274 research outputs found

    Massively Parallel Computing at the Large Hadron Collider up to the HL-LHC

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    As the Large Hadron Collider (LHC) continues its upward progression in energy and luminosity towards the planned High-Luminosity LHC (HL-LHC) in 2025, the challenges of the experiments in processing increasingly complex events will also continue to increase. Improvements in computing technologies and algorithms will be a key part of the advances necessary to meet this challenge. Parallel computing techniques, especially those using massively parallel computing (MPC), promise to be a significant part of this effort. In these proceedings, we discuss these algorithms in the specific context of a particularly important problem: the reconstruction of charged particle tracks in the trigger algorithms in an experiment, in which high computing performance is critical for executing the track reconstruction in the available time. We discuss some areas where parallel computing has already shown benefits to the LHC experiments, and also demonstrate how a MPC-based trigger at the CMS experiment could not only improve performance, but also extend the reach of the CMS trigger system to capture events which are currently not practical to reconstruct at the trigger level.Comment: 14 pages, 6 figures. Proceedings of 2nd International Summer School on Intelligent Signal Processing for Frontier Research and Industry (INFIERI2014), to appear in JINST. Revised version in response to referee comment

    Data Driven Search in the Displaced bbˉb\bar{b} Pair Channel for a Higgs Boson Decaying to Long-Lived Neutral Particles

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    This article presents a proposal for a new search channel for the Higgs boson decaying to two long-lived neutral particles, each of which decays to bbˉb\bar b at a displaced vertex. The decay length considered is such that the decay takes place within the LHC beampipe. We present a new data-driven analysis using jet substructure and properties of the tracks from the highly-displaced vertices. We consider a model with a 125 GeV Higgs boson with a significant branching fraction to decay via this mode, with the long-lived neutral particle having a mass in the range of 15--40 GeV and a decay length commensurate with the beam pipe radius. Such a signal can be readily observed with an integrated luminosity of 19.5 fb1^{-1} at 8TeV at the LHC.Comment: 16 pages, 8 figures, Submitted to JHE

    Evaluation of the Theoretical Uncertainties in the W to Lepton and Neutrino Cross Sections at the LHC

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    We study the sources of systematic errors in the measurement of the W to lepton and neutrino cross-sections at the LHC. We consider the systematic errors in both the total cross-section and acceptance for anticipated experimental cuts. We include the best available analysis of QCD effects at NNLO in assessing the effect of higher order corrections and PDF and scale uncertainties on the theoretical acceptance. In addition, we evaluate the error due to missing NLO electroweak corrections and propose which MC generators and computational schemes should be implemented to best simulate the events.Comment: 33 pages, 109 eps figures, uses JHEP3.cls, rotating.sty Version 2 corrects an error in Table 1, adds some references, and updates an author addres

    Dilaton Supersymmetry Breaking

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    We argue that dilaton supersymmetry breaking in string derived supergravity requires an effective superpotential which is not separable as a function of the dilaton times a function of the moduli. We show that in a simple model with hidden sector matter condensation and a dilaton independent term one can easily obtain FS0|F_S| \not=0. For a wide range of realistic model parameters FS>>FT|F_S|>>|F_T| and supersymmetry is mainly broken in the dilaton direction.Comment: 11 pages, uses phyzzx.te