2,624 research outputs found

    Determination of QCD Backgrounds in ATLAS: A challenge for SUSY searches

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    In this paper we briefly discuss the estimation of uncertainties in QCD backgrounds to searches for Supersymmetry under development by the ATLAS collaboration.Comment: Proceedings of SUY09. Boston (USA

    Fake Missing Transverse Energy from Calorimeter Effects

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    In this paper we discuss briefly the correlation between fake missing transverse energy and jets pointing to crack regions in the ATLAS calorimeters.Comment: Prepared for the BSM-LHC Whitepaper (Nuclear Physics B

    Searching for doubly-charged vector bileptons in the Golden Channel at the LHC

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    In this paper we investigate the LHC potential for discovering doubly-charged vector bileptons considering the measurable process p,pp,p \rightarrow eeμ±μ±Xe^{\mp}e^{\mp}\mu^{\pm}\mu^{\pm} X. We perform the study using four different bilepton masses and three different exotics quark masses. Minimal LHC integrated luminosities needed for discovering and for setting limits on bilepton masses are obtained for both 7 TeV and 14 TeV center-of-mass energies. We find that these spectacular signatures can be observed at the LHC in the next years up to a bilepton mass of order of 1 TeV.Comment: 8 pages, 10 figure

    Virtual bilepton effects in polarized Moller scattering

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    We investigate the indirect effects of heavy vector bileptons being exchanged in polarized Moller scattering, at the next generation of linear colliders. Considering both longitudinal and transverse beam polarization, and accounting for initial-state radiation, beamstrahlung and beam energy spread, we discuss how angular distributions and asymmetries can be used to detect clear signals of virtual bileptons, and the possibility of distinguishing theoretical models that incorporate these exotic particles. We then estimate 95% C.L. bounds on the mass of these vector bileptons and on their couplings to electrons.Comment: 19 pages, 10 figure

    Time of Flight Analysis Using Cosmic Ray Muons in the ATLAS Tile Calorimeter

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    Using cosmic ray muon data recorded during the summer of 2007, we have studied the time-of-flight distributions between back-to-back modules of the ATLAS Tile Calorimeter. The results are in good agreement with the distributions expected from calorimeter geometry, and allow for cross-checks of timing corrections obtained in laser runs. Calorimeter timing is a useful tool to remove non-physics backgrounds, and we introduce new cuts at the cell level which improve the signal-to-noise ratio

    The HIBEAM/NNBAR Calorimeter Prototype

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    The HIBEAM/NNBAR experiment is a free-neutron search for nn \rightarrow sterile nn and nnˉn \rightarrow \bar{n} oscillations planned to be installed at the European Spallation Source under construction in Lund, Sweden. A key component in the experiment is the detector to identify nnˉn-\bar{n} annihilation events, which will produce on average four pions with a final state invariant mass of two nucleons, around 1.91.9\,GeV. The beamline and experiment are shielded from magnetic fields which would suppress nnˉn \rightarrow \bar{n} transitions, thus no momentum measurement will be possible. Additionally, calorimetry for particles with kinetic energies below 600600\,MeV is challenging, as traditional sampling calorimeters used in HEP would suffer from poor shower statistics. A design study is underway to use a novel approach of a hadronic range measurement in multiple plastic scintillator layers, followed by EM calorimetery with lead glass. A prototype calorimeter system is being built, and will eventually be installed at an ESS test beam line for \textit{in situ} neutron background studies.Comment: Contribution to the International Conference on Technology and Instrumentation in Particle Physics (TIPP2021

    Explaining the Higgs Decays at the LHC with an Extended Electroweak Model

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    We show that the recent discovery of a new boson at the LHC, which we assume to be a Higgs boson, and the observed enhancement in its diphoton decays compared to the SM prediction, can be explained by a new doublet of charged vector bosons from an extended electroweak gauge sector model with SU(3)_C\otimesSU(3)_L\otimesU(1)_X symmetry. Our results show a good agreement between our theoretical expected sensitivity to a 126--125 GeV Higgs boson and the experimental significance observed in the diphoton channel at the 8 TeV LHC. Effects of an invisible decay channel for the Higgs boson are also taken into account, in order to anticipate a possible confirmation of deficits in the branching ratios into ZZZZ^*, WWWW^*, bottom quarks, and tau leptons.Comment: 16 pages, 5 figure

    Searching for vector bileptons in polarized Bhabha scattering

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    In this paper we analyze the effects of virtual vector bileptons in polarized Bhabha scattering at the energies of the future linear colliders. In order to make the calculations of the differential cross sections more realistic, important beam effects such as initial state radiation, beamstrahlung, beam energy and polarization spreads are accounted for. The finite resolution of a typical electromagnetic calorimeter planned for the new linear colliders is also considered in the simulation. The 95% confidence level limits for bilepton masses in 331 models are evaluated.Comment: Accepted for publication in the Journal of Physics G: Nuclear and Particle Physic

    Hunt for new phenomena using large jet multiplicities and missing transverse momentum with ATLAS in 4.7 fb−1 of s√=7TeV proton-proton collisions

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    Results are presented of a search for new particles decaying to large numbers of jets in association with missing transverse momentum, using 4.7 fb−1 of pp collision data at s√=7TeV collected by the ATLAS experiment at the Large Hadron Collider in 2011. The event selection requires missing transverse momentum, no isolated electrons or muons, and from ≥6 to ≥9 jets. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of a MSUGRA/CMSSM supersymmetric model, where, for large universal scalar mass m 0, gluino masses smaller than 840 GeV are excluded at the 95% confidence level, extending previously published limits. Within a simplified model containing only a gluino octet and a neutralino, gluino masses smaller than 870 GeV are similarly excluded for neutralino masses below 100 GeV

    Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC