UC Santa Cruz
Searching for New Physics with the Fermi Large Area Telescope
- Author(s): Johnson, Arne Christian
- Advisor(s): Ritz, Steve
- et al.
Compelling astronomical evidence suggests that a majority of the matter in the Universe, known as dark matter, is not described by the Standard Model of paricle physics. A popular candidate for the identity of the dark matter is weakly interacting massive particles (WIMPs), which are well-motivated in part because they naturally reproduce the correct dark matter relic density in a standard thermal freeze-out scenario. Moreover, WIMP interactions with Standard Model particles can be used to detect WIMPs experimentally with a variety of complementary techniques. Primordial black holes (PBHs), which could have formed in the early Universe from the collapse of primordial overdensities, are another plausible candidate for dark matter. Detecting Hawking radiation from low-mass PBHs would be a monumental achievement in its own right, and the PBH light curve could be exploited as a probe of other physics beyond the Standard Model. The Fermi Large Area Telescope (Fermi-LAT), which is capable of detecting γ rays over a wide range of energies and across the entire sky, is an excellent instrument for studying both of these dark matter candidates. Techniques for detecting the Hawking radiation from evaporating PBHs are developed, and used to search the Fermi-LAT catalog of γ-ray point sources for PBH candidates.
The phenomenology of a WIMP model with a velocity-dependent annihilation cross-section is discussed, and an analysis of Fermi-LAT data at the Galactic Center is performed to search for the sharp kinematic features in the γ-ray spectrum predicted by the model. The searches return no significant indications of WIMPs or PBHs, and in both cases the nonobservation is used to place constraints on the presence of new physics.