42 research outputs found
Prospects for the direct detection of neutralino dark matter in orbifold scenarios
51 pages, 25 figures.We analyse the phenomenology of orbifold scenarios from the heterotic superstring, and the resulting theoretical predictions for the direct detection of neutralino dark matter. In particular, we study the parameter space of these constructions, computing the low-energy spectrum and taking into account the most recent experimental and astrophysical constraints, as well as imposing the absence of dangerous charge and colour breaking minima. In the remaining allowed regions the spin-independent part of the neutralino-proton cross section is calculated and compared with the sensitivity of dark matter detectors. In addition to the usual non universalities of the soft terms in orbifold scenarios due to the modular weight dependence, we also consider D-term contributions to scalar masses. These are generated by the presence of an anomalous U(1), providing more flexibility in the resulting soft terms, and are crucial in order to avoid charge and colour breaking minima. Thanks to the D-term contribution, large neutralino detection cross sections can be found, within the reach of projected dark matter detectors.D.G. Cerdeño is supported by the program "Juan de la Cierva" of the Ministerio de Educación y Ciencia of Spain. T. Kobayashi is supported in part by the Grand-in-Aid for Scientific Research #17540251 and the Grant-in-Aid for the 21st Century COE "The Center for Diversity and Universality in Physics" from the Ministry of Education, Culture, Sports, Science and Technology of Japan. The work of C. Muñoz was supported in part by the Spanish DGI of the MEC under Proyecto Nacional FPA2006-
05423, by the European Union under the RTN program MRTN-CT-2004-503369, and under the ENTApP Network of the ILIAS project RII3-CT-2004-506222. Likewise, the work of D. G. Cerdeño and C. Muñoz, was also supported in part by the Spanish DGI of the MEC under Proyecto Nacional FPA2006-01105, by the Comunidad de Madrid under Proyecto HEPHACOS, Ayudas de I+D S-0505/ESP-0346, and by the EU research and training network MRTN-CT-2006-035863
Constraints from the duration of supernova neutrino burst on resonant light gauge boson production by neutrinos
In this article, we study the resonant production of low-mass vector
mediators from neutrino-antineutrino coalescence in the core of proto-neutron
stars. Taking into account the radial dependence of the density, energy, and
temperature inside the proto-neutron star, we compute the neutrino-antineutrino
interaction rate in the star interior in the well-motivated
model. First, we determine the values of the coupling
above which neutrino-antineutrino interactions dominate over the Standard Model
neutrino-nucleon scattering. We argue that, although in this regime a
redistribution of the neutrino energies might take place, making low-energy
neutrinos more trapped, this only affects a small part of the neutrino
population and it cannot be constrained with the SN 1987A data. Thus, contrary
to previous claims, the region of the parameter space where the
model explains the discrepancy in the muon anomalous
magnetic moment is not ruled out. We then focus on small gauge couplings, where
the decay length of the new gauge boson is larger than the neutrino-nucleon
mean free path, but still smaller than the size of proto-neutron star. We show
for the first time that in this regime, the resonant production of a long-lived
and its subsequent decay into neutrinos can significantly reduce the
duration of the neutrino burst, probing values of the coupling below for mediator masses between 10 and 100~MeV. This rules out new
areas of the parameter space of the model.Comment: 21 pages, 5 figures. Major changes: Confirming previous results but
ruling out new ranges of parameter
How to calculate dark matter direct detection exclusion limits that are consistent with gamma rays from annihilation in the Milky Way halo
When comparing constraints on the weakly interacting massive particle (WIMP) properties from direct and indirect detection experiments it is crucial that the assumptions made about the dark matter (DM) distribution are realistic and consistent. For instance, if the Fermi-LAT Galactic center GeV gamma-ray excess was due to WIMP annihilation, its morphology would be incompatible with the standard halo model that is usually used to interpret data from direct detection experiments. In this article, we calculate exclusion limits from direct detection experiments using self-consistent velocity distributions, derived from mass models of the Milky Way where the DM halo has a generalized Navarro-Frenk-White profile. We use two different methods to make the mass model compatible with a DM interpretation of the Galactic center gamma-ray excess. First, we fix the inner slope of the DM density profile to the value that best fits the morphology of the excess. Second, we allow the inner slope to vary and include the morphology of the excess in the data sets used to constrain the gravitational potential of the Milky Way. The resulting direct detection limits differ significantly from those derived using the standard halo model, in particular for light WIMPs, due to the differences in both the local DM density and velocity distribution
SuperCDMS: Recent results on low-mass WIMPs
We present the rst search for weakly interacting massive particles (WIMPs) using the back- ground rejection capabilities of SuperCDMS 1. A blind analysis of data from an exposure of 577 kg-days leads to an upper limit on the spin-independent WIMP-nucleon cross section of 1:2 10????42 cm2 at 8 GeV. This result probes new parameter space for WIMP-nucleon scat- tering cross section for light WIMPs with masses < 6 GeV/c2 and is in tension with WIMP interpretations of recent experiments
Direct detection of neutralino dark matter in supergravity
The direct detection of neutralino dark matter is analysed in general
supergravity scenarios, where non-universal soft scalar and gaugino masses can
be present. In particular, the theoretical predictions for the
neutralino-nucleon cross section are studied and compared with the sensitivity
of dark matter detectors. We take into account the most recent astrophysical
and experimental constraints on the parameter space, including the current
limit on B(Bs-> mu+ mu-). The latter puts severe limitations on the dark matter
scattering cross section, ruling out most of the regions that would be within
the reach of present experiments. We show how this constraint can be softened
with the help of appropriate choices of non-universal parameters which increase
the Higgsino composition of the lightest neutralino and minimise the chargino
contribution to the b->s transition.Comment: 27 pages, 22 figure
Prospects for the direct detection of neutralino dark matter in orbifold scenarios
We analyse the phenomenology of orbifold scenarios from the heterotic
superstring, and the resulting theoretical predictions for the direct detection
of neutralino dark matter. In particular, we study the parameter space of these
constructions, computing the low-energy spectrum and taking into account the
most recent experimental and astrophysical constraints, as well as imposing the
absence of dangerous charge and colour breaking minima. In the remaining
allowed regions the spin-independent part of the neutralino-proton cross
section is calculated and compared with the sensitivity of dark matter
detectors. In addition to the usual non universalities of the soft terms in
orbifold scenarios due to the modular weight dependence, we also consider
D-term contributions to scalar masses. These are generated by the presence of
an anomalous U(1), providing more flexibility in the resulting soft terms, and
are crucial in order to avoid charge and colour breaking minima. Thanks to the
D-term contribution, large neutralino detection cross sections can be found,
within the reach of projected dark matter detectors.Comment: 51 pages, 25 figure
Stau detection at neutrino telescopes in scenarios with supersymmetric dark matter
We have studied the detection of long-lived staus at the IceCube neutrino
telescope, after their production inside the Earth through the inelastic
scattering of high energy neutrinos. The theoretical predictions for the stau
flux are calculated in two scenarios in which the presence of long-lived staus
is naturally associated to viable supersymmetric dark matter. Namely, we
consider the cases with superWIMP (gravitino or axino) and neutralino dark
matter (along the coannihilation region). In both scenarios the maximum value
of the stau flux turns out to be about 1 event/yr in regions with a light stau.
This is consistent with light gravitinos, with masses constrained by an upper
limit which ranges from 0.2 to 15 GeV, depending on the stau mass. Likewise, it
is compatible with axinos with a mass of about 1 GeV and a very low reheating
temperature of order 100 GeV. In the case of the neutralino dark matter this
favours regions with a low value of tan(beta), for which the neutralino-stau
coannihilation region occurs for smaller values of the stau mass. Finally, we
study the case of a general supergravity theory and show how for specific
choices of non-universal soft parameters the predicted stau flux can increase
moderately.Comment: 26 pages, 7 figures. References added and minor changes. Final
version to appear in JCA
Further characterization of autoantibodies to GABAergic neurons in the central nervous system produced by a subset of children with autism
<p>Abstract</p> <p>Background</p> <p>Autism is a neurodevelopmental disorder characterized by impairments in social interaction and deficits in verbal and nonverbal communication, together with the presence of repetitive behaviors or a limited repertoire of activities and interests. The causes of autism are currently unclear. In a previous study, we determined that 21% of children with autism have plasma autoantibodies that are immunoreactive with a population of neurons in the cerebellum that appear to be Golgi cells, which are GABAergic interneurons.</p> <p>Methods</p> <p>We have extended this analysis by examining plasma immunoreactivity in the remainder of the brain. To determine cell specificity, double-labeling studies that included one of the calcium-binding proteins that are commonly colocalized in GABAergic neurons (calbindin, parvalbumin or calretinin) were also carried out to determine which GABAergic neurons are immunoreactive. Coronal sections through the rostrocaudal extent of the macaque monkey brain were reacted with plasma from each of seven individuals with autism who had previously demonstrated positive Golgi cell staining, as well as six negative controls. In addition, brain sections from adult male mice were similarly examined.</p> <p>Results</p> <p>In each case, specific staining was observed for neurons that had the morphological appearance of interneurons. By double-labeling sections with plasma and with antibodies directed against γ-aminobutyric acid (GABA), we determined that all autoantibody-positive neurons were GABAergic. However, not all GABAergic neurons were autoantibody-positive. Calbindin was colabeled in several of the autoantibody-labeled cells, while parvalbumin colabeling was less frequently observed. Autoantibody-positive cells rarely expressed calretinin. Sections from the mouse brain processed similarly to the primate sections also demonstrated immunoreactivity to interneurons distributed throughout the neocortex and many subcortical regions. Some cell populations stained in the primate (such as the Golgi neurons in the cerebellum) were not as robustly immunoreactive in the mouse brain.</p> <p>Conclusions</p> <p>These results suggest that the earlier report of autoantibody immunoreactivity to specific cells in the cerebellum extend to other regions of the brain. Further, these findings confirm the autoantibody-targeted cells to be a subpopulation of GABAergic interneurons. The potential impact of these autoantibodies on GABAergic disruption with respect to the etiology of autism is discussed herein.</p
Neutralino-Nucleon Cross Section and Charge and Colour Breaking Constraints
We compute the neutralino-nucleon cross section in several supersymmetric
scenarios, taking into account all kind of constraints. In particular, the
constraints that the absence of dangerous charge and colour breaking minima
imposes on the parameter space are studied in detail. In addition, the most
recent experimental constraints, such as the lower bound on the Higgs mass, the
branching ratio, and the muon are considered. The
astrophysical bounds on the dark matter density are also imposed on the
theoretical computation of the relic neutralino density, assuming thermal
production. This computation is relevant for the theoretical analysis of the
direct detection of dark matter in current experiments. We consider first the
supergravity scenario with universal soft terms and GUT scale. In this scenario
the charge and colour breaking constraints turn out to be quite important, and
\tan\beta\lsim 20 is forbidden. Larger values of can also be
forbidden, depending on the value of the trilinear parameter . Finally, we
study supergravity scenarios with an intermediate scale, and also with
non-universal scalar and gaugino masses where the cross section can be very
large.Comment: Final version to appear in JHE