7 research outputs found
Fine-tuning implications for complementary dark matter and LHC SUSY searches
The requirement that SUSY should solve the hierarchy problem without undue
fine-tuning imposes severe constraints on the new supersymmetric states. With
the MSSM spectrum and soft SUSY breaking originating from universal scalar and
gaugino masses at the Grand Unification scale, we show that the low-fine-tuned
regions fall into two classes that will require complementary collider and dark
matter searches to explore in the near future. The first class has relatively
light gluinos or squarks which should be found by the LHC in its first run. We
identify the multijet plus E_T^miss signal as the optimal channel and determine
the discovery potential in the first run. The second class has heavier gluinos
and squarks but the LSP has a significant Higgsino component and should be seen
by the next generation of direct dark matter detection experiments. The
combined information from the 7 TeV LHC run and the next generation of direct
detection experiments can test almost all of the CMSSM parameter space
consistent with dark matter and EW constraints, corresponding to a fine-tuning
not worse than 1:100. To cover the complete low-fine-tuned region by SUSY
searches at the LHC will require running at the full 14 TeV CM energy; in
addition it may be tested indirectly by Higgs searches covering the mass range
below 120 GeV.Comment: References added. Version accepted for publication in JHE
Dark matter allowed scenarios for Yukawa-unified SO(10) SUSY GUTs
Simple supersymmetric grand unified models based on the gauge group SO(10)
require --in addition to gauge and matter unification-- the unification of
t-b-\tau Yukawa couplings. Yukawa unification, however, only occurs for very
special values of the soft SUSY breaking parameters. We perform a search using
a Markov Chain Monte Carlo (MCMC) technique to investigate model parameters and
sparticle mass spectra which occur in Yukawa-unified SUSY models, where we also
require the relic density of neutralino dark matter to saturate the
WMAP-measured abundance. We find the spectrum is characterizd by three mass
scales: first/second generation scalars in the multi-TeV range, third
generation scalars in the TeV range, and gauginos in the \sim 100 GeV range.
Most solutions give far too high a relic abundance of neutralino dark matter.
The dark matter discrepancy can be rectified by 1. allowing for neutralino
decay to axino plus photon, 2. imposing gaugino mass non-universality or 3.
imposing generational non-universality. In addition, the MCMC approach finds 4.
a compromise solution where scalar masses are not too heavy, and where
neutralino annihilation occurs via the light Higgs h resonance. By imposing
weak scale Higgs soft term boundary conditions, we are also able to generate 5.
low \mu, m_A solutions with neutralino annihilation via a light A resonance,
though these solutions seem to be excluded by CDF/D0 measurements of the B_s\to
\mu^+\mu^- branching fraction. Based on the dual requirements of Yukawa
coupling unification and dark matter relic density, we predict new physics
signals at the LHC from pair production of 350--450 GeV gluinos. The events are
characterized by very high b-jet multiplicity and a dilepton mass edge around
mz2-mz1 \sim 50-75 GeV.Comment: 35 pages with 21 eps figure
A note on the primordial abundance of stau NLSPs
In scenarios with a gravitino LSP, there exist strong BBN constraints on the
abundance of a possible stau NLSP. We find that in settings with substantial
left-right mixing of the stau mass eigenstates these constraints can be evaded
even for very long-lived staus.Comment: 17 pages, 5 figures, discussion on vacuum stability adde
Dark Matter Candidates: A Ten-Point Test
An extraordinarily rich zoo of non-baryonic Dark Matter candidates has been
proposed over the last three decades. Here we present a 10-point test that a
new particle has to pass, in order to be considered a viable DM candidate: I.)
Does it match the appropriate relic density? II.) Is it {\it cold}? III.) Is it
neutral? IV.) Is it consistent with BBN? V.) Does it leave stellar evolution
unchanged? VI.) Is it compatible with constraints on self-interactions? VII.)
Is it consistent with {\it direct} DM searches? VIII.) Is it compatible with
gamma-ray constraints? IX.) Is it compatible with other astrophysical bounds?
X.) Can it be probed experimentally?Comment: 29 pages, 12 figure
Cosmological consequences of Yukawa-unified SUSY with mixed axion/axino cold and warm dark matter
Supersymmetric models with t-b-\tau Yukawa unification at M_{GUT}
qualitatively predict a sparticle mass spectrum including first and second
generation scalars at the 3--15 TeV scale, third generation scalars at the
(few) TeV scale and gluinos in the sub-TeV range. The neutralino relic density
in these models typically turns out to lie far above the measured dark matter
abundance, prompting the suggestion that instead dark matter is composed of an
axion/axino mixture. We explore the axion and thermal and non-thermal axino
dark matter abundance in Yukawa-unified SUSY models. We find in this scenario
that {\it i}). rather large values of Peccei-Quinn symmetry breaking scale
f_a\sim 10^{12} GeV are favored and {\it ii}). rather large values of GUT scale
scalar masses \sim 10-15 TeV allow for the re-heat temperature T_R of the
universe to be T_R\agt 10^6 GeV. This allows in turn a solution to the
gravitino/Big Bang Nucleosynthesis problem while also allowing for baryogenesis
via non-thermal leptogenesis. The large scalar masses for Yukawa-unified models
are also favored by data on b\to s\gamma and B_s\to \mu^+\mu^- decay. Testable
consequences from this scenario include a variety of robust LHC signatures, a
possible axion detection at axion search experiments, but null results from
direct and indirect WIMP search experiments.Comment: 27 pages including 16 EPS figure
The Number Density of a Charged Relic.
We investigate scenarios in which a charged, long-lived scalar particle
decouples from the primordial plasma in the Early Universe. We compute the
number density at time of freeze-out considering both the cases of abelian and
non-abelian interactions and including the effect of Sommerfeld enhancement at
low initial velocity. We also discuss as extreme case the maximal cross section
that fulfils the unitarity bound. We then compare these number densities to the
exotic nuclei searches for stable relics and to the BBN bounds on unstable
relics and draw conclusions for the cases of a stau or stop NLSP in
supersymmetric models with a gravitino or axino LSP.Comment: 45 page