77 research outputs found
Cosmological bounds on pseudo Nambu-Goldstone bosons
We review the cosmological implications of a relic population of pseudo
Nambu-Goldstone bosons (pNGB) with an anomalous coupling to two photons, often
called axion-like particles (ALPs). We establish constraints on the pNGB mass
and two-photon coupling by considering big bang nucleosynthesis, the physics of
the cosmic microwave background, and the diffuse photon background. The bounds
from WMAP7 and other large-scale-structure data on the effective number of
neutrino species can be stronger than the traditional bounds from the
primordial helium abundance. These bounds, together with those from primordial
deuterium abundance, constitute the most stringent probes of early decays.Comment: 29 pages, 13 pictures. Enlarged discussions on BBN and recombination
constraints. One figure and several references added. Version accepted in
JCA
Antiproton constraints on dark matter annihilations from internal electroweak bremsstrahlung
If the dark matter particle is a Majorana fermion, annihilations into two
fermions and one gauge boson could have, for some choices of the parameters of
the model, a non-negligible cross-section. Using a toy model of leptophilic
dark matter, we calculate the constraints on the annihilation cross-section
into two electrons and one weak gauge boson from the PAMELA measurements of the
cosmic antiproton-to-proton flux ratio. Furthermore, we calculate the maximal
astrophysical boost factor allowed in the Milky Way under the assumption that
the leptophilic dark matter particle is the dominant component of dark matter
in our Universe. These constraints constitute very conservative estimates on
the boost factor for more realistic models where the dark matter particle also
couples to quarks and weak gauge bosons, such as the lightest neutralino which
we also analyze for some concrete benchmark points. The limits on the
astrophysical boost factors presented here could be used to evaluate the
prospects to detect a gamma-ray signal from dark matter annihilations at
currently operating IACTs as well as in the projected CTA.Comment: 32 pages; 13 figure
A Tentative Gamma-Ray Line from Dark Matter Annihilation at the Fermi Large Area Telescope
The observation of a gamma-ray line in the cosmic-ray fluxes would be a
smoking-gun signature for dark matter annihilation or decay in the Universe. We
present an improved search for such signatures in the data of the Fermi Large
Area Telescope (LAT), concentrating on energies between 20 and 300 GeV. Besides
updating to 43 months of data, we use a new data-driven technique to select
optimized target regions depending on the profile of the Galactic dark matter
halo. In regions close to the Galactic center, we find a 4.6 sigma indication
for a gamma-ray line at 130 GeV. When taking into account the look-elsewhere
effect the significance of the observed excess is 3.2 sigma. If interpreted in
terms of dark matter particles annihilating into a photon pair, the
observations imply a dark matter mass of 129.8\pm2.4^{+7}_{-13} GeV and a
partial annihilation cross-section of = 1.27\pm0.32^{+0.18}_{-0.28}
x 10^-27 cm^3 s^-1 when using the Einasto dark matter profile. The evidence for
the signal is based on about 50 photons; it will take a few years of additional
data to clarify its existence.Comment: 23 pages, 9 figures, 3 tables; extended discussion; matches published
versio
Loop-induced photon spectral lines from neutralino annihilation in the NMSSM
We have computed the loop-induced processes of neutralino annihilation into
two photons and, for the first time, into a photon and a Z boson in the
framework of the NMSSM. The photons produced from these radiative modes are
monochromatic and possess a clear "smoking gun" experimental signature. This
numerical analysis has been done with the help of the SloopS code, initially
developed for automatic one-loop calculation in the MSSM. We have computed the
rates for different benchmark points coming from SUGRA and GMSB soft SUSY
breaking scenarios and compared them with the MSSM. We comment on how this
signal can be enhanced, with respect to the MSSM, especially in the low mass
region of the neutralino. We also discuss the possibility of this observable to
constrain the NMSSM parameter space, taking into account the latest limits from
the FERMI collaboration on these two modes.Comment: 18 pages, 3 figures. Minor clarifications added in the text. Typing
mistakes and references corrected. Matches published versio
Gravitino Dark Matter in Tree Level Gauge Mediation with and without R-parity
We investigate the cosmological aspects of Tree Level Gauge Mediation, a
recently proposed mechanism in which the breaking of supersymmetry is
communicated to the soft scalar masses by extra gauge interactions at the tree
level. Embedding the mechanism in a Grand Unified Theory and requiring the
observability of sfermion masses at the Large Hadron Collider, it follows that
the Lightest Supersymmetric Particle is a gravitino with a mass of the order of
10 GeV. The analysis in the presence of R-parity shows that a typical Tree
Level Gauge Mediation spectrum leads to an overabundance of the Dark Matter
relic density and a tension with the constraints from Big Bang Nucleosynthesis.
This suggests to relax the exact conservation of the R-parity. The underlying
SO(10) Grand Unified Theory together with the bounds from proton decay provide
a rationale for considering only bilinear R-parity violating operators. We
finally analyze the cosmological implications of this setup by identifying the
phenomenologically viable regions of the parameter space.Comment: 28 pages, 5 figures. References added. To appear in JHE
Galactic-Centre Gamma Rays in CMSSM Dark Matter Scenarios
We study the production of gamma rays via LSP annihilations in the core of
the Galaxy as a possible experimental signature of the constrained minimal
supersymmetric extension of the Standard Model (CMSSM), in which
supersymmetry-breaking parameters are assumed to be universal at the GUT scale,
assuming also that the LSP is the lightest neutralino chi. The part of the
CMSSM parameter space that is compatible with the measured astrophysical
density of cold dark matter is known to include a stau_1 - chi coannihilation
strip, a focus-point strip where chi has an enhanced Higgsino component, and a
funnel at large tanb where the annihilation rate is enhanced by the poles of
nearby heavy MSSM Higgs bosons, A/H. We calculate the total annihilation rates,
the fractions of annihilations into different Standard Model final states and
the resulting fluxes of gamma rays for CMSSM scenarios along these strips. We
observe that typical annihilation rates are much smaller in the coannihilation
strip for tanb = 10 than along the focus-point strip or for tanb = 55, and that
the annihilation branching ratios differ greatly between the different dark
matter strips. Whereas the current Fermi-LAT data are not sensitive to any of
the CMSSM scenarios studied, and the calculated gamma-ray fluxes are probably
unobservably low along the coannihilation strip for tanb = 10, we find that
substantial portions of the focus-point strips and rapid-annihilation funnel
regions could be pressured by several more years of Fermi-LAT data, if
understanding of the astrophysical background and/or systematic uncertainties
can be improved in parallel.Comment: 33 pages, 12 figures, comments and references added, version to
appear in JCA
Comparison of the Airtraq® and Truview® laryngoscopes to the Macintosh laryngoscope for use by Advanced Paramedics in easy and simulated difficult intubation in manikins
<p>Abstract</p> <p>Background</p> <p>Paramedics are frequently required to perform tracheal intubation, a potentially life-saving manoeuvre in severely ill patients, in the prehospital setting. However, direct laryngoscopy is often more difficult in this environment, and failed tracheal intubation constitutes an important cause of morbidity. Novel indirect laryngoscopes, such as the Airtraq<sup>® </sup>and Truview<sup>® </sup>laryngoscopes may reduce this risk.</p> <p>Methods</p> <p>We compared the efficacy of these devices to the Macintosh laryngoscope when used by 21 Paramedics proficient in direct laryngoscopy, in a randomized, controlled, manikin study. Following brief didactic instruction with the Airtraq<sup>® </sup>and Truview<sup>® </sup>laryngoscopes, each participant took turns performing laryngoscopy and intubation with each device, in an easy intubation scenario and following placement of a hard cervical collar, in a SimMan<sup>® </sup>manikin.</p> <p>Results</p> <p>The Airtraq<sup>® </sup>reduced the number of optimization manoeuvres and reduced the potential for dental trauma when compared to the Macintosh, in both the normal and simulated difficult intubation scenarios. In contrast, the Truview<sup>® </sup>increased the duration of intubation attempts, and required a greater number of optimization manoeuvres, compared to both the Macintosh and Airtraq<sup>® </sup>devices.</p> <p>Conclusion</p> <p>The Airtraq<sup>® </sup>laryngoscope performed more favourably than the Macintosh and Truview<sup>® </sup>devices when used by Paramedics in this manikin study. Further studies are required to extend these findings to the clinical setting.</p
Comparison of the Airtraq® and Truview® laryngoscopes to the Macintosh laryngoscope for use by Advanced Paramedics in easy and simulated difficult intubation in manikins
<p>Abstract</p> <p>Background</p> <p>Paramedics are frequently required to perform tracheal intubation, a potentially life-saving manoeuvre in severely ill patients, in the prehospital setting. However, direct laryngoscopy is often more difficult in this environment, and failed tracheal intubation constitutes an important cause of morbidity. Novel indirect laryngoscopes, such as the Airtraq<sup>® </sup>and Truview<sup>® </sup>laryngoscopes may reduce this risk.</p> <p>Methods</p> <p>We compared the efficacy of these devices to the Macintosh laryngoscope when used by 21 Paramedics proficient in direct laryngoscopy, in a randomized, controlled, manikin study. Following brief didactic instruction with the Airtraq<sup>® </sup>and Truview<sup>® </sup>laryngoscopes, each participant took turns performing laryngoscopy and intubation with each device, in an easy intubation scenario and following placement of a hard cervical collar, in a SimMan<sup>® </sup>manikin.</p> <p>Results</p> <p>The Airtraq<sup>® </sup>reduced the number of optimization manoeuvres and reduced the potential for dental trauma when compared to the Macintosh, in both the normal and simulated difficult intubation scenarios. In contrast, the Truview<sup>® </sup>increased the duration of intubation attempts, and required a greater number of optimization manoeuvres, compared to both the Macintosh and Airtraq<sup>® </sup>devices.</p> <p>Conclusion</p> <p>The Airtraq<sup>® </sup>laryngoscope performed more favourably than the Macintosh and Truview<sup>® </sup>devices when used by Paramedics in this manikin study. Further studies are required to extend these findings to the clinical setting.</p
Search for dark matter signals with Fermi-LAT observation of globular clusters NGC 6388 and M 15
The globular clusters are probably good targets for dark matter (DM) searches
in -rays due to the possible adiabatic contraction of DM by baryons. In
this work we analyse the three-year data collected by {\it Fermi} Large Area
Telescope of globular clusters NGC 6388 and M 15 to search for possible DM
signals. For NGC 6388 the detection of -ray emission was reported by
{\it Fermi} collaboration, which is consistent with the emission of a
population of millisecond pulsars. The spectral shape of NGC 6388 is also shown
to be consistent with a DM contribution if assuming the annihilation final
state is . No significant -ray emission from M 15 is
observed. We give the upper limits of DM contribution to -ray emission
in both NGC 6388 and M 15, for annihilation final states , ,
, and monochromatic line. The constraints are
stronger than that derived from observation of dwarf galaxies by {\it Fermi}.Comment: 17 pages, 6 figures, accepted by JCA
Investigating Gamma-Ray Lines from Dark Matter with Future Observatories
We study the prospects for studying line features in gamma-ray spectra with
upcoming gamma-ray experiments, such as HESS-II, the Cherenkov Telescope Array
(CTA), and the GAMMA-400 satellite. As an example we use the narrow feature at
130 GeV seen in public data from the Fermi-LAT satellite. We found that all
three experiments should be able to confidently confirm or rule out the
presence of this 130 GeV feature. If it is real, it should be confirmed with a
confidence level higher than 5 sigma. Assuming it to be a spectral signature of
dark matter origin, GAMMA-400, thanks to a projected energy resolution of about
1.5% at 100 GeV, should also be able to resolve both the \gamma\gamma-line and
a corresponding Z\gamma- or H\gamma-feature, if the corresponding branching
ratio is comparable to that into two photons. It will also allow to distinguish
between a gamma-ray line and the similar feature resulting from internal
bremsstrahlung photons.Comment: 12 pages, 6 figures, 1 tabl
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