535 research outputs found
Partial wave treatment of Supersymmetric Dark Matter in the presence of CP - violation
We present an improved partial wave analysis of the dominant LSP annihilation
channel to a fermion-antifermion pair which avoids the non-relativistic
expansion being therefore applicable near thresholds and poles. The method we
develop allows of contributions of any partial wave in the total angular
momentum J in contrast to partial wave analyses in terms of the orbital angular
momentum L of the initial state, which is usually truncated to p-waves, and
yields very accurate results. The method is formulated in such a way as to
allow easy handling of CP-violating phases residing in supersymmetric
parameters. We apply this refined partial wave technique in order to calculate
the neutralino relic density in the constrained MSSM (CMSSM) in the presence of
CP-violating terms occurring in the Higgs - mixing parameter \mu and trilinear
A coupling for large tanb. The inclusion of CP-violating phases in mu and A
does not upset significantly the picture and the annihilation of the LSP's to a
b b_bar, through Higgs exchange, is still the dominant mechanism in obtaining
cosmologically acceptable neutralino relic densities in regions far from the
stau-coannihilation and the `focus point'. Significant changes can occur if we
allow for phases in the gaugino masses and in particular the gluino mass.Comment: 23 pages LaTeX, 10 eps figures, version to appear in PR
Inflating Intersecting Branes and Remarks on the Hierarchy Problem
We generalize solutions of Einstein's equations for intersecting branes in
higher dimensional spacetimes to the nonstatic case, modeling an expanding
universe. The relation between the Hubble rate, the brane tensions, and the
bulk cosmological constant is similar to the case of a single 3-brane in a
5-dimensional spacetime. However, because the bulk inflates as well as the
branes, this class of solutions suffers from Newton's constant tending toward
zero on the TeV brane, where the Randall-Sundrum mechanism should solve the
weak scale hierarchy problem. The strength of gravity remains constant on the
Planck brane, however.Comment: 10 pages, LaTeX. v2:Misprint in eq. (23) corrected; citations fixed
and clarified relationship of our work to hep-th/9909053 and hep-th/9909076
v3: final version to appear in PLB. Corrected discussion of the time
dependance of the 4-D Planck mass on the TeV brane. Some references added to
earlier works on warped Kaluza-Klein compactification
Exact Cross Sections for the Neutralino WIMP Pair-Annihilation
We derive a full set of exact, analytic expressions for the annihilation of
the lightest neutralino pairs into all two-body tree-level final states in the
framework of minimal supersymmetry. We make no simplifying assumptions about
the neutralino nor about sfermion masses and mixings other than the absence of
explicit CP--violating terms. The expressions should be particularly useful in
computing the neutralino WIMP relic abundance without the usual approximation
of partial wave expansion.Comment: LaTeX, 46 pages, no figures. Several minor typographical errors
correcte
Upper and Lower Limits on Neutralino WIMP Mass and Spin--Independent Scattering Cross Section, and Impact of New (g-2)_{mu} Measurement
We derive the allowed ranges of the spin--independent interaction cross
section \sigsip for the elastic scattering of neutralinos on proton for wide
ranges of parameters of the general Minimal Supersymmetric Standard Model. We
investigate the effects of the lower limits on Higgs and superpartner masses
from colliders, as well as the impact of constraints from \bsgamma and the
new measurement of \gmtwo on the upper and lower limits on \sigsip. We
further explore the impact of the neutralino relic density, including
coannihilation, and of theoretical assumptions about the largest allowed values
of the supersymmetric parameters. For , requiring the latter to lie
below 1\tev leads to \sigsip\gsim 10^{-11}\pb at \mchi\sim100\gev and
\sigsip\gsim 10^{-8}\pb at \mchi\sim1\tev. When the supersymmetric
parameters are allowed above 1\tev, for 440\gev \lsim \mchi\lsim 1020 \gev
we derive a {\em parameter--independent lower limit} of \sigsip \gsim 2\times
10^{-12}\pb. (No similar lower limits can be set for nor for
1020\gev\lsim\mchi\lsim2.6\tev.) Requiring \abundchi<0.3 implies a {\em
parameter--independent upper limit} \mchi\lsim2.6\tev. The new \epem--based
measurement of restricts \mchi\lsim 350\gev at CL
and \mchi\lsim515\gev at CL, and implies . The largest
allowed values of \sigsip have already become accessible to recent
experimental searches.Comment: LaTeX, 17 pages, 9 eps figures. Version to appear in JHE
Spectrum from the warped compactifications with the de Sitter universe
We discuss the spectrum of the tensor metric perturbations and the stability
of warped compactifications with the de Sitter spacetime in the
higher-dimensional gravity. The spacetime structure is given in terms of the
warped product of the non-compact direction, the spherical internal dimensions
and the four-dimensional de Sitter spacetime. To realize a finite bulk volume,
we construct the brane world model, using the cut-copy-paste method. Then, we
compactify the spherical directions on the brane. In any case, we show the
existence of the massless zero mode and the mass gap of it with massive
Kaluza-Klein modes. Although the brane involves the spherical dimensions, no
light massive mode is excited. We also investigate the scalar perturbations,
and show that the model is unstable due to the existence of a tachyonic bound
state, which seems to have the universal negative mass square, irrespective of
the number of spacetime dimensions.Comment: Journal version (JHEP
Inflation and Gauge Hierarchy in Randall-Sundrum Compactification
We obtain the general inflationary solutions for the slab of five-dimensional
AdS spacetime where the fifth dimension is an orbifold and two
three-branes reside at its boundaries, of which the Randall-Sundrum model
corresponds to the static limit. The investigation of the general solutions and
their static limit reveals that the RS model recasts both the cosmological
constant problem and the gauge hierarchy problem into the balancing problem of
the bulk and the brane cosmological constants.Comment: 9 pages, revtex, minor changes and more references adde
Effective Gauss-Bonnet Interaction in Randall-Sundrum Compactification
The effective gravitational interaction below the Planck scale in the
Randall-Sundrum world is shown to be the Gauss-Bonnet term. In this theory we
find that there exists another static solution with a positive bulk
cosmological constant. Also, there exist solutions for positive visible sector
cosmological constant, which are needed for a later Friedman-Robertson-Walker
universe.Comment: 10 pages, including 1 eps figur
On Yukawa quasi-unification with mu<0
Although recent data on the muon anomalous magnetic moment strongly disfavor
the constrained minimal supersymmetric standard model with mu<0, they cannot
exclude it because of theoretical ambiguities. We consider this model
supplemented by a Yukawa quasi-unification condition which allows an acceptable
b-quark mass. We find that the cosmological upper bound on the lightest
sparticle relic abundance is incompatible with the data on the branching ratio
of b-->s gamma, which is evaluated by including all the next-to-leading order
corrections. Thus, this scheme is not viable.Comment: 4 pages including 3 figures, Revte
A Statistical Analysis of Supersymmetric Dark Matter in the MSSM after WMAP
We study supersymmetric dark matter in the general flavor diagonal MSSM by
means of an extensive random scan of its parameter space. We find that, in
contrast with the standard mSUGRA lore, the large majority of viable models
features either a higgsino or a wino-like lightest neutralino, and yields a
relic abundance well below the WMAP bound. Among the models with neutralino
relic density within the WMAP range, higgsino-like neutralinos are still
dominant, though a sizeable fraction of binos is also present. In this latter
case, relic density suppression mechanisms are shown to be essential in order
to obtain the correct neutralino abundance. We then carry out a statistical
analysis and a general discussion of neutralino dark matter direct detection
and of indirect neutralino detection at neutrino telescopes and at antimatter
search experiments. We point out that current data exclude only a marginal
portion of the viable parameter space, and that models whose thermal relic
abundance lies in the WMAP range will be significantly probed only at future
direct detection experiments. Finally, we emphasize the importance of relic
density enhancement mechanisms for indirect detection perspectives, in
particular at future antimatter search experiments.Comment: 39 pages, 25 figure
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