55 research outputs found
On Gravitino properties in a Conformal Supergravity Model
In the context of a conformal Supergravity (SUGRA) model in the Einstein
frame, in which the (next to) minimal supersymmetric standard model can
embedded naturally to produce chaotic inflation scenarios, we study properties
of gravitino in the cases where it is stable or unstable. In the latter case,
we demonstrate that for large dilaton scale factors there is an enhanced
magnitude of the gravitino width, when it decays to neutralino dark matter, as
compared with the standard SUGRA case. In this context, we discuss the
associated consequences as far as Big Bang Nucleosynthesis constraints and
avoidance of gravitino overproduction are concerned.Comment: 7 pages latex, two eps figures incorporate
High-Energy Constraints on the Direct Detection of MSSM Neutralinos
The requirement that the MSSM remain an acceptable effective field theory up
to energies beyond the weak scale constrains the sparticle spectrum, and hence
the permissible ranges of cold dark matter neutralino-proton cross sections.
Specifically, squarks are generally much heavier than sleptons if no tachyons
are to appear before the GUT scale ~10^16 GeV, or even before 10 TeV. We
display explicitly the allowed ranges of effective squark and slepton masses at
the weak scale, and the cross-section ranges allowed if the MSSM is to remain
valid without tachyons up to 10 TeV or the GUT scale. The allowed areas in the
cross section-mass plane for both spin-independent and spin-dependent
scattering are significantly smaller than would be allowed if the MSSM were
required to be valid only around the weak scale. In addition to a reduction in
the maximum cross section, the upper limit on the neutralino mass is greatly
reduced when tachyons are avoided, particularly for smaller values of the
squark masses.Comment: 22 pages, 22 figure
Metastable Charged Sparticles and the Cosmological Li7 Problem
We consider the effects of metastable charged sparticles on Big-Bang
Nucleosynthesis (BBN), including bound-state reaction rates and chemical
effects. We make a new analysis of the bound states of negatively-charged
massive particles with the light nuclei most prominent in BBN, and present a
new code to track their abundances, paying particular attention to that of Li7.
Assuming, as an example, that the gravitino is the lightest supersymmetric
particle (LSP), and that the lighter stau slepton, stau_1, is the metastable
next-to-lightest sparticle within the constrained minimal supersymmetric
extension of the Standard Model (CMSSM), we analyze the possible effects on the
standard BBN abundances of stau_1 bound states and decays for representative
values of the gravitino mass. Taking into account the constraint on the CMSSM
parameter space imposed by the discovery of the Higgs boson at the LHC, we
delineate regions in which the fit to the measured light-element abundances is
as good as in standard BBN. We also identify regions of the CMSSM parameter
space in which the bound state properties, chemistry and decays of metastable
charged sparticles can solve the cosmological Li7 problem.Comment: 49 pages, 29 eps figure
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