76 research outputs found
TRIPLE-PRODUCT SPIN-MOMENTUM CORRELATIONS IN POLARIZED Z DECAYS TO THREE JETS.
We discuss hard rescattering effects that can be measured using CP-even,
T-odd triple-product observables in polarized decays to three
jets. We show that the standard model contributions, from both QCD and
electroweak rescattering, are very small. Thus these measurements are
potentially sensitive to physics beyond the standard model. We investigate one
such contribution which involves a new gauge boson coupling to baryon number.Comment: 4 pages, LaTeX file. One figure not included available upon request
from [email protected]. Text with encapsulated figures also
available in postscript form by anonymous ftp from
ftp://preprint.slac.stanford.edu/preprints/hep-ph/9503 . Talk given at the
4th International Conference on Physics Beyond the Standard Model, Lake
Tahoe, CA, December 94, by Y. S
Gauge Theories in and Fine-Lattice Deconstruction
The logarithmic energy dependence of gauge couplings in AdS_5 emerges almost
automatically when the theory is deconstructed on a coarse lattice. Here we
study the theory away from the coarse-lattice limit. While we cannot
analytically calculate individual KK masses for a fine lattice, we can
calculate the product of all non-zero masses. This allows us to write down the
gauge coupling at low energies for any lattice-spacing and curvature. As
expected, the leading log behaviour is corrected by power-law contributions,
suppressed by the curvature. We then turn to intermediate energies, and discuss
the gauge coupling and the gauge boson profile in perturbation theory around
the coarse-lattice limit.Comment: 17 pages, 1 figure, typos in listing version of abstract correcte
Deconstruction and Gauge Theories in AdS_5
On a slice of AdS_5, despite having a dimensionful coupling, gauge theories
can exhibit logarithmic dependence on scale. In this paper, we utilize
deconstruction to analyze the scaling behavior of the theory, both above and
below the AdS curvature scale, and shed light on position-dependent
regularizations of the theory. We comment on applications to geometries other
than AdS.Comment: 15 pages, 1 figur
Dynamics Of The Formation Of Carbon Nanotube Serpentines.
Recently, Geblinger et al. [Nat. Nanotechnol. 3, 195 (2008)] reported the experimental realization of carbon nanotube S-like shaped nanostructures, the so-called carbon nanotube serpentines. We report here results from multimillion fully atomistic molecular dynamics simulations of their formation. We consider one-μm-long carbon nanotubes placed on stepped substrates with and without a catalyst nanoparticle on the top free end of the tube. A force is applied to the upper part of the tube during a short period of time and turned off; then the system is set free to evolve in time. Our results show that these conditions are sufficient to form robust serpentines and validates the general features of the falling spaghetti model proposed to explain their formation.11010550
Visible Effects of the Hidden Sector
The renormalization of operators responsible for soft supersymmetry breaking
is usually calculated by starting at some high scale and including only visible
sector interactions in the evolution equations, while ignoring hidden sector
interactions. Here we explain why this is correct only for the most trivial
structures in the hidden sector, and discuss possible implications. This
investigation was prompted by the idea of conformal sequestering. In that
framework hidden sector renormalizations by nearly conformal dynamics are
critical. In the original models of conformal sequestering it was necessary to
impose hidden sector flavor symmetries to achieve the sequestered form. We
present models which can evade this requirement and lead to no-scale or anomaly
mediated boundary conditions; but the necessary structures do not seem generic.
More generally, the ratios of scalar masses to gaugino masses, the -term,
the -term, -terms, and the gravitino mass can be significantly
affected.Comment: 23 pages, no figure
The GUT Scale and Superpartner Masses from Anomaly Mediated Supersymmetry Breaking
We consider models of anomaly-mediated supersymmetry breaking (AMSB) in which
the grand unification (GUT) scale is determined by the vacuum expectation value
of a chiral superfield. If the anomaly-mediated contributions to the potential
are balanced by gravitational-strength interactions, we find a
model-independent prediction for the GUT scale of order . The GUT threshold also affects superpartner masses, and can easily
give rise to realistic predictions if the GUT gauge group is asymptotically
free. We give an explicit example of a model with these features, in which the
doublet-triplet splitting problem is solved. The resulting superpartner
spectrum is very different from that of previously considered AMSB models, with
gaugino masses typically unifying at the GUT scale.Comment: 17 page
Dynamical completions of generalized O'Raifeartaigh models
We present gauge theory completions of Wess-Zumino models admitting
supersymmetry breaking vacua with spontaneously broken R-symmetry. Our models
are simple deformations of generalized ITIY models, a supersymmetric theory
with gauge group Sp(N), N+1 flavors plus singlets, with a modified tree level
superpotential which explicitly breaks (part of) the global symmetry. Depending
on the nature of the deformation, we obtain effective O'Raifeartaigh-like
models whose pseudomoduli space is locally stable in a neighborhood of the
origin of field space, or in a region not including it. Hence, once embedded in
direct gauge mediation scenarios, our models can give low energy spectra with
either suppressed or unsuppressed gaugino mass.Comment: 21 pages, 1 figure; v3: reference adde
Measuring Slepton Masses and Mixings at the LHC
Flavor physics may help us understand theories beyond the standard model. In
the context of supersymmetry, if we can measure the masses and mixings of
sleptons and squarks, we may learn something about supersymmetry and
supersymmetry breaking. Here we consider a hybrid gauge-gravity supersymmetric
model in which the observed masses and mixings of the standard model leptons
are explained by a U(1) x U(1) flavor symmetry. In the supersymmetric sector,
the charged sleptons have reasonably large flavor mixings, and the lightest is
metastable. As a result, supersymmetric events are characterized not by missing
energy, but by heavy metastable charged particles. Many supersymmetric events
are therefore fully reconstructible, and we can reconstruct most of the charged
sleptons by working up the long supersymmetric decay chains. We obtain
promising results for both masses and mixings, and conclude that, given a
favorable model, precise measurements at the LHC may help shed light not only
on new physics, but also on the standard model flavor parameters.Comment: 24 pages; v2: fixed a typo in our computer program that led to some
miscalculated branching ratios, various clarifications and minor
improvements, conclusions unchanged, published versio
Filtering Out Signals of Gauge-Mediated Supersymmetry Breaking: Can We Always Eliminate Conventional Supersymmetric Effects ?
We investigate the signal + missing energy in a high-energy
linear collider, with a view to differentiating between gauge-mediated
supersymmetry breaking and the conventional supersymmetric models. Prima facie,
there is considerable chance of confusion between the two scenarios if the
assumption of gaugino mass unification is relaxed. We show that the use of
polarized electron beams enables one to distinguish between the two schemes in
most cases. There are some regions in the parameter space where this idea does
not work, and we suggest some additional methods of distinction. We also
perform an analysis of some signals in the gauge-mediated model, coming from
the pair production of the second-lightest neutralino.Comment: LaTex, 23 pages including 5 figures. Revised version to be publishd
in Physical Review D. Some minor changes were mad
A One-Scale Model of Dynamical Supersymmetry Breaking
A model of gauge-mediated supersymmetry breaking is constructed in which the
low-energy physics depends on a single dynamical scale. Strong coupling
dynamics of gauge theories plays an important role, in particular through its
effects on beta functions and through confinement. The model does not have
distinct messenger and supersymmetry-breaking sectors. The scale of
supersymmetry breaking is of order 10-100 \TeV, implying that the decay of the
next-to-lightest superpartner into the gravitino is prompt. Superoblique
corrections are enhanced. A Dirac fermion and one complex scalar, in a 10 or
\bar{10} of (global) SU(5), are predicted to be relatively light and to satisfy
certain mass relations with the standard model squarks and sleptons.Comment: 28 pages, uses revtex, h-physrev.bs
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