Research: dark matter


Weakly Interacting Massive Particles (WIMPs) and axions are two of the best motivated cold matter candidates. WIMPs are generically produced in the early Universe with roughly the required density and supersymmetry provides us with a concrete, well-motivated candidate in the form of the lightest neutralino. Axions arise from the Peccei-Quinn mechanism, proposed to solve the strong CP problem (namely understanding why the electric dipole moment of the neutron is so small). WIMPs and axions can both be detected directly in the lab. WIMPs can elastic scatter off nuclei in dedicated detectors, while axions can be converted into photons in a resonant magnetic cavity.

I have worked extensively on the signals (energy dependence, annual modulation, and
direction dependence) expected in direct detection experiments. With Stefan Hofmann and Dominik Schwarz I studied the micro-physics of WIMPs in the early Universe and calculated the properties of the first, Earth mass, microhalos to form. With former PhD student (now postdoc at GRAPPA, Amsterdam) Bradley Kavanagh, I worked on parameterising the WIMP speed distribution in order to obtain an unbiased measurement of the WIMP mass from future direct detection experiments. With former Leverhulme trust funded postdoc, Mattia Fornasa, I worked on building more realistic self-consistent models of the Milky Way. Another former PhD student (now postdoc in Zaragoza), Ciaran O’Hare, has looked at how directional detection experiments can probe features in the speed distribution and also distinguish WIMPs from neutrino backgrounds. Recently Ciaran and I looked at how a future high resolution ADMX-like experiment could measure the axion velocity distribution, including streams from mini clusters.