data recorded by the ATLAS detector at root s = 7 TeV. Leptoquarks are searched in events with two oppositely-charged muons or electrons and at least two jets, and in events with one muon or electron, missing transverse momentum and at least two jets. After event selection, the observed yields are consistent with the predicted backgrounds. Leptoquark production is excluded at the 95% CL for masses M-LQ < 376 (319) GeV and M-LQ < 422 (362) GeV for first and second generation scalar leptoquarks, respectively, when assuming the branching fraction of a leptoquark to a charged lepton is equal to 1.0 (0.5).
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2011). Measurement of the inclusive isolated prompt photon cross section in pp collisions at sqrt(s)=7 TeV with the ATLAS detector. Phys. Rev. D, 83(5), 052005–31pp.
Abstract: A measurement of the cross section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy root s = 7 TeV is presented. The measurement covers the pseudorapidity ranges vertical bar eta(gamma)vertical bar < 1: 37 and 1: 52 <= vertical bar eta(gamma)vertical bar < 1: 81 in the transverse energy range 15 <= E-T(gamma) < 100 GeV. The results are based on an integrated luminosity of 880 nb(-1), collected with the ATLAS detector at the Large Hadron Collider. Photon candidates are identified by combining information from the calorimeters and from the inner tracker. Residual background in the selected sample is estimated from data based on the observed distribution of the transverse isolation energy in a narrow cone around the photon candidate. The results are compared to predictions from next-to-leading-order perturbative QCD calculations.
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