Centrality and rapidity dependence of inclusive jet production in root(NN)-N-S=5.02 TeV proton-lead collisions with the ATLAS detector

Measurements of the centrality and rapidity dependence of inclusive jet production in root(NN)-N-S = 5.02 TeV proton-lead (p + Pb) collisions and the jet cross-section in root s = 2.76 TeV proton-proton collisions are presented. These quantities are measured in datasets corresponding to an integrated luminosity of 27.8 nb(-1) and 4.0 pb(-1), respectively, recorded with the ATLAS detector at the Large Hadron Collider in 2013. The p + Pb collision centrality was characterised using the total transverse energy measured in the pseudorapidity interval -4.9 < eta < -3.2 in the direction of the lead beam. Results are presented for the double-differential per-collision yields as a function of jet rapidity and transverse momentum (p(T)) for minimum-bias and centrality-selected p + Pb collisions, and are compared to the jet rate from the geometric expectation. The total jet yield in minimum-bias events is slightly enhanced above the expectation in a p(T)-dependent manner but is consistent with the expectation within uncertainties. The ratios of jet spectra from different centrality selections show a strong modification of jet production at all p(T) at forward rapidities and for large pT at mid-rapidity, which manifests as a suppression of the jet yield in central events and an enhancement in peripheral events. These effects imply that the factorisation between hard and soft processes is violated at an unexpected level in proton-nucleus collisions. Furthermore, the modifications at forward rapidities are found to be a function of the total jet energy only, implying that the violations may have a simple dependence on the hard parton-parton kinematics. (C) 2015 CERN for the benefit of the ATLAS Collaboration. Published by Elsevier B.V

Search for a standard model Higgs boson in the H -> ZZ -> l(+)l(-) nu(nu)over-bar decay channel using 4.7 fb(-1) of root s=7 TeV data with the ATLAS detector

A search for a Standard Model Higgs boson decaying via H -> ZZ -> l(+)l(-) nu(nu) over bar, where l represents electrons or muons, is presented. It is based on proton-proton collision data at root s = 7 TeV, collected by the ATLAS experiment at the LHC during 2011 and corresponding to an integrated luminosity of 4.7 fb(-1). The data agree with the expected Standard Model backgrounds. Upper limits on the Higgs boson production cross section are derived for Higgs boson masses between 200 GeV and 600 GeV and the production of a Standard Model Higgs boson with a mass in the range 319-558 GeV is excluded at the 95% confidence level. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved

Search for the Standard Model Higgs boson in the decay channel H→ZZ(*)→4ℓ with the ATLAS detector

A search for the Standard Model Higgs boson in the decay channel H -> ZZ(()*()) l(+)l(-)l'l'(-), where l = e, mu, is presented. Proton-proton collision data at root s = 7 TeV recorded with the ATLAS detector and corresponding to an average integrated luminosity of 2.1 fb(-1) are compared to the Standard Model expectations. Upper limits on the production cross section of a Standard Model Higgs boson with a mass between 110 and 600 GeV are derived. The observed (expected) 95% confidence level upper limit on the production cross section for a Higgs boson with a mass of 194 GeV, the region with the best expected sensitivity for this search, is 0.99 (1.01) times the Standard Model prediction. The Standard Model Higgs boson is excluded at 95% confidence level in the mass ranges 191-197, 199-200 and 214-224 GeV. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved

Measurement of the W(+/-)Z production cross section and limits on anomalous triple gauge couplings in proton-proton collisions at root s=7 TeV with the ATLAS detector

This Letter presents a measurement of W(+/-)Z production in 1.02 fb(-1) of pp collision data at root s = 7 TeV collected by the ATLAS experiment in 2011. Doubly leptonic decay events are selected with electrons, muons and missing transverse momentum in the final state. In total 71 candidates are observed, with a background expectation of 12.1 +/- 1.4(stat.)(-2.0)(+4.1)(syst.) events. The total cross section for W(+/-)Z production for Z/gamma* masses within the range 66 GeV to 116 GeV is determined to be sigma(tot)(WZ) = 20.5(-2.8)(+3.1)(stat.)(-1.3)(+1.4)(syst)(-0.8)(+0.9)(lumi.) pb, which is consistent with the Standard Model expectation of 17.3(0.8)(+1.3) pb. Limits on anomalous triple gauge boson couplings are extracted. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved. RI Doyle, Anthony/C-5889-2009; Pina, Joao /C-4391-2012; Li, Xuefei/C-3861-2012; Fazio, Salvatore /G-5156-2010; Smirnova, Lidia/D-8089-2012; Sivoklokov, Sergey/D-8150-2012; Smirnov, Sergei/F-1014-2011; Gladilin, Leonid/B-5226-2011; Barreiro, Fernando/D-9808-2012; Kramarenko, Victor/E-1781-2012; Prokoshin, Fedor/E-2795-2012; valente, paolo/A-6640-2010; Alexa, Calin/F-6345-2010; Gutierrez, Phillip/C-1161-2011; Pacheco Pages, Andres/C-5353-2011; Moorhead, Gareth/B-6634-2009; Livan, Michele/D-7531-2012; Takai, Helio/C-3301-2012; Petrucci, Fabrizio/G-8348-2012; Wemans, Andre/A-6738-2012; Jones, Roger/H-5578-2011; Fabbri, Laura/H-3442-2012; Kurashige, Hisaya/H-4916-2012; Villa, Mauro/C-9883-2009; Delmastro, Marco/I-5599-201

Search for the Standard Model Higgs boson in the decay channel H -&gt; ZZ(()*()) -&gt; 4l with the ATLAS detector

A search for the Standard Model Higgs boson in the decay channel H→ZZ(*)→ℓ+ℓ-ℓ'+ℓ'-, where ℓ=e, μ, is presented. Proton-proton collision data at s=7TeV recorded with the ATLAS detector and corresponding to an average integrated luminosity of 2.1fb-1 are compared to the Standard Model expectations. Upper limits on the production cross section of a Standard Model Higgs boson with a mass between 110 and 600GeV are derived. The observed (expected) 95% confidence level upper limit on the production cross section for a Higgs boson with a mass of 194 GeV, the region with the best expected sensitivity for this search, is 0.99 (1.01) times the Standard Model prediction. The Standard Model Higgs boson is excluded at 95% confidence level in the mass ranges 191-197, 199-200 and 214-224 GeV. © 2011 CERN

Search for contact interactions in dilepton events from pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

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 sqrt(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 mu+ mu- channels, respectively. No significant deviations from the standard model are observed. Using a Bayesian approach with a prior flat in 1/Lambda^2, the following 95% CL lower limits are placed on the energy scale of llqq contact interactions: Lambda^- > 10.1 TeV (Lambda^+ > 9.4 TeV) in the electron channel and Lambda^- > 8.0 TeV (Lambda^+ > 7.0 TeV) in the muon channel for constructive (destructive) interference in the left-left isoscalar contact interaction model. Limits are also provided for a prior flat in 1/Lambda^4