43,088 research outputs found

    One-loop stau masses in the effective potential approach

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    We calculate the one-loop contributions to the tau slepton masses in the Minimal Supersymmetric Standard Model in the effective potential approach. For the majority of parameter space under study, those corrections are shown to elevate the value of the lightest stau mass.Comment: 11 pages, 3 figure

    Generalized CP Invariance and the Yukawa sector of Two-Higgs Models

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    We analyze generalized CP symmetries of two-Higgs doublet models, extending them from the scalar to the fermion sector of the theory. We show that, with a single exception, those symmetries imply massless fermions. The single model which accommodates a fermionic mass spectrum compatible with experimental data possesses a remarkable feature. It displays a new type of spontaneous CP violation, which occurs not in the scalar sector responsible for the symmetry breaking mechanism but, rather, in the fermion sector.Comment: RevTex, 4 pages, no figures Version2: Remarkable additional conclusion => title & text changes; section adde

    Impact of FCNC top quark interactions on BR(t -> b W)

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    We study the effect that FCNC interactions of the top quark will have on the branching ratio of charged decays of the top quark. We have performed an integrated analysis using Tevatron and B-factories data and with just the further assumption that the CKM matrix is unitary we can obtain very restrictive bounds on the strong and electroweak FCNC branching ratios Br(t -> q X) < 4.0 10^{-4}, where X is any vector boson and a sum in q = u,c is implied.Comment: 10 pages, 5 figure

    Texture-zero model for the lepton mass matrices

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    We suggest a simple model, based on the type-I seesaw mechanism, for the lepton mass matrices. The model hinges on an Abelian symmetry which leads to mass matrices with some vanishing matrix elements. The model predicts one massless neutrino and MeÎŒ=0M_{e\mu} = 0 (MM is the effective light-neutrino Majorana mass matrix). We show that these predictions perfectly agree with the present experimental data if the neutrino mass spectrum is inverted, i.e. if m3=0m_3 = 0, provided the Dirac phase ÎŽ\delta is very close to maximal (±π/2\pm \pi / 2). In the case of a normal neutrino mass spectrum, i.e. when m1=0m_1 = 0, the agreement of our model with the data is less than optimal---the reactor mixing angle Ξ13\theta_{13} is too small in our model. Minimal leptogenesis is not an option in our model due to the vanishing elements in the Yukawa-coupling matrices.Comment: 10 pages, 3 figures; version for journal: new fit to data, new plot