376 research outputs found

### Probe of SUSY and Extra Dimensions by the Brookhaven g-2 Experiment

A brief review is given of $a_{\mu}=(g_{\mu}-2)/2$ as a probe of
supersymmetry and of extra dimensions. It is known since the early to mid
nineteen eightees that the supersymmetric electro-weak correction to $a_{\mu}$
can be as large or larger than the Standard Model electro-weak correction and
thus any experiment that proposes to test the Standard Model electro-weak
correction will also test the supersymmetric correction and constrain
supersymmetric models. The new physics effect seen in the Brookhaven (BNL)
experiment is consistent with these early expectations. Detailed analyses
within the well motivated supergravity unified model show that the size of the
observed difference ($a_{\mu}^{exp}-a_{\mu}^{SM}$) seen at Brookhaven implies
upper limits on sparticle masses in a mass range accessible to the direct
observation of these particles at the Large Hadron Collider. Further, analyses
also show that the BNL data is favorable for the detection of supersymmeteric
dark matter in direct dark matter searches. The effect of large extra
dimensions on $a_{\mu}$ is also discussed. It is shown that with the current
limits on the size of extra dimensions, which imply that the inverse size of
such dimensions lies in the TeV region, their effects on $a_{\mu}$ relative to
the supersymmetric contribution is small and thus extra dimensions do not
produce a serious background to the supersymmetric contribution. It is
concluded that the analysis of the additional data currently underway at
Brookhaven as well as a reduction of the hadronic error will help pin down the
scale of weak scale supersymmetry even more precisely.Comment: 11 pages,Latex.Invited talk at La Thuile,01 conference March
4-10,200

### Dark Matter in SUGRA, Strings and Branes

A brief review is given of dark matter in SUGRA, strings and branes. For
SUGRA models the implications of Yukawa coupling unification on dark matter are
discussed in the light of $g-2$ and $b\to s\gamma$ constraints. A brief
discussion is given of the dark matter in orbifold string compactifications
under constraints of modular invariance and radiative breaking of the
electroweak symmetry. Finally a new candidate for dark matter - an extra-weakly
interacting massive particle or an XWIMP- is discussed. Such dark matter can
arise in a wide class of models, including the Stueckelberg extensions of MSSM,
in U(1) extensions of MSSM with off diagonal kinetic energy, and possibly in a
wider class of models which may have a string/D-brane origin. Satisfaction of
the relic density of XWIMPs consistent with WMAP is also discussed.Comment: Invited talk at the International Conference "Idenfication of Dark
Matter-2006", September 11-16, 2006, Rhodes, Greece. 11 pages, 3 figure

### Evidence for Inflation in an Axion Landscape

We discuss inflation models within supersymmetry and supergravity frameworks
with a landscape of chiral superfields and one $U(1)$ shift symmetry which is
broken by non-perturbative symmetry breaking terms in the superpotential. We
label the pseudo scalar component of the chiral fields axions and their real
parts saxions. Thus in the models only one combination of axions will be a
pseudo-Nambu-Goldstone-boson which will act as the inflaton. The proposed
models constitute consistent inflation for the following reasons: The inflation
potential arises dynamically with stabilized saxions, the axion decay constant
can lie in the sub-Planckian region, and consistency with the Planck data is
achieved. The axion landscape consisting of $m$ axion pairs is assumed with the
axions in each pair having opposite charges. A fast roll--slow roll splitting
mechanism for the axion potential is proposed which is realized with a special
choice of the axion basis. In this basis the $2m$ coupled equations split into
$2m-1$ equations which enter in the fast roll and there is one unique linear
combination of the $2m$ fields which controls the slow roll and thus the power
spectrum of curvature and tensor perturbations. It is shown that a significant
part of the parameter space exists where inflation is successful, i.e., $N_{\rm
pivot} = {[50, 60]}$, the spectral index $n_s$ of curvature perturbations, and
the ratio $r$ of the power spectrum of tensor perturbations and curvature
perturbations, lie in the experimentally allowed regions given by the Planck
experiment. Further, it is shown that the model allows for a significant region
of the parameter space where the effective axion decay constant can lie in the
sub-Planckian domain.Comment: 31 pages, 10 figures. Accepted for publication in JHE

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