841 research outputs found

    Top triangle moose: Combining Higgsless and topcolor mechanisms for mass generation

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    We present the details of a deconstructed model that incorporates both Higgsless and top-color mechanisms. The model alleviates the tension between obtaining the correct top quark mass and keeping Δρ small that exists in many Higgsless models. It does so by singling out the top quark mass generation as arising from a Yukawa coupling to an effective top Higgs which develops a small vacuum expectation value, while electroweak symmetry breaking results largely from a Higgsless mechanism. As a result, the heavy partners of the SM fermions can be light enough to be seen at the LHC. After presenting the model, we detail the phenomenology, showing that for a broad range of masses, these heavy fermions are discoverable at the LHC. © 2009 The American Physical Society

    High folic acid consumption leads to pseudo-MTHFR deficiency, altered lipid metabolism, and liver injury in mice.

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    Increased consumption of folic acid is prevalent, leading to concerns about negative consequences. The effects of folic acid on the liver, the primary organ for folate metabolism, are largely unknown. Methylenetetrahydrofolate reductase (MTHFR) provides methyl donors for S-adenosylmethionine (SAM) synthesis and methylation reactions

    Spin and Chirality Effects in Antler-Topology Processes at High Energy e+ee^+e^- Colliders

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    We perform a model-independent investigation of spin and chirality correlation effects in the antler-topology processes e+eP+P(+D0)(Dˉ0)e^+e^-\to\mathcal{P}^+\mathcal{P}^-\to (\ell^+ \mathcal{D}^0) (\ell^-\mathcal{\bar{D}}^0) at high energy e+ee^+e^- colliders with polarized beams. Generally the production process e+eP+Pe^+e^-\to\mathcal{P}^+\mathcal{P}^- can occur not only through the ss-channel exchange of vector bosons, V0\mathcal{V}^0, including the neutral Standard Model (SM) gauge bosons, γ\gamma and ZZ, but also through the ss- and tt-channel exchanges of new neutral states, S0\mathcal{S}^0 and T0\mathcal{T}^0, and the uu-channel exchange of new doubly-charged states, U\mathcal{U}^{--}. The general set of (non-chiral) three-point couplings of the new particles and leptons allowed in a renormalizable quantum field theory is considered. The general spin and chirality analysis is based on the threshold behavior of the excitation curves for P+P\mathcal{P}^+\mathcal{P}^- pair production in e+ee^+e^- collisions with longitudinal and transverse polarized beams, the angular distributions in the production process and also the production-decay angular correlations. In the first step, we present the observables in the helicity formalism. Subsequently, we show how a set of observables can be designed for determining the spins and chiral structures of the new particles without any model assumptions. Finally, taking into account a typical set of approximately chiral invariant scenarios, we demonstrate how the spin and chirality effects can be probed experimentally at a high energy e+ee^+e^- collider.Comment: 50 pages, 14 figures, 6 tables, matches version published in EPJ

    Dirac Gauginos, Negative Supertraces and Gauge Mediation

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    In an attempt to maximize General Gauge Mediated parameter space, I propose simple models in which gauginos and scalars are generated from disconnected mechanisms. In my models Dirac gauginos are generated through the supersoft mechanism, while independent R-symmetric scalar masses are generated through operators involving non-zero messenger supertrace. I propose several new methods for generating negative messenger supertraces which result in viable positive mass squareds for MSSM scalars. The resultant spectra are novel, compressed and may contain light fermionic SM adjoint fields.Comment: 16 pages 3 figure

    Momentum asymmetries as CP violating observables

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    Three body decays can exhibit CP violation that arises from interfering diagrams with different orderings of the final state particles. We construct several momentum asymmetry observables that are accessible in a hadron collider environment where some of the final state particles are not reconstructed and not all the kinematic information can be extracted. We discuss the complications that arise from the different possible production mechanisms of the decaying particle. Examples involving heavy neutralino decays in supersymmetric theories and heavy Majorana neutrino decays in Type-I seesaw models are examined.Comment: 20 pages, 9 figures. Clarifying comments and one reference added, matches published versio

    The Universal Real Projective Plane: LHC phenomenology at one Loop

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    The Real Projective Plane is the lowest dimensional orbifold which, when combined with the usual Minkowski space-time, gives rise to a unique model in six flat dimensions possessing an exact Kaluza Klein (KK) parity as a relic symmetry of the broken six dimensional Lorentz group. As a consequence of this property, any model formulated on this background will include a stable Dark Matter candidate. Loop corrections play a crucial role because they remove mass degeneracy in the tiers of KK modes and induce new couplings which mediate decays. We study the full one loop structure of the corrections by means of counter-terms localised on the two singular points. As an application, the phenomenology of the (2,0) and (0,2) tiers is discussed at the LHC. We identify promising signatures with single and di-lepton, top antitop and 4 tops: in the dilepton channel, present data from CMS and ATLAS may already exclude KK masses up to 250 GeV, while by next year they may cover the whole mass range preferred by WMAP data.Comment: 45 pages, 3 figure

    Discovering the composite Higgs through the decay of a heavy fermion

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    A possible composite nature of the Higgs could be revealed at the early stage of the LHC, by analyzing the channels where the Higgs is produced from the decay of a heavy fermion. The Higgs production from a singly-produced heavy bottom, in particular, proves to be a promising channel. For a value \lambda=3 of the Higgs coupling to a heavy bottom, for example, we find that, considering a 125 GeV Higgs which decays into a pair of b-quarks, a discovery is possible at the 8 TeV LHC with 30 fb^{-1} if the heavy bottom is lighter than roughly 530 GeV (while an observation is possible for heavy bottom masses up to 650 GeV). Such a relatively light heavy bottom is realistic in composite Higgs models of the type considered and, up to now, experimentally allowed. At \sqrt{s}=14 TeV the LHC sensitivity on the channel increases significantly. With \lambda=3 a discovery can occur, with 100 fb^{-1}, for heavy bottom masses up to 1040 GeV. In the case the heavy bottom was as light as 500 GeV, the 14 TeV LHC would be sensitive to the measure of the \lambda\ coupling in basically the full range \lambda>1 predicted by the theory.Comment: 25 pp. v2: Minor changes. v3: Version accepted for publication in JHEP. v4: typos fixe

    Logarithmic Corrections to Schwarzschild and Other Non-extremal Black Hole Entropy in Different Dimensions

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    Euclidean gravity method has been successful in computing logarithmic corrections to extremal black hole entropy in terms of low energy data, and gives results in perfect agreement with the microscopic results in string theory. Motivated by this success we apply Euclidean gravity to compute logarithmic corrections to the entropy of various non-extremal black holes in different dimensions, taking special care of integration over the zero modes and keeping track of the ensemble in which the computation is done. These results provide strong constraint on any ultraviolet completion of the theory if the latter is able to give an independent computation of the entropy of non-extremal black holes from microscopic description. For Schwarzschild black holes in four space-time dimensions the macroscopic result seems to disagree with the existing result in loop quantum gravity.Comment: LaTeX, 40 pages; corrected small typos and added reference

    RECAST: Extending the Impact of Existing Analyses

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    Searches for new physics by experimental collaborations represent a significant investment in time and resources. Often these searches are sensitive to a broader class of models than they were originally designed to test. We aim to extend the impact of existing searches through a technique we call 'recasting'. After considering several examples, which illustrate the issues and subtleties involved, we present RECAST, a framework designed to facilitate the usage of this technique.Comment: 13 pages, 4 figure
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