5,790 research outputs found
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
Tau Polarizations in the Three-body Slepton Decays with Stau as the NLSP
In the gauge-mediated supersymmetry breaking models with scalar tau as the
next-to-lightest supersymmetric particle, a scalar lepton may decay dominantly
into its superpartner, tau lepton, and the lightest scalar tau particle. We
give detailed formulas for the three-body decay amplitudes and the polarization
asymmetry of the outgoing tau lepton . We find that the tau polarizations are
sensitive to the model parameters such as the stau mixing angle, the neutralino
to slepton mass ratio and the neutralino mixing effect.Comment: 13 pages, 5 figures, RevTe
Curvaton Scenario with Affleck-Dine Baryogenesis
We discuss the curvaton scenario with the Affleck-Dine baryogenesis. In this
scenario, non-vanishing baryonic entropy fluctuation may be generated even
without primordial fluctuation of the Affleck-Dine field. Too large entropy
fluctuation is inconsistent with the observations and hence constraints on the
curvaton scenario with the Affleck-Dine baryogenesis are obtained. We calculate
the baryonic entropy fluctuation (as well as other cosmological density
fluctuations) in this case and derive constraints. Implications to some of the
models of the curvaton are also discussed.Comment: 16 pages,2 figure
O(a^2) cutoff effects in lattice Wilson fermion simulations
In this paper we propose to interpret the large discretization artifacts
affecting the neutral pion mass in maximally twisted lattice QCD simulations as
O(a^2) effects whose magnitude is roughly proportional to the modulus square of
the (continuum) matrix element of the pseudoscalar density operator between
vacuum and one-pion state. The numerical size of this quantity is determined by
the dynamical mechanism of spontaneous chiral symmetry breaking and turns out
to be substantially larger than its natural magnitude set by the value of
Lambda_QCD.Comment: 38 pages, 1 figure, 2 table
Curvatons in the minimally supersymmetric standard model
Curvaton is an effectively massless field whose energy density during
inflation is negligible but which later becomes dominant. This is a novel
mechanism to generate the scale invariant perturbations. I discuss the
possibility that the curvaton could be found among the fields of the minimally
supersymmetric standard model (MSSM), which contains a number of flat
directions along which the renormalizable potential vanishes. The requirements
of late domination and the absence of damping of the perturbations pick out
essentially a unique candidate for the MSSM curvaton. One must also require
that inflation takes place in a hidden sector. If the inflaton energy density
can be radiated into extra dimensions, many constraints can be relaxed, and the
simplest flat direction consisting of the Higgses H_u and H_d would provide a
working example of an MSSM curvaton.Comment: 16 pages, 1 Figur
Layered Higgs Phase as a Possible Field Localisation on a Brane
So far it has been found by using lattice techniques that in the anisotropic
five--dimensional Abelian Higgs model, a layered Higgs phase exists in addition
to the expected five--dimensional one. The exploration of the phase diagram has
shown that the two Higgs phases are separated by a phase transition from the
confining phase. This transition is known to be first order. In this paper we
explore the possibility of finding a second order transition point in the
critical line which separates the first order phase transition from the
crossover region. This is shown to be the case only for the four--dimensional
Higgs layered phase whilst the phase transition to the five--dimensional broken
phase remains first order. The layered phase serves as the possible realisation
of four--dimensional spacetime dynamics which is embedded in a
five--dimensional spacetime. These results are due to gauge and scalar field
localisation by confining interactions along the extra fifth direction.Comment: 1+15 pages, 12 figure
Non-Bunch-Davies Initial State Reconciles Chaotic Models with BICEP and Planck
The BICEP2 experiment has announced a signal for primordial gravity waves
with tensor-to-scalar ratio [arXiv:1403.3985]. There
are two ways to reconcile this result with the latest Planck experiment
[arXiv:1303.5082]. One is by assuming that there is a considerable tilt of ,
, with a positive sign, corresponding to a blue tilt for the tensor modes of
order , assuming the Planck experiment best-fit
value for tilt of scalar power spectrum . The other possibility is to
assume that there is a negative running in the scalar spectral index,
which pushes up the upper bound on from up
to in the Planck analysis assuming the existence of a tensor spectrum.
Simple slow-roll models fail to provide such large values for
or negative runnings in [arXiv:1403.3985]. In this note we show that a
non-Bunch-Davies initial state for perturbations can provide a match between
large field chaotic models (like ) with the latest Planck result
[arXiv:1306.4914] and BICEP2 results by accommodating either the blue tilt of
or the negative large running of .Comment: v1:5 pages, double column; v2: 6 pages, double column, the option of
negative running of scalar spectral index and some references were added; v3:
Matched the PLB versio
A More Minimal Messenger Model of Gauge-Mediated Supersymmetry Breaking?
This Letter addresses a provocative question: ``Can the standard electroweak
Higgs doublets and their color-triplet partners be the messengers of a low
energy gauge-mediated SUSY breaking?" Such a possibility does not seem to be
immediately ruled out. If so, it can lead to a very economical scheme with
clear-cut predictions quite distinct from those of the conventional
gauge-mediated scenario. Namely, we get (i) a single light Higgs below the
original SUSY- breaking scale; (ii) tan(beta) = 1; (iii) flavor non-universal,
but automatically flavor-conserving soft scalar masses; (iv) a light colored
scalar with peculiar phenomenology. The familiar mu problem looses its meaning
in this approach.Comment: 10 pages, LATEX, no figure
Particle Production of Vector Fields: Scale Invariance is Attractive
In a model of an Abelian vector boson with a Maxwell kinetic term and non-negative mass-squared it is demonstrated that, under fairly general conditions during inflation, a scale-invariant spectrum of perturbations for the components of a vector field, massive or not, whose kinetic function (and mass) is modulated by the inflaton field is an attractor solution. If the field is massless, or if it remains light until the end of inflation, this attractor solution also generates anisotropic stress, which can render inflation weakly anisotropic. The above two characteristics of the attractor solution can source (independently or combined together) significant statistical anisotropy in the curvature perturbation, which may well be observable in the near future
Sneutrino condensate as a candidate for the hot big bang cosmology
If inflationary paradigm is correct, then it must create conditions for the
hot big bang model with all observed matter, baryons and the seed perturbations
for the structure formation. In this paper we propose a scenario where the
inflaton energy density is dumped into the bulk in a brane world setup, and all
the required physical conditions are created by the right handed neutrino
sector within supersymmetry. The scalar component of the right handed Majorana
neutrino is responsible for generating the scale invariant fluctuations in the
cosmic microwave background radiation, reheating the Universe at a
temperature~ GeV, and finally generating the lepton/baryon
asymmetry, , with no lepton/baryon isocurvature
fluctuations.Comment: 19 pages, 3 figures. Some discussion on neutrino masses and
baryogenesis, and other small changes adde
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