3 research outputs found
Yukawa Unification, b --> s gamma and Bino-Stau Coannihilation
The minimal supersymmetric standard model with universal boundary conditions
and "asymptotic" Yukawa unification is considered. The full one-loop effective
potential for radiative electroweak symmetry breaking as well as the one-loop
corrections to the charged Higgs boson, b-quark and tau lepton masses are
included. The CP-even Higgs boson masses are corrected to two-loops. The relic
abundance of the lightest supersymmetric particle (bino) is calculated by
including its coannihilations with the next-to-lightest supersymmetric particle
(lightest stau) consistently with Yukawa unification. The branching ratio of b
--> s gamma is evaluated by incorporating all the applicable next-to-leading
order QCD corrections. The bino-stau coannihilations reduce the bino relic
abundance below the upper bound from cold dark matter considerations in a
sizable fraction of the parameter space allowed by b --> s gamma for mu>0.
Thus, the mu>0 case, which also predicts an acceptable b-quark mass, is
perfectly compatible with data.Comment: 16 pages including 3 figures, Revtex, major revisions are mad
Cold Dark Matter and b --> s gamma in the Horava-Witten Theory
The minimal supersymmetric standard model with complete, partial or no Yukawa
unification and radiative electroweak breaking with boundary conditions from
the Horava-Witten theory is considered. The parameters are restricted by
constraining the lightest sparticle relic abundance by cold dark matter
considerations and requiring the b-quark mass after supersymmetric corrections
and the branching ratio of b --> s gamma to be compatible with data. Complete
Yukawa unification can be excluded. Also, t-b Yukawa unification is strongly
disfavored since it requires almost degenerate lightest and next-to-lightest
sparticle masses. However, the b-tau or no Yukawa unification cases avoid this
degeneracy. The latter with mu<0 is the most natural case. The lightest
sparticle mass, in this case, can be as low as about 77 GeV.Comment: 16 pages including 4 figures, Revtex, version to appear in Phys.
Lett.
Cold Dark Matter detection in SUSY models at large tan(beta)
We study the direct detection rate for SUSY cold dark matter (CDM) predicted
by the minimal supersymmetric standard model with universal boundary conditions
and large values for tan(beta). The relic abundance of the lightest
supersymmetric particle (LSP), assumed to be approximately a bino, is obtained
by including its coannihilations with the next-to-lightest supersymmetric
particle (NLSP), which is the lightest s-tau. The cosmological constraint on
this quantity severely limits the allowed SUSY parameter space, especially in
the case the CP-even Higgs has mass of around 114 GeV. We find that for large
tan(beta) it is possible to find a subsection of the allowed parameter space,
which yields detectable rates in the currently planned experiments.Comment: Changes in text and figure