Global fits of axions and WIMPs in astrophysics, cosmology, and particle physics
File(s)
Author(s)
Hoof, Sebastian
Type
Thesis
Abstract
I present my contributions towards constraining dark matter candidates with
global statistical analyses. In particular, I show results for global fits of axion
models and for gamma ray searches in dwarf spheroidal galaxies, looking for
weakly interacting massive particles.
For the former, I consider the scenario where the Peccei-Quinn symmetry
breaks before the end of inflation and the axion’s initial field value is a random
variable. I combine experimental results from astrophysics, cosmology,
and laboratory experiments to yield the most statistically rigorous constraints
on these models to date. This includes Bayesian and frequentist exclusion
regions for the various parameters and models while also considering the
effect of the potentially anomalous cooling in white dwarfs. Using Bayesian
techniques, it is possible to make statements about the parameters and abundance
of axions in this Peccei-Quinn symmetry breaking scenario. As a result,
axions probably make up a sizeable fraction – but not the majority – of dark
matter.
I then revisit different sources of uncertainties on the axion realignment density,
estimating the statistical ones with analytical approximations.
Finally, I combine gamma ray data from 27 dwarf spheroidal galaxies to place
limits on the dark matter annihilation into Standard Model particles. The
analysis carefully includes the uncertainties on the dwarfs’ dark matter content.
The resulting constraints on the cross section are similar to previous
analyses for higher masses, while they are stronger for lower masses. As a
consequence, some of the remaining dark matter explanations of the Galactic
Centre excess can be ruled out.
global statistical analyses. In particular, I show results for global fits of axion
models and for gamma ray searches in dwarf spheroidal galaxies, looking for
weakly interacting massive particles.
For the former, I consider the scenario where the Peccei-Quinn symmetry
breaks before the end of inflation and the axion’s initial field value is a random
variable. I combine experimental results from astrophysics, cosmology,
and laboratory experiments to yield the most statistically rigorous constraints
on these models to date. This includes Bayesian and frequentist exclusion
regions for the various parameters and models while also considering the
effect of the potentially anomalous cooling in white dwarfs. Using Bayesian
techniques, it is possible to make statements about the parameters and abundance
of axions in this Peccei-Quinn symmetry breaking scenario. As a result,
axions probably make up a sizeable fraction – but not the majority – of dark
matter.
I then revisit different sources of uncertainties on the axion realignment density,
estimating the statistical ones with analytical approximations.
Finally, I combine gamma ray data from 27 dwarf spheroidal galaxies to place
limits on the dark matter annihilation into Standard Model particles. The
analysis carefully includes the uncertainties on the dwarfs’ dark matter content.
The resulting constraints on the cross section are similar to previous
analyses for higher masses, while they are stronger for lower masses. As a
consequence, some of the remaining dark matter explanations of the Galactic
Centre excess can be ruled out.
Version
Open Access
Date Issued
2019-05
Date Awarded
2019-12
Copyright Statement
Creative Commons Attribution NonCommercial Licence
Advisor
Scott, Pat
Trotta, Roberto
Sponsor
Imperial College London
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)