1,985 research outputs found

    CTA in the Context of Searches for Particle Dark Matter - a glimpse

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    In this contribution, CTAs potential role in detection of particle dark matter in the context of other detection approaches is briefly discussed for an audience of gamma-ray astronomers. In particular searches for new particles at the large hadron collider and detection of dark matter particles in deep underground detectors are considered. We will focus on Weakly Interacting Massive Particles (WIMP). Approaches will be compared in terms of (a) robustness of sensitivity predictions, (b) timeline and (c) reach. The estimate of the reach will be model-dependent. Given our ignorance about the nature of dark matter, and the complementarity of detection techniques even within a given framework (e.g. Supersymmetry), the trivial conclusion is that we might need all approaches and the most sensitive experiments. Our discussion will be somewhat more restrictive in order to be able to be more concrete. With the caveat of incompleteness, under the assumption that the WIMP paradigm describes nature, CTA is more likely to discover multi-TeV WIMP dark matter, whereas for lower masses direct detection and LHC has significantly better prospects. We will illustrate this conclusion with examples from foremost Supersymmetry, but mention effective field theory or simplified models. We will comment on a few models predicting high mass WIMPs, in particular 1 TeV higgsino and wino WIMPs, as well as Minimal Dark Matter and point out the relevance of updated measurements of the anomalous magnetic moment of the muon for CTAs role in searches for Supersymmetry.Comment: Invited contribution to 6th International Symposium on High-Energy Gamma-ray Astronomy (Gamma2016). 9 pages, 5 figure

    Searches for Particle Dark Matter with gamma-rays

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    In this contribution I review the present status and discuss some prospects for indirect detection of dark matter with gamma-rays. Thanks to the Fermi Large Area Telescope, searches in gamma-rays have reached sensitivities that allow to probe the most interesting parameter space of the weakly interacting massive particles (WIMP) paradigm. This gain in sensitivity is naturally accompanied by a number of detection claims or indications, the most recent being the claim of a line feature at a dark matter particle mass of ∌\sim 130 GeV at the Galactic Centre, a claim which requires confirmation from the Fermi-LAT collaboration and other experiments, for example HESS II or the planned Gamma-400 satellite. Predictions for the next generation air Cherenkov telescope, Cherenkov Telescope Array (CTA), together with forecasts on future Fermi-LAT constraints arrive at the exciting possibility that the cosmological benchmark cross-section could be probed from masses of a few GeV to a few TeV. Consequently, non-detection would pose a challenge to the WIMP paradigm, but the reached sensitivities also imply that --optimistically-- a detection is in the cards.Comment: Invited "compact review", 5th International Symposium on High Energy Gamma-Ray Astronomy (Gamma 2012), Heidelberg, 11 pages, 3 figure

    On Fractional Instanton Numbers in Six Dimensional Heterotic E8 x E8 Orbifolds

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    We derive the precise relation between level matching condition and fractional instanton numbers in six dimensional, abelian and supersymmetric orbifolds of E8 x E8 heterotic string theory. The fractional part of the two E8 instanton numbers is explicitly calculated in terms of the gauge twist. This relation is then used to show that the classification of these orbifolds can be given in terms of flat bundles away from the orbifold singularities under the only constraint that the sum of the fractional parts of the gauge instanton numbers match the fractional part of the gravitational instanton number locally at every fixed point. This directly carries over to M-theory on S^1/Z_2Comment: latex2e, 12 pages; reference and comments adde

    Likelihood ratio intervals with Bayesian treatment of uncertainties: coverage, power and combined experiments

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    In this note we present studies of coverage and power for confidence intervals for a Poisson process with known background calculated using the Likelihood ratio (aka Feldman & Cousins) ordering with Bayesian treatment of uncertainties in nuisance parameters. We consider both the variant where the Bayesian integration is done in both the numerator and the denominator and the modification where the integration is done only in the numerator whereas in the denominator the likelihood is taken at the maximum likelihood estimate of the parameters. Furthermore we discuss how measurements can be combined in this framework and give an illustration with limits on the branching ratio of a rare B-meson decay recently presented by CDF/D0. A set of C++ classes has been developed which can be used to calculate confidence intervals for single or combining multiple experiments using the above algorithms and considering a variety of parameterizations to describe the uncertainties.Comment: 4 pages, 3 figures, to appear in proceedings of PhyStat2005, Oxford, UK, Sept 2005, Imperial College Pres