1,945 research outputs found
Multi-Messenger Theories of Gauge-Mediated Supersymmetry Breaking
We study gauge-mediated theories containing several messengers with the most
general SU(5)-invariant mass and supersymmetry-breaking parameters. We show
that these theories are predictive, containing only two relevant parameters
more than the minimal gauge-mediated model. Hypercharge D-terms can contribute
significantly to the right-handed charged sleptons and bring them closer in
mass to the left-handed sleptons. The messenger masses must be invariant under
either SU(5) or a ``messenger parity" to avoid spontaneous breaking of charge
conservation.Comment: 13 pages, 2 figure
Implications of Low Energy Supersymmetry Breaking at the Tevatron
The signatures for low energy supersymmetry breaking at the Tevatron are
investigated. It is natural that the lightest standard model superpartner is an
electroweak neutralino, which decays to an essentially massless Goldstino and
photon, possibly within the detector. In the simplest models of gauge-mediated
supersymmetry breaking, the production of right-handed sleptons, neutralinos,
and charginos leads to a pair of hard photons accompanied by leptons and/or
jets with missing transverse energy. The relatively hard leptons and softer
photons of the single e^+e^- \gamma \gamma + \EmissT event observed by CDF
implies this event is best interpreted as arising from left-handed slepton pair
production. In this case the rates for l^{\pm} \gamma \gamma + \EmissT and
\gamma \gamma + \EmissT are comparable to that for l^+l^- \gamma \gamma +
\EmissT.Comment: 18 pages, Latex, tables correcte
Dark Matter in Theories of Gauge-Mediated Supersymmetry Breaking
In gauge-mediated theories supersymmetry breaking originates in a strongly
interacting sector and is communicated to the ordinary sparticles via
SU(3)SU(2)U(1) carrying ``messenger'' particles. Stable baryons
of the strongly interacting supersymmetry breaking sector naturally weigh
100 TeV and are viable cold dark matter candidates. They interact too
weakly to be observed in dark matter detectors. The lightest messenger particle
is a viable cold dark matter candidate under particular assumptions. It weighs
less than 5 TeV, has zero spin and is easily observable in dark matter
detectors.Comment: 10 pages, Late
Renormalization in General Gauge Mediation
We revisit General Gauge Mediation (GGM) in light of the supersymmetric
(linear) sigma model by utilizing the current superfield. The current
superfield in the GGM is identified with supersymmetric extension of the vector
symmetry current of the sigma model while spontaneous breakdown of
supersymmetry in the GGM corresponds to soft breakdown of the axial vector
symmetry of the sigma model. We first derive the current superfield from the
supersymmetric linear sigma model and then compute 2-point functions of the
current superfield using the (anti-)commutation relations of the messenger
component fields. After the global symmetry are weakly gauged, the 2-point
functions of the current superfield are identified with a part of the 2-point
functions of the associated vector superfield. We renormalize them by
dimensional regularization and show that physical gaugino and sfermion masses
of the MSSM are expressed in terms of the wavefunction renormalization
constants of the component fields of the vector superfield.Comment: 25 pages, 12 figure
Symmetric Points in the Landscape as Cosmological Attractors
In the landscape, if there is to be any prospect of scientific prediction, it
is crucial that there be states which are distinguished in some way. The
obvious candidates are states which exhibit symmetries. Here we focus on states
which exhibit discrete symmetries. Such states are rare, but one can speculate
that they are cosmological attractors. We investigate the problem in model
landscapes and cosmologies which capture some of the features of candidate flux
landscapes. In non-supersymmetric theories we find no evidence that such states
might be cosmologically favored. In supersymmetric theories, simple arguments
suggest that states which exhibit symmetries might be. Our considerations
lead us to raise questions about some popular models of eternal inflation.Comment: 27 pages, latex, minor typo correcte
Propagation of supersymmetric charged sleptons at high energies
The potential for neutrino telescopes to discover charged stau production in
neutrino-nucleon interactions in Earth depends in part on the stau lifetime and
range. In some supersymmetric scenarios, the next lightest supersymmetric
particle is a stau with a decay length on the scale of 10 km. We evaluate the
electromagnetic energy loss as a function of energy and stau mass. The energy
loss parameter scales as the inverse stau mass for the dominating
electromagnetic processes, photonuclear and pair production. The range
can be parameterized as a function of stau mass, initial energy and minimum
final energy. In comparison to earlier estimates of the stau range, our results
are as much as a factor of two larger, improving the potential for stau
discovery in neutrino telescopes.Comment: 7 pages, 8 figures, version accepted for publication in Astroparticle
Physic
On Flux Compactification and Moduli Stabilization
We study the effect of adding charged matter fields to both D3 and D7 branes
in type IIB string theory compactification with fluxes. Generically, charged
matter fields induce additional terms to the Kahler form, the superpotential
and the D-terms. These terms allow for minima with positive or zero
cosmological constants, even in the absence of non-perturbative effects. We
show this result first by decoupling the dilaton field along the lines of the
KKLT, and second by reincorporating it in the action with the Kahler moduli.Comment: 9 page
Remarks on the Racetrack Scheme
There are only a small number of ideas for stabilizing the moduli of string
theory. One of the most appealing of these is the racetrack mechanism, in which
a delicate interplay between two strongly interacting gauge groups fixes the
value of the coupling constant. In this note, we explore this scenario. We find
that quite generally, some number of discrete tunings are required in order
that the mechanism yield a small gauge coupling. Even then, there is no sense
in which a weak coupling approximation is valid. On the other hand, certain
holomorphic quantities can be computed, so such a scheme is in principle
predictive. Searching for models which realize this mechanism is thus of great
interest. We also remark on cosmology in these schemes.Comment: 20 pp, latex, discussion of calculability modifie
Supersymmetry Breaking in the Early Universe
Supersymmetry breaking in the early universe induces scalar soft potentials
with curvature of order the Hubble constant. This has a dramatic effect on the
coherent production of scalar fields along flat directions. For the moduli
problem it generically gives a concrete realization of the problem by
determining the field value subsequent to inflation. However it might suggest a
solution if the minimum of the induced potential coincides with the true
minimum. The induced Hubble scale mass also has important implications for the
Affleck-Dine mechanism of baryogenesis. This mechanism requires large squark or
slepton expectation values to develop along flat directions in the early
universe. This is generally not the case if the induced mass squared is
positive, but does occur if it is negative. The resulting baryon to entropy
ratio depends mainly on the dimension of the nonrenormalizable operator in the
superpotential which stabilizes the flat direction, and the reheat temperature
after inflation. Unlike the original scenario, it is possible to obtain an
acceptable baryon asymmetry without subsequent entropy releases.Comment: 11 pages, requires phyzz
A Model of Direct Gauge Mediation
We present a simple model of gauge mediation (GM) which does not have a
messenger sector or gauge singlet fields. The standard model gauge groups
couple directly to the sector which breaks supersymmetry dynamically. This is
the first phenomenologically viable example of this type in the literature.
Despite the direct coupling, the model can preserve perturbative gauge
unification. This is achieved by the inverted hierarchy mechanism which
generates a large scalar expectation value compared to the size of
supersymmetry breaking. There is no dangerous negative contribution to the
squark, slepton masses due to two-loop renormalization group equation. The
potentially non-universal supergravity contribution to the scalar masses can be
suppressed enough to maintain the virtue of the gauge mediation. The model is
completely chiral, and one does not need to forbid mass terms for the messenger
fields by hand. Beyond the simplicity of the model, it possesses cosmologically
desirable features compared to the original models of GM: an improved gravitino
and string moduli cosmology. The Polonyi problem is back unlike in the original
GM models, but is still much less serious than in hidden sector models.Comment: LaTeX, 12 page
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