2,656 research outputs found

    New Physics Effects in Higgs Decay to Tau Leptons

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    We study the possible effects of TeV scale new physics (NP) on the rate for Higgs boson decays to charged leptons, focusing on the tau tau channel which can be readily studied at the Large Hadron collider. Using an SU(3)_C X SU(2)_L X U(1)_Y invariant effective theory valid below a NP scale Lambda, we determine all effective operators up to dimension six that could generate appreciable contributions to the decay rate and compute the dependence of the rate on the corresponding operator coefficients. We bound the size of these operator coefficients based on the scale of the tau mass, naturalness considerations, and experimental constraints on the tau anomalous magnetic moment. These considerations imply that contributions to the decay rate from a NP scale Lambda ~ TeV could be comparable to the prediction based on the SM Yukawa interaction. A reliable test of the Higgs mechanism for fermion mass generation via the h-> tau tau channel is possible only after such NP effects are understood and brought under theoretical control.Comment: 10 pages, 6 figures, V2: typos correcte

    First Glimpses at Higgs' face

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    The 8 TeV LHC Higgs search data just released indicates the existence of a scalar resonance with mass ~ 125 GeV. We examine the implications of the data reported by ATLAS, CMS and the Tevatron collaborations on understanding the properties of this scalar by performing joint fits on its couplings to other Standard Model particles. We discuss and characterize to what degree this resonance has the properties of the Standard Model (SM) Higgs, and consider what implications can be extracted for New Physics in a (mostly) model-independent fashion. We find that, if the Higgs couplings to fermions and weak vector bosons are allowed to differ from their standard values, the SM is ~ 2 sigma from the best fit point to current data. Fitting to a possible invisible decay branching ratio, we find BR_{inv} = 0.05\pm 0.32\ (95% C.L.) We also discuss and develop some ways of using the data in order to bound or rule out models which modify significantly the properties of this scalar resonance and apply these techniques to the global current data set.Comment: 26 pages, 7 figures, v2 post ICHEP data updat

    Jets in Effective Theory: Summing Phase Space Logs

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    We demonstrate how to resum phase space logarithms in the Sterman-Weinberg (SW) dijet decay rate within the context of Soft Collinear Effective theory (SCET). An operator basis corresponding to two and three jet events is defined in SCET and renormalized. We obtain the RGE of the two and three jet operators and run the operators from the scale μ2=Q2\mu^2 = Q^2 to the phase space scale μδ2=δ2Q2 \mu^2_\delta = \delta^2 Q^2. This phase space scale, where δ\delta is the cone half angle of the jet, defines the angular region of the jet. At μδ2 \mu^2_{\delta} we determine the mixing of the three and two jet operators. We combine these results with the running of the two jet shape function, which we run down to an energy cut scale μβ2\mu^2_{\beta}. This defines the resumed SW dijet decay rate in the context of SCET. The approach outlined here demonstrates how to establish a jet definition in the context of SCET. This allows a program of systematically improving the theoretical precision of jet phenomenology to be carried out.Comment: 25 pages, 4 figures, V2: Typos fixed, writing clarified, detail on PSRG added. Matching onto jet definition changed to taking place at collinear scal

    Asymptotic safety of scalar field theories

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    We study 3d O(N)symmetric scalar field theories using Polchinski's renormalisation group. In the infinite N limit the model is solved exactly including at strong coupling. At short distances the theory is described by a line of asymptotically safe ultraviolet fixed points bounded by asymptotic freedom at weak, and the Bardeen-Moshe-Bander phenomenon at strong sextic coupling. The Wilson-Fisher fixed point arises as an isolated low-energy fixed point. Further results include the conformal window for asymptotic safety, convergence-limiting poles in the complex field plane, and the phase diagram with regions of first and second order phase transitions. We substantiate a duality between Polchinski's and Wetterich's versions of the functional renormalisation group, also showing that that eigenperturbations are identical at any fixed point. At a critical sextic coupling, the duality is worked out in detail to explain the spontaneous breaking of scale symmetry responsible for the generation of a light dilaton. Implications for asymptotic safety in other theories are indicated

    Coordinating Expertise to Preserve and Increase Discoverability of Key University of Tennessee Agricultural Serials

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    This article describes a successful collaborative effort between a branch and the main campus library at the University of Tennessee (UT), Knoxville, to digitize agricultural serials. Experts in agricultural content, preservation, digitization, and metadata worked to preserve three agricultural print publications and make approximately 3,800 issues discoverable for patrons on campus and beyond. This discussion provides a background to Extension and the Experiment Station in Tennessee, outlines previous attempts made to digitize agricultural serials at UT Libraries, and details decisions made during the digitization process and metadata creation. These experiences offer a model for other libraries pursuing similar digitization projects
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