146 research outputs found

    Dark matter, extra-terrestrial gamma-rays and the MSSM: a viability study

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    We fit the γ\gamma-ray excess from the galactic centre (GC) in terms of parameters of the minimal supersymmetric standard model (MSSM). Consistency with other γ\gamma-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 χmin2\chi^2_{min} as well as pp-values. In some case(s), the unacceptability of low-χmin2\chi^2_{min} regions due to direct search constraint is responsible for this. In others, the observed shape of the γ\gamma-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 γ\gamma-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

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    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

    Atom photon interfaces using fabricated spherical mirrors

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    Ph.DDOCTOR OF PHILOSOPH

    CFT reconstruction of local bulk operators in half-Minkowski space

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    We construct a holographic map that reconstructs massless fields (scalars, Maxwell field \& Fierz-Pauli field) in half-Minkowski spacetime in d+1d+1 dimensions terms of smeared primary operators in a large NN factorizable CFT in Rd1,1\mathbb{R}^{d-1,1} 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

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    Relativistic axions produced in decays of O(107102{\mathcal O}(10^{-7}-10^{-2} eV)\text{eV}) 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 ×\times 101310^{-13} 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

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    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 e+ee^+ e^--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 γ\gamma-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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