3,640 research outputs found

    Statistical Challenges of Global SUSY Fits

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    We present recent results aiming at assessing the coverage properties of Bayesian and frequentist inference methods, as applied to the reconstruction of supersymmetric parameters from simulated LHC data. We discuss the statistical challenges of the reconstruction procedure, and highlight the algorithmic difficulties of obtaining accurate profile likelihood estimates

    Search for Higgs Bosons Decay HγγH\to \gamma\gamma Using Vector Boson Fusion

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    The sensitivity of the ATLAS experiment to low mass SM Higgs produced via Vector Boson Fusion mechanism with HγγH\to \gamma\gamma is invest igated. A cut based event selection has been chosen to optimize the expected signal significance with this decay mode. A signal significance of 2. 2σ \sigma may be achieved for M_H=130 \gev with 30 fb1^{-1} of accumulated luminosity

    A Coverage Study of the CMSSM Based on ATLAS Sensitivity Using Fast Neural Networks Techniques

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    We assess the coverage properties of confidence and credible intervals on the CMSSM parameter space inferred from a Bayesian posterior and the profile likelihood based on an ATLAS sensitivity study. In order to make those calculations feasible, we introduce a new method based on neural networks to approximate the mapping between CMSSM parameters and weak-scale particle masses. Our method reduces the computational effort needed to sample the CMSSM parameter space by a factor of ~ 10^4 with respect to conventional techniques. We find that both the Bayesian posterior and the profile likelihood intervals can significantly over-cover and identify the origin of this effect to physical boundaries in the parameter space. Finally, we point out that the effects intrinsic to the statistical procedure are conflated with simplifications to the likelihood functions from the experiments themselves.Comment: Further checks about accuracy of neural network approximation, fixed typos, added refs. Main results unchanged. Matches version accepted by JHE

    Prospects for Higgs Searches via VBF at the LHC with the ATLAS Detector

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    We report on the potential for the discovery of a Standard Model Higgs boson with the vector boson fusion mechanism in the mass range 115 with the ATLAS experiment at the LHC. Feasibility studies at hadron level followed by a fast detector simulation have been performed for H\to W^{(*)}W^{(*)}\to l^+l^-\sla{p_T}, HγγH\to\gamma\gamma and HZZl+lqqˉH\to ZZ\to l^+l^-q\bar{q}. The results obtained show a large discovery potential in the range 115. Results obtained with multivariate techniques are reported for a number of channels.Comment: 14 pages, 4 figures, contributed to 2003 Les Houches Workshop on Physics at TeV Colliders. Incorporated comments from ATLAS referee

    EventView - The Design Behind an Analysis Framework

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    The development of software used to process petabytes of data per year is an elaborate project. The complexity of the detector means components of very diverse nature are required to process the data and one needs well defined frameworks that are both flexible and maintainable. Modern programming architecture based on object-oriented component design supports desirable features of such frameworks. The principle has been applied in almost all sub-systems of ATLAS software and its robustness has benefited the collaboration. An implementation of such framework for physics analysis, however, did not exist before the work presented in this paper. As it turns out the realisation of object-oriented analysis framework is closely related to the design of the event data object. In this paper, we well review the design behind the analysis framework developed around a data class called ``EventView''. It is a highly integrated part of the ATLAS software framework and is now becoming a standard platform for physics analysis in the collaboration

    Higgs Mass and Muon Anomalous Magnetic Moment in Supersymmetric Models with Vector-Like Matters

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    We study the muon anomalous magnetic moment (muon g-2) and the Higgs boson mass in a simple extension of the minimal supersymmetric (SUSY) Standard Model with extra vector-like matters, in the frameworks of gauge mediated SUSY breaking (GMSB) models and gravity mediation (mSUGRA) models. It is shown that the deviation of the muon g-2 and a relatively heavy Higgs boson can be simultaneously explained in large tan-beta region. (i) In GMSB models, the Higgs mass can be more than 135 GeV (130 GeV) in the region where muon g-2 is consistent with the experimental value at the 2 sigma (1 sigma) level, while maintaining the perturbative coupling unification. (ii) In the case of mSUGRA models with universal soft masses, the Higgs mass can be as large as about 130 GeV when muon g-2 is consistent with the experimental value at the 2 sigma level. In both cases, the Higgs mass can be above 140 GeV if the g-2 constraint is not imposed.Comment: 26 pages; 7 figures; corrected typos; minor change