468 research outputs found
Gravitational Scattering in the ADD-model Revisited
Gravitational scattering in the ADD-model is studied and it is argued that no
cut-off is needed for the exchange of virtual Kaluza--Klein modes. By
introduction of a small coordinate in the extra dimensions a unique form of the
Kaluza--Klein-summed propagator is found for an odd number of extra dimensions.
The matrix element corresponding to this propagator can also (as opposed to the
cut-offed version) be Fourier transformed to position space, giving back the
extra-dimensional version of Newton's law. For an even number of extra
dimensions the propagator is found by requiring that Newton's law should be
recovered
Leptogenesis Scenarios via Non-Thermally Produced Right-handed Neutrino and Sneutrino in Supersymmetric Seesaw Model
We reconsidered leptogenesis scenario from right-handed (s)neutrino produced
by the decay of inflaton. Besides the well-investigated case that the neutrino
decays instantaneously after the production, leptogenesis is possible if
neutrino decays after it dominates the universe. In the latter case,
right-handed (s)neutrino can decay either while it is relativistic or after it
becomes non-relativistic. Especially, the first case has not been discussed
seriously in literatures. Resultant lepton asymmetry and constraints from the
gravitino problem are studied in broad parameter region, including all cases of
this scenario. It is also shown how this leptogenesis scenario depends on the
parameters, the inflaton decay rate (the reheating temperature), the
right-handed neutrino mass, the washout parameter, and the constraint from the
gravitino problem. Leptogenesis from relativistic neutrino decay is interesting
because both thermal and non-thermal gravitino problems can be relaxed.Comment: 17 pages, 6 figure
On the Tuning Condition of Split Supersymmetry
Split Supersymmetry does not attempt to solve the hierarchy problem, but it
assumes a tuning condition for the electroweak scale. We clarify the meaning of
this condition and show how it is related to the underlying parameters. Simple
assumptions on the structure of the soft terms lead to predictions on tan beta
and on the physical Higgs mass.Comment: 9 pages, 6 figures, latex2
Unificaxion
Dark matter, gauge coupling unification, and the strong CP problem find a
common and simple solution (in the absence of naturalness) within axion models.
We show that such solution, even without specifying the details of the model
implementation, makes testable predictions for the experimentally measurable
axion parameters: the axion mass and its coupling to photons.Comment: 16 pages, 5 figure
Supergravity Inflation Free from Harmful Relics
We present a realistic supergravity inflation model which is free from the
overproduction of potentially dangerous relics in cosmology, namely moduli and
gravitinos which can lead to the inconsistencies with the predictions of baryon
asymmetry and nucleosynthesis. The radiative correction turns out to play a
crucial role in our analysis which raises the mass of supersymmetry breaking
field to intermediate scale. We pay a particular attention to the non-thermal
production of gravitinos using the non-minimal Kahler potential we obtained
from loop correction. This non-thermal gravitino production however is
diminished because of the relatively small scale of inflaton mass and small
amplitudes of hidden sector fields.Comment: 10 pages, revtex, 1 eps figure, references added, conclusion section
expande
Gluino decays with heavier scalar superpartners
We compute gluino decay widths in supersymmetric theories with arbitrary
flavor and CP violation angles. Our emphasis is on theories with scalar
superpartner masses heavier than the gluino such that tree-level two-body
decays are not allowed, which is relevant, for example, in split supersymmetry.
We compute gluino decay branching fractions in several specific examples and
show that it is plausible that the only accessible signal of supersymmetry at
the LHC could be four top quarks plus missing energy. We show another example
where the only accessible signal for supersymmetry is two gluon jets plus
missing energy.Comment: 17 pages, 8 figures. Added references and minor typos and errors
corrected (no change in numerical results
PDF and scale uncertainties of various DY distributions in ADD and RS models at hadron colliders
In the extra dimension models of ADD and RS we study the dependence of the
various parton distribution functions on observable of Drell-Yan process to NLO
in QCD at LHC and Tevatron energies. Uncertainties at LHC due to factorisation
scales in going from leading to next-to-leading order in QCD for the various
distributions get reduced by about 2.75 times for a range . Further uncertainties arising from the error on experimental
data are estimated using the MRST parton distribution functions.Comment: 27 pages, 11 figures, the version to appear in European Physical
Journal
Gluino Decays in Split Supersymmetry
We compute the gluino lifetime and branching ratios in Split Supersymmetry.
Using an effective-theory approach, we resum the large logarithmic corrections
controlled by the strong gauge coupling and the top Yukawa coupling. We find
that the resummation of the radiative corrections has a sizeable numerical
impact on the gluino decay width and branching ratios. Finally, we discuss the
gluino decays into gravitino, relevant in models with direct mediation of
supersymmetry breaking.Comment: 21 pages, 6 figure
Large extra dimension effects in Higgs boson production at linear colliders and Higgs factories
In the framework of quantum gravity propagating in large extra dimensions,
the effects of virtual Kaluza-Klein graviton and graviscalar interference with
Higgs boson production amplitudes are computed at linear colliders and Higgs
factories. The interference of the almost-continuous spectrum of the KK
gravitons with the standard model resonant amplitude is finite and predictable
in terms of the fundamental D-dimensional Plank scale M_D and the number of
extra dimensions \delta. We find that, for M_D ~ 1 TeV and \delta=2, effects of
the order of a few percent could be detected for heavy Higgs bosons (m_H>500
GeV) in Higgs production both via WW fusion in e^+e^- colliders and at
\mu^+\mu^- Higgs-boson factories.Comment: 16 pages, 2 figures ; a few comments and references added ; version
to appear in JHE
Decay and Supersymmetry
The inclusive radiative -decay is a sensitive probe of new physics,
especially if related to the virtual exchange of a charged Higgs boson.
Supersymmetric models provide a particularly interesting example. In the limit
of exact supersymmetry, BR()~=~0, due to the vanishing of any
magnetic-moment transition operator. We illustrate the impact of this
constraint for realistic values of the supersymmetry-breaking parameters.Comment: 7 pages, CERN-TH.6830/93 (Minor changes; a comment on the case >1 has been added
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