40 research outputs found
Dicyclic Horizontal Symmetry and Supersymmetric Grand Unification
It is shown how to use as horizontal symmetry the dicyclic group in a supersymmetric unification where
one acts on the first and second families, in a horizontal doublet, and
the other acts on the third. This can lead to acceptable quark masses and
mixings, with an economic choice of matter supermultiplets, and charged lepton
masses can be accommodated.Comment: 10 pages, LaTe
Bilinear R-parity violation with flavor symmetry
Bilinear R-parity violation (BRPV) provides the simplest intrinsically
supersymmetric neutrino mass generation scheme. While neutrino mixing
parameters can be probed in high energy accelerators, they are unfortunately
not predicted by the theory. Here we propose a model based on the discrete
flavor symmetry with a single R-parity violating parameter, leading to
(i) correct Cabbibo mixing given by the Gatto-Sartori-Tonin formula, and a
successful unification-like b-tau mass relation, and (ii) a correlation between
the lepton mixing angles and in agreement with
recent neutrino oscillation data, as well as a (nearly) massless neutrino,
leading to absence of neutrinoless double beta decay.Comment: 16 pages, 3 figures. Extended version, as published in JHE
REALISTIC MODELS WITH A LIGHT U(1) GAUGE BOSON COUPLED TO BARYON NUMBER
We recently showed that a new gauge boson coupling only to baryon
number is phenomenologically allowed, even if and . In our previous work we assumed that kinetic mixing between the baryon
number and hypercharge gauge bosons (via an term)
was small enough to evade constraints from precision electroweak measurements.
In this paper we propose a class of models in which this term is naturally
absent above the electroweak scale. We show that the generation of a mixing
term through radiative corrections in the low-energy effective theory does not
lead to conflict with precision electroweak measurements and may provide a
leptonic signal for models of this type at an upgraded Tevatron.Comment: 21 pages, LaTeX, 4 figures in a uuencoded compressed postscript file
A Supersymmetric Theory of Flavor and R Parity
We construct a renormalizable, supersymmetric theory of flavor and parity
based on the discrete flavor group . The model can account for all the
masses and mixing angles of the Standard Model, while maintaining sufficient
squark degeneracy to circumvent the supersymmetric flavor problem. By starting
with a simpler set of flavor symmetry breaking fields than we have suggested
previously, we construct an economical Froggatt-Nielsen sector that generates
the desired elements of the fermion Yukawa matrices. With the particle content
above the flavor scale completely specified, we show that all renormalizable
-parity-violating interactions involving the ordinary matter fields are
forbidden by the flavor symmetry. Thus, parity arises as an accidental
symmetry in our model. Planck-suppressed operators that violate parity, if
present, can be rendered harmless by taking the flavor scale to be GeV.Comment: 28 pp. LaTeX, 1 Postscript Figur
Fermion Electric Dipole Moments in Supersymmetric Models with R-parity Violation
We analyze the electron and neutron electric dipole moments induced by
R-parity violating interactions in supersymmetric models. It is pointed out
that dominant contributions can come from one-loop diagrams involving both the
bilinear and trilinear R-parity odd couplings, leading to somewhat severe
constraints on the products of those couplings.Comment: Revtex, 19pp, four figures in axodraw.st
Supersymmetric Froggatt-Nielsen Models with Baryon- and Lepton-Number Violation
We systematically investigate the embedding of U(1)_X Froggatt-Nielsen models
in (four-dimensional) local supersymmetry. We restrict ourselves to models with
a single flavon field. We do not impose a discrete symmetry by hand, e.g.
R-parity, baryon-parity or lepton-parity. Thus we determine the order of
magnitude of the baryon- and/or lepton violating coupling constants through the
Froggatt-Nielsen mechanism. We then scrutinize whether the predicted coupling
constants are in accord with weak or GUT scale constraints. Many models turn
out to be incompatible.Comment: Final version, references added, minor corrections; LaTeX, 46 page
Predictions from an Anomalous U(1) Model of Yukawa Hierarchies
We present a supersymmetric standard model with three gauged Abelian
symmetries, of a type commonly found in superstrings. One is anomalous, the
other two are family symmetries. It has a vacuum in which only these
symmetries are broken by stringy effects. It reproduces all observed quark and
charged lepton Yukawa hierarchies, and the value of the Weinberg angle. It
predicts three massive neutrinos, with mixing that can explain both the small
angle MSW effect, and the atmospheric neutrino anomaly. The Cabibbo angle is
expressed in terms of the gauge couplings at unification. It conserves
R-parity, and proton decay is close to experimental bounds.Comment: 26 page
Supersymmetry without R-Parity and without Lepton Number
We investigate Supersymmetric models where neither R parity nor lepton number
is imposed. Neutrino masses can be kept highly suppressed compared to the
electroweak scale if the -terms in the superpotential are aligned with the
SUSY-breaking bilinear -terms. This situation arises naturally in the
framework of horizontal symmetries. The same symmetries suppress the trilinear
R parity violating terms in the superpotential to an acceptable level.Comment: 18 pages, harvma
The Winter Worries of Bats : Past and Present Perspectives on Winter Habitat and Management of Cave Hibernating Bats
Winter is a time of fascinating changes in biology for cave-hibernating bats, but it is also a time of vulnerability. Unsurprisingly, assessments of winter habitat for these mammals and how it can be managed have been a focus of many researchers involved with the North American Society for Bat Research over the last 50 years. Over this time, a paradigm shift has occurred in the way scientists think about factors driving selection of winter habitat, especially temperature. To illustrate this change, we review three hypotheses seeking to explain microclimate selection in cavernicolous bats. The first, which we call the “Colder is Better Hypothesis,” posits that bats should select cold microclimates that minimize energy expenditure. The “Hibernation Optimization Hypothesis” suggests that bats should select microclimates that reduce expression of torpor to balance energy conservation against non-energetic costs of hibernation. Finally, the “Thrifty Female Hypothesis” asserts that females should select colder microclimates than males to conserve energy for reproduction. We discuss these hypotheses and the shift from viewing hibernation as a phenomenon driven solely by the need to conserve energy in the context of hibernacula management in North America. We focus on both historical and recent conservation threats, most notably alteration of thermal regimes and the disease white-nose syndrome. We urge against returning to an over-simplified view of winter habitat selection in response to our current conservation challenges.Peer reviewe
Flavour Structure of R-violating Neutralino Decays at the LHC
We study signatures of R-parity violation in the production of supersymmetric
particles at the LHC, and the subsequent decay of the lightest neutralino being
the end product of a supersymmetric cascade decay. In doing so, we pay
particular attention to the possible flavour structure of the operators, and
how one may discriminate between different possibilities. A neutralino LSP
would couple to all quarks and leptons and a comparative study of its decays
provides an optimal channel for the simultaneous study of all 45 R-violating
operators. By studying the expected signals from all these operators, we
demonstrate the ability to understand whether more than one coupling dominates,
and to map the experimental signatures to operator hierarchies that can then be
compared against theoretical models of flavour. Detailed comparisons with
backgrounds, including those from MSSM cascade decays are made, using the
PYTHIA event simulator.Comment: 47 pages, 22 figures; v2 matches JHEP versio