The jet energy scale (JES) and its systematic uncertainty are determined for jets measured with the ATLAS detector using proton-proton collision data with a centre-of-mass energy of [Formula: see text] TeV corresponding to an integrated luminosity of [Formula: see text][Formula: see text]. Jets are reconstructed from energy deposits forming topological clusters of calorimeter cells using the anti-[Formula: see text] algorithm with distance parameters [Formula: see text] or [Formula: see text], and are calibrated using MC simulations. A residual JES correction is applied to account for differences between data and MC simulations. This correction and its systematic uncertainty are estimated using a combination of in situ techniques exploiting the transverse momentum balance between a jet and a reference object such as a photon or a [Formula: see text] boson, for [Formula: see text] and pseudorapidities [Formula: see text]. The effect of multiple proton-proton interactions is corrected for, and an uncertainty is evaluated using in situ techniques. The smallest JES uncertainty of less than 1 % is found in the central calorimeter region ([Formula: see text]) for jets with [Formula: see text]. For central jets at lower [Formula: see text], the uncertainty is about 3 %. A consistent JES estimate is found using measurements of the calorimeter response of single hadrons in proton-proton collisions and test-beam data, which also provide the estimate for [Formula: see text] TeV. The calibration of forward jets is derived from dijet [Formula: see text] balance measurements. The resulting uncertainty reaches its largest value of 6 % for low-[Formula: see text] jets at [Formula: see text]. Additional JES uncertainties due to specific event topologies, such as close-by jets or selections of event samples with an enhanced content of jets originating from light quarks or gluons, are also discussed. The magnitude of these uncertainties depends on the event sample used in a given physics analysis, but typically amounts to 0.5-3 %.

The emission of pions from relativistic heavy-ion collisions of S+S, S+Ag and S+Pb at 200 GeV/nucleon is characterized using two-particle interferometry. The multiplicity dependence of the pion source parameters near midrapidity is studied. The transversal ( R t ) and longitudinal ( R l ) pion source parameters are independent of the initial nuclei in the interaction and increase with increasing multiplicity. This suggests that the freeze-out process is governed mainly by the particle multiplicity. The multiplicity dependence is weaker than that expected from a simple model of a freeze-out at a constant density.

The NA44 Collaboration has measured yields and differential distributions of K, Preprint submitted to Elsevier Preprint 28 January 2013 K−, π, π− in transverse kinetic energy and rapidity, around the center-of-mass rapidity in 158 A GeV/c Pb+Pb collisions at the CERN SPS. A considerable enhancement of K production per π is observed, as compared to p + p collisions at this energy. To illustrate the importance of secondary hadron rescattering as an enhancement mechanism, we compare strangeness production at the SPS and AGS with predictions of the transport model RQMD.

A search for doubly charged Higgs bosons decaying to pairs of electrons and/or muons is presented. The search is performed using a data sample corresponding to an integrated luminosity of 4.7 fb−1 of pp collisions at \(\sqrt{s}\) = 7 TeV collected by the ATLAS detector at the LHC. Pairs of prompt, isolated, high-p T leptons with the same electric charge (e ± e ±, e ± μ ±, μ ± μ ±) are selected, and their invariant mass distribution is searched for a narrow resonance. No significant excess over Standard Model background expectations is observed, and limits are placed on the cross section times branching ratio for pair production of doubly charged Higgs bosons. The masses of doubly charged Higgs bosons are constrained depending on the branching ratio into these leptonic final states. Assuming pair production, coupling to left-handed fermions, and a branching ratio of 100 % for each final state, masses below 409 GeV, 375 GeV, and 398 GeV are excluded for e ± e ±, e ± μ ±, and μ ± μ ±, respectively.

A measurement of the $ZZ$ production cross section in proton-proton collisions at $\sqrt{s}=7\text{ }\text{ }\mathrm{TeV}$ using data corresponding to an integrated luminosity of $1.02\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ recorded by the ATLAS experiment at the LHC is presented. Twelve events containing two $Z$ boson candidates decaying to electrons and/or muons are observed, with an expected background of $0.3\ifmmode\pm\else\textpm\fi{}0.3(\mathrm{stat}{)}_{\ensuremath{-}0.3}^{+0.4}(\mathrm{syst})$ events. The cross section measured in a phase-space region with good detector acceptance and for dilepton masses within the range 66 to 116 GeV is ${\ensuremath{\sigma}}_{ZZ\ensuremath{\rightarrow}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}}^{\mathrm{fid}}={19.4}_{\ensuremath{-}5.2}^{+6.3}(\mathrm{stat}{)}_{\ensuremath{-}0.7}^{+0.9}(\mathrm{syst})\ifmmode\pm\else\textpm\fi{}0.7(\mathrm{lumi})\text{ }\text{ }\mathrm{fb}$. The resulting total cross section for on-shell $ZZ$ production, ${\ensuremath{\sigma}}_{ZZ}^{\mathrm{tot}}={8.5}_{\ensuremath{-}2.3}^{+2.7}(\mathrm{stat}{)}_{\ensuremath{-}0.3}^{+0.4}(\mathrm{syst})\ifmmode\pm\else\textpm\fi{}0.3(\mathrm{lumi})\text{ }\text{ }\mathrm{pb}$, is consistent with the standard model expectation of ${6.5}_{\ensuremath{-}0.2}^{+0.3}\text{ }\text{ }\mathrm{pb}$ calculated at the next-to-leading order in QCD. Limits on anomalous neutral triple gauge boson couplings are derived.

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 centre-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.7 fb-1. No excess beyond Standard Model expectations is observed. A W' with Sequential Standard Model couplings is excluded at the 95 credibility level for masses up to 2.55 TeV. Excited chiral bosons (W*) with equivalent coupling strength are excluded for masses up to 2.42 TeV.