147 research outputs found
Dark matter, extra-terrestrial gamma-rays and the MSSM: a viability study
We fit the -ray excess from the galactic centre (GC) in terms of
parameters of the minimal supersymmetric standard model (MSSM). Consistency
with other -ray observation, such as those from dwarf spheroidal
galaxies, is also ensured, in addition to the constraints from direct dark
matter search. Furthermore, we expect the contribution to the relic density
from the MSSM dark mater candidate, namely, the lightest neutralino, should not
go below the stipulated value; otherwise it will amount to going beyond the
MSSM by including some additional dark matter source. After a detailed scan of
the parameter space in terms of four representative types of particle spectra,
we identify the ones that are best fit to the observed data. However, these two
are somewhat unsatisfactory in terms of as well as -values.
In some case(s), the unacceptability of low- regions due to
direct search constraint is responsible for this. In others, the observed shape
of the -ray spectrum makes the fits unsatisfactory. The imposed lower
limit on relic density, too, has a role to play all along. On the whole, the
conclusion is that the MSSM is not a very satisfactory fit for the GC
-ray compounded with other cosmological observations and direct search
limits.Comment: 40 pages, 16 figures: figures corrected, typos corrected, matches
with version published in JCA
Trapping and detection of single atoms using a spherical mirror
We fabricate a miniature spherical mirror for tightly focusing an optical
dipole trap for neutral atoms. The mirror formation process is modelled to
predict the dimensions for particular fabrication parameters. We integrate the
spherical mirror with a neutral atom experiment to trap and detect a single
atom with high efficiency. The mirror serves the dual purpose of focusing the
dipole trap as well as collection of the atomic fluorescence into an optical
fibre.Comment: 13 pages, 6 figure
CFT reconstruction of local bulk operators in half-Minkowski space
We construct a holographic map that reconstructs massless fields (scalars,
Maxwell field \& Fierz-Pauli field) in half-Minkowski spacetime in
dimensions terms of smeared primary operators in a large factorizable CFT
in spacetime dimensions. This map is based on a Weyl
(rescaling) transformation from the Poincar\'e wedge of AdS to the Minkowski
half-space; and on the HKLL smearing function, which reconstructs local bulk
operators in the Poincar\'e AdS in terms of smeared operators on the conformal
boundary of the Poincar\'e wedge. The massless scalar field is reconstructed up
to the level of two-point functions, while the Maxwell field and massless
spin-2 fields are reconstructed at the level of the one-point function. We also
discuss potential ways the map can be generalized to higher dimensions, and to
the full Minkowski space.Comment: Updated bibliography, Updated discussion section, 20 pages, 2 figure
Searching for relativistic axions in the sky
Relativistic axions produced in decays of
dark matter (DM) partially convert to photons after traversing the
galactic magnetic field, giving rise to a signal observable by the Square
Kilometer Array (SKA) radio telescope. We show that for axions lighter than a
few eV a 100\,h SKA observation of the local dwarf galaxy
Seg I would probe parameter space not constrained by stellar cooling and
cosmological observations, with sensitivity several orders of magnitude better
than the planned dedicated axion dark matter search experiments. We quantify
the uncertainties in the SKA sensitivity projections due to two effects that
enhance the photon flux: the presence of turbulent magnetic fields inside the
galaxy, and the Bose enhancement of the DM decays to axions, where the latter,
in particular, warrants further study.Comment: 24 pages, 12 figure
Heavy dark matter particle annihilation in dwarf spheroidal galaxies: radio signals at the SKA telescope
A weakly interacting dark matter candidate is very difficult to detect at
high-energy colliders like the LHC, if its mass is close to, or higher than, a
TeV. We argue that the pair-annihilation of such particles may give rise to
-pairs in dwarf spheroidal galaxies (dSph), which in turn can lead to
radio synchrotron signals that are detectable at the upcoming square kilometre
array (SKA) telescope within a fairly moderate observation time. We investigate
in detail the underlying mechanisms that make this possible. Both particle
physics issues and those pertaining to astrophysics, such as diffusion,
electromagnetic energy loss and the effects of interstellar magnetic field, are
examined with reference to their roles in generating radio flux. We first
identify the detectability criteria in a model-independent manner. It is
observed that fluxes may be detectable for scenarios that are consistent with
all constraints available till date from -ray and cosmic-ray
observations. Thereafter, using benchmarks based on popular scenarios involving
physics beyond the standard model, we show that it should be possible to detect
the radio flux from a dSph like Draco with 100 hours of observation at the SKA,
for dark matter particle masses upto 4-8 TeV. The corresponding frequency
distributions are also presented, where it is found that the frequency range
300 MHz - 50 GHz is especially useful for recording the annihilation signals of
trans-TeV particles.Comment: 27 pages, 14 figure
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