4,293 research outputs found
A Minimal SU(5) SuperGUT in Pure Gravity Mediation
The lack of evidence for low-scale supersymmetry suggests that the scale of
supersymmetry breaking may be higher than originally anticipated. However,
there remain many motivations for supersymmetry including gauge coupling
unification and a stable dark matter candidate. Models like pure gravity
mediation (PGM) evade LHC searches while still providing a good dark matter
candidate and gauge coupling unification. Here, we study the effects of PGM if
the input boundary conditions for soft supersymmetry breaking masses are pushed
beyond the unification scale and higher dimensional operators are included. The
added running beyond the unification scale opens up the parameter space by
relaxing the constraints on . If higher dimensional operators
involving the SU(5) adjoint Higgs are included, the mass of the heavy gauge
bosons of SU(5) can be suppressed leading to proton decay, ,
that is within reach of future experiments. Higher dimensional operators
involving the supersymmetry breaking field can generate additional
contributions to the A- and B-terms of order . The threshold effects
involving these A- and B-terms significantly impact the masses of the gauginos
and can lead to a bino LSP. In some regions of parameter space the bino can be
degenerate with the wino or gluino and give an acceptable dark matter relic
density.Comment: 37 pages, 27 figure
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Scenarios for Gluino Coannihilation
We study supersymmetric scenarios in which the gluino is the next-to-lightest
supersymmetric particle (NLSP), with a mass sufficiently close to that of the
lightest supersymmetric particle (LSP) that gluino coannihilation becomes
important. One of these scenarios is the MSSM with soft supersymmetry-breaking
squark and slepton masses that are universal at an input GUT renormalization
scale, but with non-universal gaugino masses. The other scenario is an
extension of the MSSM to include vector-like supermultiplets. In both
scenarios, we identify the regions of parameter space where gluino
coannihilation is important, and discuss their relations to other regions of
parameter space where other mechanisms bring the dark matter density into the
range allowed by cosmology. In the case of the non-universal MSSM scenario, we
find that the allowed range of parameter space is constrained by the
requirement of electroweak symmetry breaking, the avoidance of a charged LSP
and the measured mass of the Higgs boson, in particular, as well as the
appearance of other dark matter (co)annihilation processes. Nevertheless, LSP
masses ~TeV with the correct dark matter density are quite
possible. In the case of pure gravity mediation with additional vector-like
supermultiplets, changes to the anomaly-mediated gluino mass and the threshold
effects associated with these states can make the gluino almost degenerate with
the LSP, and we find a similar upper bound.Comment: 25 pages, 22 figure
On the Feasibility of a Stop NLSP in Gravitino Dark Matter Scenarios
We analyze the possibility that the lighter stop {\tilde t_1} could be the
next-to-lightest supersymmetric particle (NLSP) in models where the gravitino
is the lightest supersymmetric particle (LSP). We do not find any possibility
for a stop NLSP in the constrained MSSM with universal input soft
supersymmetry-breaking masses at the GUT scale (CMSSM), but do find small
allowed regions in models with non-universal Higgs masses (NUHM). We discuss
the cosmological evolution of stop hadrons. Most {\tilde t_1}qq `sbaryons' and
the corresponding `antisbaryons' annihilate with conventional antibaryons and
baryons into {\tilde t_1}{\bar q} `mesinos' and the corresponding
`antimesinos', respectively, shortly after the quark-hadron transition in the
early Universe, and most mesinos and antimesinos subsequently annihilate. As a
result, insufficient metastable charged stop hadrons survive to alter Big Bang
nucleosynthesis.Comment: 31 pages, 14 figure
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