43,515 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
Mass for Plasma Photons from Gauge Symmetry Breaking
We derive the effective masses for photons in unmagnetized plasma waves using
a quantum field theory with two vector fields (gauge fields). In order to
properly define the quantum field degrees of freedom we re-derive the classical
wave equations on light-front gauge. This is needed because the usual scalar
potential of electromagnetism is, in quantum field theory, not a physical
degree of freedom that renders negative energy eigenstates. We also consider a
background local fluid metric that allows for a covariant treatment of the
problem. The different masses for the longitudinal (plasmon) and transverse
photons are in our framework due to the local fluid metric. We apply the
mechanism of mass generation by gauge symmetry breaking recently proposed by
the authors by giving a non-trivial vacuum-expectation-value to the second
vector field (gauge field). The Debye length is interpreted as an
effective compactification length and we compute an explicit solution for the
large gauge transformations that correspond to the specific mass eigenvalues
derived here. Using an usual quantum field theory canonical quantization we
obtain the usual results in the literature. Although none of these ingredients
are new to physicist, as far as the authors are aware it is the first time that
such constructions are applied to Plasma Physics. Also we give a physical
interpretation (and realization) for the second vector field in terms of the
plasma background in terms of known physical phenomena.
Addendum: It is given a short proof that equation (10) is wrong, therefore
equations (12-17) are meaningless. The remaining results are correct being
generic derivations for nonmagnetized plasmas derived in a covariant QFT
framework.Comment: v1: 1+6 pages v2: Several discussions rewritten; Abstract rewritten;
References added; v3: includes Addendu
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
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