19 research outputs found
Naturalness of Neutralino Dark Matter
We investigate the level of fine-tuning of neutralino Dark Matter below 200
GeV in the low-energy phenomenological minimal supersymmetric Standard Model
taking into account the newest results from XENON100 and the Large Hadron
Collider as well as all other experimental bounds from collider physics and the
cosmological abundance. We find that current and future direct Dark Matter
searches significantly rule out a large area of the untuned parameter space,
but solutions survive which do not increase the level of fine-tuning. As
expected, the level of tuning tends to increase for lower cross-sections, but
regions of resonant neutralino annihilation still allow for a band at light
masses, where the fine-tuning stays small even below the current experimental
limits for direct detection cross-sections. For positive values of the
supersymmetric Higgs mass parameter \mu large portions of the allowed parameter
space are excluded, but there still exist untuned solutions at higher
neutralino masses which will essentially be ruled out if XENON1t does not
observe a signal.For negative \mu untuned solutions are not much constrained by
current limits of direct searches and, if the neutralino mass was found outside
the resonance regions, a negative \mu-term would be favored from a fine-tuning
perspective. Light stau annihilation plays an important role to fulfill the
relic density condition in certain neutralino mass regions. Finally we discuss,
in addition to the amount of tuning for certain regions in the neutralino
mass-direct detection cross-section plane, the parameter mapping distribution
if the allowed model parameter space is chosen to be scanned homogeneously
(randomized).Comment: v2: 29 pages, 16 figures. Published versio
LHC Tests of Light Neutralino Dark Matter without Light Sfermions
We address the question how light the lightest MSSM neutralino can be as dark
matter candidate in a scenario where all supersymmetric scalar particles are
heavy. The hypothesis that the neutralino accounts for the observed dark matter
density sets strong requirements on the supersymmetric spectrum, thus providing
an handle for collider tests. In particular for a lightest neutralino below 100
GeV the relic density constraint translates into an upper bound on the Higgsino
mass parameter in case all supersymmetric scalar particles are heavy. One
can define a simplified model that highlights only the necessary features of
the spectrum and their observable consequences at the LHC. Reinterpreting
recent searches at the LHC we derive limits on the mass of the lightest
neutralino that, in many cases, prove to be more constraining than dark matter
experiments themselves.Comment: 22 pages, 8 figure
Asymmetric Mediator in Scotogenic Model
The scotogenic model is the Standard Model (SM) with Z_2 symmetry and the
addition of Z_2 odd right-handed Majorana neutrinos and SU(2)_L doublet scalar
fields. We have extended the original scotogenic model by an additional Z_2 odd
singlet scalar field that plays a role in dark matter. In our model, the
asymmetries of the lepton and Z_2 odd doublet scalar are simultaneously
produced through CP-violating right-handed neutrino decays. While the former is
converted into baryon asymmetry through the sphaleron process, the latter is
relaid to the DM density through the decay of SU(2)_L doublet scalar that is
named "asymmetric mediator". In this way, we provide an extended scotogenic
model that predicts the energy densities of baryon and dark matter being in the
same order of magnitude, and also explains the low-energy neutrino masses and
mixing angles.Comment: 17 pages, 1 table, 5 figure
Model Building by Coset Space Dimensional Reduction Scheme Using Twelve-Dimensional Coset Spaces
We investigate the twelve-dimensional gauge-Higgs unification models with an
eight-dimensional coset space. For each model, we apply the coset space
dimensional reduction procedure and examine the particle contents of the
resulting four-dimensional theory. Then, some twelve-dimensional SO(18) gauge
theories lead to models of the SO(10)\times U(1) grand unified theory in four
dimensions, where fermions of the Standard Model appear in multiple generations
along with scalars that may break the electroweak symmetry. The representations
of the obtained scalars and fermions are summarized.Comment: 17 pages, 4 table
Light neutralino in the MSSM: An update with the latest LHC results
We discuss the scenario of light neutralino dark matter in the minimal
supersymmetric standard model, which is motivated by the results of some of the
direct detection experiments --- DAMA, CoGENT, and CRESST. We update our
previous analysis with the latest results of the LHC. We show that new LHC
constraints disfavour the parameter region that can reproduce the results of
DAMA and CoGENT.Comment: 4 pages, 4 figures, to appear in the conference proceedings of TAUP
2011, Munich Germany, 5-9 September 201