A thesis submitted to the Department of Physics, University of the Witwatersrand in
fulfilment of the academic requirements of the degree of Doctor of Philosophy. Johannesburg, June 17, 2016. / The nature of dark matter remains one of the most significant problems in modern physics.
One candidate hypothesis with strong theoretical motivation is a WIMP (Weakly Interacting
Massive Particle) in the form of the supersymmetric neutralino. Although this lacks
experimental evidence, supersymmetry may manifest in collider experiments and also has
observable consequences in the emission of annihilation products from cosmic structures
which would play host to large neutralino densities. Historically, interest has been focussed
upon the direct detection of WIMPs, as well as indirect observation through
-rays produced
by pair-annihilation processes. In this work we present a detailed argument for a
multi-frequency observational strategy. We motivate this by studying the redshift evolution
of radio synchrotron radiation emitted by WIMP annihilation-product electrons. In so doing,
we demonstrate the potential power of the SKA to probe the neutralino parameter space,
being able to produce constraints several orders of magnitude better than current limits and
distinguish between differing neutralino masses and annihilation channels. Furthermore,
we motivate the SKA as a machine to study dark matter by discussing its ability to characterise
cosmic magnetic fields through rotation measures and polarimetry, as well as resolve
between non-thermal emissions produced by dark matter and those resulting from strictly
baryonic processes, like star formation. These technical capabilities obviate the central
uncertainties in the study of synchrotron radiation. Additionally, we highlight optimal laboratories
for neutralino detection via the SKA, based on structures that might produce dark
matter emissions with lower background synchrotron radiation. In particular we highlight
galaxies and galaxy clusters at redshifts z 1 and local dwarf spheroidal galaxies. Finally,
we demonstrate the potential of X-rays, through the ASTRO-H mission, to compliment the
SKA in a multi-frequency search. We then demonstrate our multi-frequency approach in
the analysis of several prominent claims of signals compatible with dark matter-induced
emissions. Showing that models designed to account for the AMS-2/Fermi/PAMELA antiparticle
and galactic centre
-ray excesses are incompatible with existing data as well as
demonstrating that a dark matter interpretation of the Reticulum-2
-ray excess is untenable
for a wide range of dark matter particle masses. / LG2017
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/21666 |
| Date | January 2016 |
| Creators | Beck, Geoffrey Martin |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (v, 123 pages), application/pdf |
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