1,463 research outputs found
Renormalization Group Invariants in the MSSM and Its Extensions
We derive one-loop renormalization group (RG) invariant observables and
analyze their phenomenological implications in the MSSM and its \mu problem
solving extensions, U(1)' model and NMSSM. We show that there exist several RG
invariants in the gauge, Yukawa and soft-breaking sectors of each model. In
general, RG invariants are highly useful for projecting experimental data to
messenger scale, for revealing correlations among the model parameters, and for
probing the mechanism that breaks supersymmetry. The Yukawa couplings and
trilinear soft terms in U(1)' model and NMSSM do not form RG invariants though
there exist approximate invariants in low tan(beta). In the NMSSM, there are no
invariants that contain the Higgs mass-squareds. We provide a comparative
analysis of RG invariants in all three models and analyze their model-building
and phenomenological implications by a number of case studies.Comment: 32 pages, 5 tables; extended previous analysis to include U(1)'
models and NMSSM where a comparative discussion is give
The Phase Structure of Supersymmetric Sp(2N_c) Gauge Theories with an Adjoint
We study the phase structure of N = 1 supersymmetric Sp(2N_c) gauge theories
with 2N_f fundamentals, an adjoint, and vanishing superpotential. Using
a-maximization, we derive analytic expressions for the values of N_f below
which the first several gauge-invariant operators in the chiral ring violate
the unitarity bound and become free fields. In doing so we are able to
explicitly check previous conjectures about the behavior of this theory made by
Luty, Schmaltz, and Terning. We then compare this to an analysis of the first
two 'deconfined' dual descriptions based on the gauge groups Sp(2N_f+2) x
SO(2N_c+5) and Sp(2N_f+2) x SO(4N_f+4) x Sp(2N_c+2), finding precise agreement.
In particular, we find no evidence for non-obvious accidental symmetries or the
appearance of a mixed phase in which one of the dual gauge groups becomes free.Comment: 18 pages, 2 figures; v2: added references to match JHEP versio
Visible Sector Supersymmetry Breaking Revisited
We revisit the possibility of "visible sector" SUSY models: models which are
straightforward renormalizable extensions of the Minimal Supersymmetric
Standard Model (MSSM), where SUSY is broken at tree level. Models of this type
were abandoned twenty years ago due to phenomenological problems, which we
review. We then demonstrate that it is possible to construct simple
phenomenologically viable visible sector SUSY models. Such models are indeed
very constrained, and have some inelegant features. They also have interesting
and distinctive phenomenology. Our models predict light gauginos and very heavy
squarks and sleptons. The squarks and sleptons may not be observable at the
LHC. The LSP is a stable very light gravitino with a significant Higgsino
admixture. The NLSP is mostly Bino. The Higgs boson is naturally heavy. Proton
decay is sufficently and naturally suppressed, even for a cutoff scale as low
as 10^8 GeV. The lightest particle of the O'Raifeartaigh sector (the LOP) is
stable, and is an interesting cold dark matter candidate.Comment: 23 pages, 3 figures, LaTe
Diffusion Enhances Spontaneous Electroweak Baryogenesis
We include the effects of diffusion in the electroweak spontaneous
baryogenesis scenario and show that it can greatly enhance the resultant baryon
density, by as much as a factor of over previous
estimates. Furthermore, the baryon density produced is rather insensitive to
parameters characterizing the first order weak phase transition, such as the
width and propagation velocity of the phase boundary.Comment: 15 pages, uses harvmac and epsf macro
Yukawa Hierarchy Transfer Based on Superconformal Dynamics and Geometrical Realization in String Models
We propose a scenario that leads to hierarchical Yukawa couplings and
degenerate sfermion masses at the same time, in the context of
extra-dimensional models, which can be naturally embedded in a wide class of
string models. The hierarchy of Yukawa couplings and degeneracy of sfermion
masses can be realized thanks to superconformal gauge dynamics. The sfermion
mass degeneracy is guaranteed by taking the superconformal fixed point to be
family independent. In our scenario, the origin of Yukawa hierarchy is
attributed to geometry of compactified dimensions and the consequent volume
dependence of gauge couplings in the superconformal sectors. The difference in
these gauge couplings is dynamically transferred to the hierarchy of the Yukawa
couplings. Thus, our scenario combines a new dynamical approach and the
conventional geometrical approach to the supersymmetric flavor problem.Comment: 12 pages, latex, no figur
Effect of herbicides on growth and nitrogen fixation potential (ARA) of field pea and lentil
Non-Peer Reviewe
Mixed Gauge and Anomaly Mediation From New Physics at 10 TeV
In the context of anomaly-mediated supersymmetry breaking, it is natural for
vectorlike fields and singlets to have supersymmetry breaking masses of order
10 TeV, and therefore act as messengers of supersymmetry breaking. We show that
this can give rise to phenomenologically viable spectra compatible with
perturbative gauge coupling unification. The minimal model interpolates
continuously between pure anomaly mediation and gauge mediation with a
messenger scale of order 10 TeV. It is also possible to have non-minimal models
with more degenerate specta, with some squarks lighter than sleptons. These
models reduce to the MSSM at low energies and incorporate a natural solution of
the mu problem. The minimal model has four continuous parameters and one
discrete parameter (the number of messengers). The LEP Higgs mass bound can be
satisfied in the minimal model by tuning parameters at the GUT scale to one
part in 50.Comment: 17 pages, 4 figure
Growth and nitrogen fixation of field pea and lentil as influenced by herbicides: a three year field study
Non-Peer ReviewedA three-year field study was conducted in the Dark Brown and Black Soil Zones of Saskatchewan to assess the effects of trifluralin (Treflan ), metribuzin (Sencor), MCPB (Tropotox), and sethoxydim (Poast) on growth and symbiotic nitrogen fixation of field pea (Pisum sativum cv. Trapper) and lentil (Lens culinaris cv. Eston). Herbicides were applied at Saskatchewan recommended field rates and twice the recommended field rates. Treflan, Sencor, and Poast did not adversely affect plant growth or nitrogen fixation potential of field pea and lentil when applied at recommended field rates. Similarly, application of MCPB at the recommended rate did not adversely affect field pea under normal growing conditions. In some instances, herbicide application at the recommended rate was observed to have a stimulatory effect on growth and nitrogen fixation. In contrast, at application rates in excess of those currently recommended in Saskatchewan, or when plants were severely stressed by unfavorable growing conditions such as poor soil
moisture, plant growth, yield, nodulation, and nitrogen fixation were adversely effected by herbicides. These effects were not consistent nor were they predictable. MCPB is not registered for use in lentil and,
when applied in this crop, often resulted in reduced nitrogen fixation and seed yield. In all cases, data suggest that reductions in the nitrogen fixation potential were due to indirect effects of herbicide application on plant growth rather than to direct effects on nodulation and nitrogenase activity
Defective Vortex Lattices in Layered Superconductors with Point Pins at the Extreme Type-II Limit
The mixed phase of layered superconductors with no magnetic screening is
studied through a partial duality analysis of the corresponding frustrated XY
model in the presence of weak random point pins. Isolated layers exhibit a
defective vortex lattice at low temperature that is phase coherent.
Sufficiently weak Josephson coupling between adjacent layers results in an
entangled vortex solid that exhibits weak superconductivity across layers. The
corresponding vortex liquid state shows an inverted specific heat anomaly that
we propose accounts for that seen in YBCO. A three-dimensional vortex lattice
with dislocations occurs at stronger coupling. This crossover sheds light on
the apparent discrepancy concerning the observation of a vortex-glass phase in
recent Monte Carlo simulations of the same XY model.Comment: 4 pages, 1 figure. To appear in PRB, rapid communicatio
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