198 research outputs found

### Experimental Constraints on the Neutralino-Nucleon Cross Section

In the light of recent experimental results for the direct detection of dark
matter, we analyze in the framework of SUGRA the value of the
neutralino-nucleon cross section. We study how this value is modified when the
usual assumptions of universal soft terms and GUT scale are relaxed. In
particular we consider scenarios with non-universal scalar and gaugino masses
and scenarios with intermediate unification scale. We also study superstring
constructions with D-branes, where a combination of the above two scenarios
arises naturally. In the analysis we take into account the most recent
experimental constraints, such as the lower bound on the Higgs mass, the $b\to
s\gamma$ branching ratio, and the muon $g-2$.Comment: References added, bsgamma upper bound improved, results unchanged,
Talk given at Corfu Summer Institute on Elementary Particle Physics, August
31-September 20, 200

### Right-handed sneutrino as thermal dark matter

We study an extension of the MSSM with a singlet S with coupling SH1H2 in
order to solve the mu problem as in the NMSSM, and right-handed neutrinos N
with couplings SNN in order to generate dynamically electroweak-scale Majorana
masses. We show how in this model a purely right-handed sneutrino can be a
viable candidate for cold dark matter in the Universe. Through the direct
coupling to the singlet, the sneutrino can not only be thermal relic dark
matter but also have a large enough scattering cross section with nuclei to
detect it directly in near future, in contrast with most of other right-handed
sneutrino dark matter models.Comment: 5 pages, 2 figures. References added and minor changes. Final version
to appear in Phys. Rev.

### Calculable inverse-seesaw neutrino masses in supersymmetry

We provide a scenario where naturally small and calculable neutrino masses
arise from a supersymmetry breaking renormalization-group-induced vacuum
expectation value. We adopt a minimal supergravity scenario without ad hoc
supersymmetric mass parameters. The lightest supersymmetric particle can be an
isosinglet scalar neutrino state, potentially viable as WIMP dark matter
through its Higgs new boson coupling. The scenario leads to a plethora of new
phenomenological implications at accelerators including the Large Hadron
Collider.Comment: LaTeX, 5 pages, 4 figures. Comments and references added. Final
version to appear in PR

### Muon anomalous magnetic moment in supersymmetric scenarios with an intermediate scale and nonuniversality

We analyze the anomalous magnetic moment of the muon (a_{\mu}) in
supersymmetric scenarios. First we concentrate on scenarios with universal soft
terms. We find that a moderate increase of a_{\mu} can be obtained by lowering
the unification scale M_{GUT} to intermediate values 10^{10-12} GeV. However,
large values of \tan \beta are still favored. Then we study the case of
non-universal soft terms. For the usual value M_{GUT}~10^{16} GeV, we obtain
a_{\mu} in the favored experimental range even for moderate \tan \beta regions
\tan\beta ~ 5$. Finally, we give an explicit example of these scenarios. In
particular, we show that in a D-brane model, where the string scale is
naturally of order 10^{10-12} GeV and the soft terms are non universal, a_{\mu}
is enhanced with low \tan\beta.Comment: Final version to appear in Phys. Rev. D. Conventions clarified,
results in the figures improve

### Large dark matter cross sections from supergravity and superstrings

We study the direct detection of supersymmetric dark matter in the light of recent experimental results. In particular, we show that regions in the parameter space of several scenarios with a neutralino-nucleon cross section of the order of $10^{-6}$ pb, i.e., where current dark matter detectors are sensitive, can be obtained. These are supergravity scenarios with intermediate unification scale, and superstring scenarios with D-branes

### The XENON100 exclusion limit without considering Leff as a nuisance parameter

In 2011, the XENON100 experiment has set unprecedented constraints on dark
matter-nucleon interactions, excluding dark matter candidates with masses down
to 6 GeV if the corresponding cross section is larger than 10^{-39} cm^2. The
dependence of the exclusion limit in terms of the scintillation efficiency
(Leff) has been debated at length. To overcome possible criticisms XENON100
performed an analysis in which Leff was considered as a nuisance parameter and
its uncertainties were profiled out by using a Gaussian likelihood in which the
mean value corresponds to the best fit Leff value smoothly extrapolated to zero
below 3 keVnr. Although such a method seems fairly robust, it does not account
for more extreme types of extrapolation nor does it enable to anticipate on how
much the exclusion limit would vary if new data were to support a flat
behaviour for Leff below 3 keVnr, for example. Yet, such a question is crucial
for light dark matter models which are close to the published XENON100 limit.
To answer this issue, we use a maximum Likelihood ratio analysis, as done by
the XENON100 collaboration, but do not consider Leff as a nuisance parameter.
Instead, Leff is obtained directly from the fits to the data. This enables us
to define frequentist confidence intervals by marginalising over Leff.Comment: 10 pages;, 9 figures; references adde

### Modulus-dominated SUSY-breaking soft terms in F-theory and their test at LHC

We study the general patterns of SUSY-breaking soft terms arising under the
assumption of Kahler moduli dominated SUSY-breaking in string theory models.
Insisting that all MSSM gauginos get masses at leading order and that the top
Yukawa coupling is of order the gauge coupling constant identifies the class of
viable models. These are models in which the SM fields live either in the bulk
or at the intersection of local sets of Type IIB D7-branes or their F-theory
relatives. General arguments allow us to compute the dependence of the Kahler
metrics of MSSM fields on the local Kahler modulus of the brane configuration
in the large moduli approximation. We illustrate this study in the case of
toroidal/orbifold orientifolds but discuss how the findings generalize to the
F-theory case which is more naturally compatible with coupling unification.
Only three types of 7-brane configurations are possible, leading each of them
to very constrained patterns of soft terms for the MSSM. We study their
consistency with radiative electroweak symmetry breaking and other
phenomenological constraints. We find that essentially only the configuration
corresponding to intersecting 7-branes is compatible with all present
experimental constraints and the desired abundance of neutralino dark matter.
The obtained MSSM spectrum is very characteristic and could be tested at LHC.
We also study the LHC reach for the discovery of this type of SUSY particle
spectra.Comment: 60 pages, 7 figures, 2 tables. References adde

### Probing neutralino dark matter in the MSSM & the NMSSM with directional detection

We investigate the capability of directional detectors to probe neutralino
dark matter in the Minimal Supersymmetric Standard Model and the
Next-to-Minimal Supersymmetric Standard Model with parameters defined at the
weak scale. We show that directional detectors such as the future MIMAC
detector will probe spin dependent dark matter scattering on nucleons that are
beyond the reach of current spin independent detectors. The complementarity
between indirect searches, in particular using gamma rays from dwarf spheroidal
galaxies, spin dependent and spin independent direct search techniques is
emphasized. We comment on the impact of the negative results on squark searches
at the LHC. Finally, we investigate how the fundamental parameters of the
models can be constrained in the event of a dark matter signal.Comment: 21 pages, 16 figure

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