43,854 research outputs found
One-loop stau masses in the effective potential approach
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
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)
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
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 ( 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
, provided the Dirac phase is very close to maximal (). In the case of a normal neutrino mass spectrum, i.e. when , the
agreement of our model with the data is less than optimal---the reactor mixing
angle 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
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