5,862 research outputs found

    A radiatively improved fermiophobic Higgs boson scenario

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    The naive fermiophobic scenario is unstable under radiative corrections, due to the chiral-symmetry breaking induced by fermion mass terms. In a recent study, the problem of including the radiative corrections has been tackled via an effective field theory approach. The renormalized Yukawa couplings are assumed to vanish at a high energy scale Λ\Lambda, and their values at the electroweak scale are computed via modified Renormalization Group Equations. We show that, in case a fermiophobic Higgs scenario shows up at the LHC, a linear collider program will be needed to accurately measure the radiative Yukawa structure, and consequently constrain the Λ\Lambda scale.Comment: 7 pages, 3 figures, Proceedings of the 2011 International Workshop on Future Linear Colliders (LCWS11), Granada (Spain), 26-30 September 201

    Supersymmetric Models and CP violation in B decays

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    In this talk CP violation in the supersymmetric models, and especially in B-decays is discussed. We review our analysis of the supersymmetric contributions to the mixing CP asymmetries of BϕKSB\to \phi K_S and BηKSB\to \eta^{\prime} K_S processes. Both gluino and chargino exchanges are considered in a model independent way by using the mass insertion approximation method. The QCD factorization method is used, and parametrization of this method in terms of Wilson coefficients is presented in both decay modes. Correlations between the CP asymmetries of these processes and the direct CP asymmetry in bsγb\to s \gamma decay are shown.Comment: 16 pages, 7 figures. Prepared for the proceedings of the 1st GUC workshop on High Energy Physics, Cairo, Jan 9-13, 200

    Looking for anomalous gamma-gamma-H and Z-gamma-H couplings at future linear collider

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    We consider the possibility of studying anomalous contributions to the gamma-gamma-H and Z-gamma-H vertices through the process e-gamma--> e-H at future e-gamma linear colliders, with Sqrt(S)=500-1500 GeV. We make a model independent analysis based on SU(2)xU(1) invariant effective operators of dim=6 added to the standard model lagrangian. We consider a light Higgs boson (mostly decaying in bar(b)-b pairs), and include all the relevant backgrounds. Initial e-beam polarization effects are also analyzed. We find that the process e-gamma--> e-H provides an excellent opportunity to strongly constrain both the CP-even and the CP-odd anomalous contributions to the gamma-gamma-H and Z-gamma-H vertices.Comment: LaTeX, 33 pages, 16 eps figures, extended section

    Experimental Constraints on the Neutralino-Nucleon Cross Section

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    In the light of recent experimental results for the direct detection of dark matter, we analyze in the framework of SUGRA the value of the neutralino-nucleon cross section. We study how this value is modified when the usual assumptions of universal soft terms and GUT scale are relaxed. In particular we consider scenarios with non-universal scalar and gaugino masses and scenarios with intermediate unification scale. We also study superstring constructions with D-branes, where a combination of the above two scenarios arises naturally. In the analysis we take into account the most recent experimental constraints, such as the lower bound on the Higgs mass, the bsγb\to s\gamma branching ratio, and the muon g2g-2.Comment: References added, bsgamma upper bound improved, results unchanged, Talk given at Corfu Summer Institute on Elementary Particle Physics, August 31-September 20, 200

    N=1 Supersymmetric Yang-Mills on the lattice at strong coupling

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    We study N=1 supersymmetric SU(N) Yang-Mills theory on the lattice at strong coupling. Our method is based on the hopping parameter expansion in terms of random walks, resummed for any value of the Wilson parameter r in the small hopping parameter region. Results are given for the mesonic (2-gluino) and fermionic (3-gluino) propagators and spectrum.Comment: Latex file. 43 pages. Minor additional comments, references added, typos corrected. Accepted for publication in Int. J. Mod. Phys.

    Chargino contributions to the CP asymmetry in B -> Phi K(S) decay

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    We perform a model independent analysis of the chargino contributions to the CP asymmetry in B -> Phi K(S) process. We use the mass insertion approximation method generalized by including the possibility of a light right-stop. We find that the dominant effect is given by the contributions of the mass insertions deltaU_LL(32) and deltaU_RL(32) to the Wilson coefficient of the chromomagnetic operator. By considering both these contributions simultaneously, the CP asymmetry in B -> Phi K(S) process is significantly reduced and negative values, which are within the 1-sigma experimental range and satisfy the b -> s gamma constraints, can be obtained.Comment: 14 pages, LaTeX, 3.eps Figure

    Implications of effective axial-vector coupling of gluon for ttˉt\bar{t} spin polarizations at the LHC

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    We analyze the impact of effective axial-vector coupling of the gluon on spin polarization observables in ttˉt\bar{t} pair production at the LHC. Working at leading order in QCD, we compute the ttˉt\bar{t} spin-correlation and left-right spin asymmetry coefficients in the helicity basis in the laboratory frame as functions of the new physics scale Λ\Lambda associated with this coupling. We found that the ttˉt\bar{t} invariant mass dependent asymmetries are more sensitive to the scale Λ\Lambda than the corresponding inclusive ones, in particular when suitable cuts selecting high ttˉt\bar{t} invariant mass regions are imposed. In the context of this scenario, we show that the LHC has potential either to confirm or to rule out the Tevatron FB top asymmetry anomaly by analyzing the ttˉt\bar{t} spin-correlation and left-right polarization asymmetries. On the other hand, stringent lower bound on the new physics scale Λ\Lambda can be set in this scenario if no significant deviations from the SM predictions for those observables will be measured.Comment: 26 pages, 8 figures, same as published version in PRD. Few modifications in the text and one new reference adde

    N=1 Super-Yang-Mills on the Lattice: Weak and Strong Coupling Limits

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    We present a general review about the N=1 supersymmetric SU(Nc) Yang-Mills on the lattice focusing our attention on the quenched approximation in supersymmetry. Finally we analyse and discuss the recent results obtained at strong coupling and large Nc for the mesonic and fermionic propagators and spectrum

    On the B -> X_s l^+ l^- decays in general supersymmetric models

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    We analyze the inclusive semileptonic decays B -> X_s l^+ l^- in the framework of the supersymmetric standard model with non-universal soft-breaking terms at GUT scale. We show that the general trend of universal and non-universal models is a decreasing of branching ratio (BR) and increasing of energy asymmetry (AS). However, only non--universal models can have chances to get very large enhancements in BR and AS, corresponding to large (negative) SUSY contributions to the b -> s \gamma amplitude.Comment: 13 pages, 3 figures. References added. To appear in Phys. Lett.
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