The centrality dependence of the mean charged-particle multiplicity as a function of pseudorapidity is measured in approximately 1 mu b(-1) of proton-lead collisions at a nucleon-nucleon centre-of-mass energy of root s(NN) = 5.02 TeV using the ATLAS detector at the Large Hadron Collider. Charged particles with absolute pseudorapidity less than 2.7 are reconstructed using the ATLAS pixel detector. The p + Pb collision centrality is characterised by the total transverse energy measured in the Pb-going direction of the forward calorimeter. The charged-particle pseudorapidity distributions are found to vary strongly with centrality, with an increasing asymmetry between the proton-going and Pb-going directions as the collisions become more central. Three different estimations of the number of nucleons participating in the p + Pb collision have been carried out using the Glauber model as well as two Glauber-Gribov inspired extensions to the Glauber model. Charged-particle multiplicities per participant pair are found to vary differently for these three models, highlighting the importance of including colour fluctuations in nucleon-nucleon collisions in the modelling of the initial state of p + Pb collisions.

Citation Aad, G., B. Abbott, J. Abdallah, S. Abdel Khalek, O. Abdinov, R. Aben, B. Abi, et al. 2015. “Erratum to: Search for production of WW / WZ resonances decaying to a lepton, neutrino and jets in pp collisions at documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} begin{document}$$sqrt{s}=8$$end{document}s=8 TeV with the ATLAS detector.” The European Physical Journal. C, Particles and Fields 75 (8): 370. doi:10.1140/epjc/s10052-0153593-4. http://dx.doi.org/10.1140/epjc/s10052-015-3593-4.

This paper presents cross sections for the production of a W boson in association with jets, measured in proton–proton collisions at √ s = 7 TeV with the ATLAS experiment at the large hadron collider. With an integrated luminosity of 4.6 fb−1, this data set allows for an exploration of a large kinematic range, including jet production up to a transverse momentum of 1 TeV and multiplicities up to seven associated jets. The production cross sections for W bosons are measured in both the electron and muon decay channels. Differential cross sections for many observables are also presented including measurements of the jet observables such as the rapidities and the transverse momenta as well as measurements of event observables such as the scalar sums of the transverse momenta of the jets. The measurements are compared to numerous QCD predictions including next-toleading-order perturbative calculations, resummation calculations and Monte Carlo generators.

Measurements of fiducial cross sections for the electroweak production of two jets in association with a Z -boson are presented. The measurements are performed using 20 . 3 fb −1 of proton-proton collision data collected at a centre-of-mass energy of √(s) = 8 TeV by the ATLAS experiment at the Large Hadron Collider. The electroweak component is extracted by a fit to the dijet invariant mass distribution in a fiducial region chosen to enhance the electroweak contribution over the dominant background in which the jets are produced via the strong interaction. The electroweak cross sections measured in two fiducial regions are in good agreement with the Standard Model expectations and the background-only hypothesis is rejected with significance above the 5 σ level. The electroweak process includes the vector boson fusion production of a Z -boson and the data are used to place limits on anomalous triple gauge boson couplings. In addition, measurements of cross sections and differential distributions for inclusive Z -boson-plus-dijet production are performed in five fiducial regions, each with different sensitivity to the electroweak contribution. The results are corrected for detector effects and compared to predictions from the Sherpa and Powheg event generators.

A blind analysis searching for the decay B-s(0) -> mu(+)mu(-) has been performed using proton-proton collisions at a centre-of-mass energy of 7 TeV recorded with the ATLAS detector at the LHC. With an integrated luminosity of 2.4 fb(-1) no excess of events over the background expectation is found and an upper limit is set on the branching fraction BR(B-s(0) -> mu(+)mu(-)) <2.2(1.9) x 10(-8) at 95% (90%) confidence level. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.