385 research outputs found

    Higgs coupling constants as a probe of new physics

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    We study new physics effects on the couplings of weak gauge bosons with the lightest CP-even Higgs boson (hh), hZZhZZ, and the tri-linear coupling of the lightest Higgs boson, hhhhhh, at the one loop order, as predicted by the two Higgs doublet model. Those renormalized coupling constants can deviate from the Standard Model (SM) predictions due to two distinct origins; the tree level mixing effect of Higgs bosons and the quantum effect of additional particles in loop diagrams. The latter can be enhanced in the renormalized hhhhhh coupling constant when the additional particles show the non-decoupling property. Therefore, even in the case where the hZZhZZ coupling is close to the SM value, deviation in the hhhhhh coupling from the SM value can become as large as plus 100 percent, while that in the hZZhZZ coupling is at most minus 1 percent level. Such large quantum effect on the Higgs tri-linear coupling is distinguishable from the tree level mixing effect, and is expected to be detectable at a future linear collider.Comment: 52 pages, 10 figures, revtex

    Inverse seesaw and dark matter in models with exotic lepton triplets

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    We show that models with exotic leptons transforming as E ~ (1,3,-1) under the standard model gauge symmetry are well suited for generating neutrino mass via a radiative inverse seesaw. This approach realizes natural neutrino masses and allows multiple new states to appear at the TeV scale. The exotic leptons are therefore good candidates for new physics that can be probed at the LHC. Furthermore, remnant low-energy symmetries ensure a stable dark matter candidate, providing a link between dark matter and the origins of neutrino mass.Comment: 6 pages, 3 figures (revtex4.1, two-columns

    MSMC and MSMC2: the multiple sequentially markovian coalescent

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    The Multiple Sequentially Markovian Coalescent (MSMC) is a population genetic method and software for inferring demographic history and population structure through time from genome sequences. Here we describe the main program MSMC and its successor MSMC2. We go through all the necessary steps of processing genomic data from BAM files all the way to generating plots of inferred population size and separation histories. Some background on the methodology itself is provided, as well as bash scripts and python source code to run the necessary programs. The reader is also referred to community resources such as a mailing list and github repositories for further advice

    Muon Anomalous Magnetic Moment and mu -> e gamma in B-L Model with Inverse Seesaw

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    We study the anomalous magnetic moment of the muon, a_\mu, and lepton flavor violating decay \mu -> e \gamma in TeV scale B-L extension of the Standard Model (SM) with inverse seesaw mechanism. We show that the B-L contributions to a_\mu are severely constrained, therefore the SM contribution remains intact. We also emphasize that the current experimental limit of BR(\mu -> e \gamma) can be satisfied for a wide range of parameter space and it can be within the reach of MEG experiment.Comment: 10 pages, 4 Figure

    The Little Review on Leptogenesis

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    This is a brief review on the scenario of baryogenesis through leptogenesis. Leptogenesis is an appealing scenario that may relate the observed baryon asymmetry in the Universe to the low-energy neutrino data. In this review talk, particular emphasis is put on recent developments on the field, such as the flavourdynamics of leptogenesis and resonant leptogenesis near the electroweak phase transition. It is illustrated how these recent developments enable the modelling of phenomenologically predictive scenarios that can directly be tested at the LHC and indirectly in low-energy experiments of lepton-number and lepton-flavour violation.Comment: 15 pages, based on a plenary presentation given at the DISCRETE'08 Symposium, 11-16 December 2008, Valencia, Spai

    Proposal for generalised Supersymmetry Les Houches Accord for see-saw models and PDG numbering scheme

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    The SUSY Les Houches Accord (SLHA) 2 extended the first SLHA to include various generalisations of the Minimal Supersymmetric Standard Model (MSSM) as well as its simplest next-to-minimal version. Here, we propose further extensions to it, to include the most general and well-established see-saw descriptions (types I/II/III, inverse, and linear) in both an effective and a simple gauged extension of the MSSM framework. In addition, we generalise the PDG numbering scheme to reflect the properties of the particles.Comment: 44 pages. Changed titl

    Non-standard interactions versus non-unitary lepton flavor mixing at a neutrino factory

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    The impact of heavy mediators on neutrino oscillations is typically described by non-standard four-fermion interactions (NSIs) or non-unitarity (NU). We focus on leptonic dimension-six effective operators which do not produce charged lepton flavor violation. These operators lead to particular correlations among neutrino production, propagation, and detection non-standard effects. We point out that these NSIs and NU phenomenologically lead, in fact, to very similar effects for a neutrino factory, for completely different fundamental reasons. We discuss how the parameters and probabilities are related in this case, and compare the sensitivities. We demonstrate that the NSIs and NU can, in principle, be distinguished for large enough effects at the example of non-standard effects in the μ\mu-τ\tau-sector, which basically corresponds to differentiating between scalars and fermions as heavy mediators as leading order effect. However, we find that a near detector at superbeams could provide very synergistic information, since the correlation between source and matter NSIs is broken for hadronic neutrino production, while NU is a fundamental effect present at any experiment.Comment: 32 pages, 5 figures. Final version published in JHEP. v3: Typo in Eq. (27) correcte

    Sensitivity of Localized Surface Plasmon Resonances to Bulk and Local Changes in the Optical Environment

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    This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry C copyright © 2009 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/jp810322qSingle rod-shaped and disk-shaped gold nanoparticles with sizes ranging from 60 to 162 nm were analyzed using dark-field scattering spectroscopy. The sensitivity of the localized surface plasmon resonance (LSPR) of each nanoparticle to both a bulk and a local change in the refractive index of the environment was obtained by monitoring the change in the spectral position of the LSPR. It was found that the rods were more sensitive to changes in both the local environment and the bulk environment, in particular rods with a length > 110 nm. This behavior was confirmed by finite element modeling of the structures that clearly indicated a saturation of the relative wavelength shift for the disks as the diameter increased whereas the sensitivity of the rods continued to increase linearly with increasing length. This disparity in the behavior of the two types of nanoparticle may in part be attributed to two principal effects associated with the presence of the substrate: first, that the proportion of the surface area of the nanoparticle in contact with the substrate is larger for the disk than for the rod; second, that the LSPR electromagnetic field is more concentrated within the superstrate for the rod compared to the disk. Further analysis of data obtained from modeling a changing local environment indicates that, although the rods are more sensitive, both rods and disks exhibit a similar field confinement
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