7,893 research outputs found
D Branes and Textures
We examine the flavor structure of the trilinear superpotential couplings
which can result from embedding the Standard Model within D brane sectors in
Type IIB orientifold models, which are examples within the Type I string
framework. We find in general that the allowed flavor structures of the Yukawa
coupling matrices to leading order are given by basic variations on the
"democratic" texture ansatz. In certain interesting cases, the Yukawa couplings
have a novel structure in which a single right-handed fermion couples
democratically at leading order to three left-handed fermions. We discuss the
viability of such a ``single right-handed democracy'' in detail; remarkably,
even though there are large mixing angles in the u,d sectors separately, the
CKM mixing angles are small. The analysis demonstrates the ways in which the
Type I superstring framework can provide a rich setting for investigating novel
resolutions to the flavor puzzle.Comment: 23 pages, references adde
Limits on violations of Lorentz Symmetry from Gravity Probe B
Generic violations of Lorentz symmetry can be described by an effective field
theory framework that contains both general relativity and the standard model
of particle physics called the Standard-Model Extension (SME). We obtain new
constraints on the gravitational sector of the SME using recently published
final results from Gravity Probe B. These include for the first time an upper
limit at the 10^(-3) level on the time-time component of the new tensor field
responsible for inducing local Lorentz violation in the theory, and an
independent limit at the 10^(-7) level on a combination of components of this
tensor field.Comment: 8 pages, 1 figur
Toward understanding the Soviet Union
Thesis (M.A.)--Boston University, 1947. This item was digitized by the Internet Archive
Evaluation of the suitability of Skylab data for the purpose of petroleum exploration
There are no author-identified significant results in this report
Phenomenological Implications of Supersymmetric Family Non-universal U(1)-prime Models
We construct a class of anomaly-free supersymmetric U(1)' models that are
characterized by family non-universal U(1)' charges motivated from E_6
embeddings. The family non-universality arises from an interchange of the
standard roles of the two SU(5) 5* representations within the 27 of E_6 for the
third generation. We analyze U(1)' and electroweak symmetry breaking and
present the particle mass spectrum. The models, which include additional Higgs
multiplets and exotic quarks at the TeV scale, result in specific patterns of
flavor-changing neutral currents in the b to s transitions that can accommodate
the presently observed deviations inthis sector from the SM predictions.Comment: 25 pages, 3 figure
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