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The simulation software for the ATLAS Experiment at the Large Hadron Collider is being used for largescale production of events on the LHC Computing Grid. This simulation requires many components, from the generators that simulate particle collisions, through packages simulating the response of the various detectors and triggers. All of these components come together under the AT-LAS simulation infrastructure. In this paper, that infrastructure is discussed, including that supporting the detector description, interfacing the event generation, and combining the GEANT4 simulation of the response of the individual detectors. Also described are the tools allowing the software validation, performance testing, and the validation of the simulated output against known physics processes.

ALICE is the heavy-ion experiment at the CERN Large Hadron Collider. The experiment continuously took data during the first physics campaign of the machine from fall 2009 until early 2013, using proton and lead-ion beams. In this paper we describe the running environment and the data handling procedures, and discuss the performance of the ALICE detectors and analysis methods for various physics observables.

The luminosity calibration for the ATLAS detector at the LHC during pp collisions at in 2010 and 2011 is presented. Evaluation of the luminosity scale is performed using several luminosity-sensitive detectors, and comparisons are made of the long-term stability and accuracy of this calibration applied to the pp collisions at . A luminosity uncertainty of is obtained for the 47 pb−1 of data delivered to ATLAS in 2010, and an uncertainty of is obtained for the 5.5 fb−1 delivered in 2011.

This paper presents a search for direct electroweak gaugino or gluino pair production with a chargino nearly mass-degenerate with a stable neutralino. It is based on an integrated luminosity of 36.1 fb −1 of pp collisions at √ s = 13 TeV collected by the ATLAS experiment at the LHC. The final state of interest is a disappearing track accompanied by at least one jet with high transverse momentum from initial-state radiation or by four jets from the gluino decay chain. The use of short track segments reconstructed from the innermost tracking layers significantly improves the sensitivity to short chargino lifetimes. The results are found to be consistent with Standard Model predictions. Exclusion limits are set at 95% confidence level on the mass of charginos and gluinos for different chargino lifetimes. For a pure wino with a lifetime of about 0.2 ns, chargino masses up to 460 GeV are excluded. For the strong production channel, gluino masses up to 1.65 TeV are excluded assuming a chargino mass of 460 GeV and lifetime of 0.2 ns. Keywords: Hadron-Hadron scattering (experiments)ArXiv ePrint: 1712.02118Open Access, Copyright CERN, for the benefit of the ATLAS Collaboration. Article funded by SCOAP 3 .https://doi.org/10.1007/JHEP06 (2018) [7], SUSY particles are produced in pairs and decay such that their final products consist only of SM particles and the stable lightest supersymmetric particle (LSP). In many supersymmetric models, the supersymmetric partners of the SM W boson fields, the wino fermions, are the lightest gaugino states. In this case, the lightest of the charged mass eigenstates, a chargino, and the lightest of the neutral mass eigenstates, a neutralino, are both almost pure wino and nearly mass-degenerate. As a result, the lightest chargino can have a lifetime long enough that it can reach the AT-LAS detector before decaying. For example, anomaly-mediated supersymmetry breaking (AMSB) scenarios [8,9] naturally predict a pure wino LSP, which is a dark-matter candidate. The mass-splitting between the charged and neutral wino (∆mχ 1 ) in such models is suppressed at tree level by the approximate custodial symmetry; it has been calculated at the two-loop level to be around 160 MeV [10], corresponding to a chargino lifetime of about 0.2 ns [11]. This prediction for the value of the lifetime is actually a general feature of models with a wino LSP: within the generated models of the ATLAS phenomenological Minimal Supersymmetric Standard Model (pMSSM) scan [12] that have a wino-like LSP, about 70% have a charged-wino lifetime between 0.15 ns and 0.25 ns. Most of the models in the other 30% have a larger mass-splitting (and therefore the charged wino has a shorter lifetime) due to a non-decoupled higgsino mass. The search presented here is sensitive to a wide range of lifetimes, from 10 ps to 10 ns, and reaches maximum sensitivity for lifetimes around 1 ns.The decay products of SUSY particles that are strongly mass-degenerate with the lightest neutralino leave little visible energy in the detector. T...