469 research outputs found

    Lepton Flavor Violation in SUSY GUT Model with Non-universal Sfermion Masses

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    We analyze lepton flavor violating τμγ\tau \to \mu \gamma and μeγ\mu \to e \gamma processes in SUSY GUT model in which sfermions have special mass spectrum. It is assumed that only third generation sfermions which are contained in 10(Q,Uc,Ec){\bf 10}(Q, U^c, E^c) of SU(5) can have a different mass from the others. This mass spectrum is led from E6E_6 GUT model with horizontal symmetries. It is shown that branching ratios of τμγ\tau \to \mu \gamma and μeγ\mu \to e \gamma depend strongly on a right-handed stau mass. The weak scale stability requires the light stau, so large decay rates can be expected in this scenario. When stau is around 150 GeV and tanβ10\tan \beta \sim 10, the branching ratios can be larger than Br(τμγ)108Br(\tau \to \mu \gamma) \simeq 10^{-8} and Br(μeγ)5×1012Br(\mu \to e \gamma) \simeq 5\times 10^{-12}, which are within reach of future experiments. In addition, this model has an interesting feature that the final state charged lepton tends to have the right-handed chirality.Comment: 17 pages, 12 figures, v3 a reference adde

    Determining the Neutrino Mass Hierarchy with Atmospheric Neutrinos

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    The possibility to determine the type of neutrino mass hierarchy by studying atmospheric neutrino oscillations with a detector capable to distinguish between neutrino and antineutrino events, such as magnetized iron calorimeters, is considered. We discuss how the ability to distinguish between the neutrino mass spectrum with normal and inverted hierarchy depends on detector characteristics like neutrino energy and direction resolutions or charge miss-identification, and on the systematical uncertainties related to the atmospheric neutrino fluxes. We show also how the neutrino mass hierarchy determination depends on the true values of θ13\theta_{13} and θ23\theta_{23}, as well as on the type of the true hierarchy. We find that for μ\mu-like events, an accurate reconstruction of the energy and direction of the neutrino greatly improves the sensitivity to the type of neutrino mass spectrum. For sin22θ130.1\sin^22\theta_{13} \cong 0.1 and a precision of 5% in the reconstruction of the neutrino energy and 55^\circ in the neutrino direction, the type of neutrino mass hierarchy can be identified at the 2σ\sigma C.L. with approximately 200 events. For resolutions of 15% for the neutrino energy and 1515^\circ for the neutrino direction roughly one order of magnitude larger event numbers are required. For a detector capable to distinguish between νe\nu_e and νˉe\bar\nu_e induced events the requirements on energy and direction resolutions are, in general, less demanding than for a detector with muon charge identification.Comment: 24 pages, 8 figure

    Phenomenological constraints on minimally coupled exotic lepton triplets

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    By introducing a set of new triplet leptons (with nonzero hypercharge) that can Yukawa couple to their Standard Model counterparts, new sources of tree-level flavor changing currents are induced via mixing. In this work, we study some of the consequences of such new contributions on processes such as the leptonic decays of gauge bosons, 3\ell \rightarrow 3\ell' and γ\ell \rightarrow \ell' \gamma which violate lepton flavor, and mu-e conversion in atomic nuclei. Constraints are then placed on the parameters associated with the exotic triplets by invoking the current low-energy experimental data. Moreover, the new physics contribution to the lepton anomalous magnetic moments is calculated.Comment: 17 pages, 1 figure, 2 tables (REVTeX4.1); v2: refs added, to appear in PR

    Neutrino Mass Hierarchy Determination Using Reactor Antineutrinos

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    Building on earlier studies, we investigate the possibility to determine the type of neutrino mass spectrum (i.e., "the neutrino mass hierarchy") in a high statistics reactor electron antineutrino experiment with a relatively large KamLAND-like detector and an optimal baseline of 60 Km. We analyze systematically the Fourier Sine and Cosine Transforms (FST and FCT) of simulated reactor antineutrino data with reference to their specific mass hierarchy-dependent features discussed earlier in the literature. We perform also a binned \chi^2 analysis of the sensitivity of simulated reactor electron antineutrino event spectrum data to the neutrino mass hierarchy, and determine, in particular, the characteristics of the detector and the experiment (energy resolution, visible energy threshold, exposure, systematic errors, binning of data, etc.), which would allow us to get significant information on, or even determine, the type of the neutrino mass spectrum. We find that if \sin^2 2\theta_{13} is sufficiently large, \sin^2 2\theta_{13} \gtap 0.02, the requirements on the set-up of interest are very challenging, but not impossible to realize.Comment: 32 pages, 27 figures, accepted in Journal of High Energy Physic

    Addendum: Neutrino Mass Hierarchy Determination Using Reactor Antineutrinos

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    We update our study of neutrino mass hierarchy determination using a high statistics reactor electron anti-neutrino experiment in the light of the recent evidences of a relatively large non-zero value of \theta_{13} from the Daya Bay and RENO experiments. We find that there are noticeable modifications in the results, which allow a relaxation in the detector's characteristics, such as the energy resolution and exposure, required to obtain a significant sensitivity to, or to determine, the neutrino mass hierarchy in such a reactor experiment.Comment: 7 pages, 1 figure, to be published in Journal of High Energy Physics (JHEP