Weaker than the Weak Interaction: Dark Matter and Sterile Neutrinos in Theoretical Extensions of the Standard Model
Final Report Abstract
The fact that 80% of the matter in the Universe — the so-called Dark Matter — are unaccounted for by the established theories of elementary particle physics is one of the greatest mysteries of fundamental physics in the 21st century. In spite of technological quantum leaps, experimental searches for dark matter have so far failed to shed light on its nature. On the other hand, a number of a priori unexpected astronomical observation could be interpreted as signals of dark matter, but a definite proof is still lacking. In view of both, new constraints and potential hints, this DFG project has focused on new theoretical ideas for dark matter as well as novel search strategies. The most important new ideas investigated in this project are • Boosted Dark Matter. Very heavy dark matter particles may decay into significantly lighter and therefore highly boosted new particles, which are observable in neutrino telescopes. This novel possibility of observing certain dark matter candidates has now become the topic of an experimental PhD thesis within the IceCube collaboration. • Lepton Jets from Radiating Dark Matter. Dark matter is usually assumed to be completely invisible to LHC detectors. However, in scenarios in which dark matter particles can interact with each other through a new force (as motivated by some observations of large scale structures in the Universe), dark matter produced at the LHC will be accompanied by a shower of new force mediators, in the same way as production of charged Standard Model particles is accompanied by showers of photons. As the new force mediators will typically decay back to Standard Model particles, this shower can be observed as a collimated set of highly boosted particles. This would make dark matter much less dark than in traditional models, opening up exciting new observational possibilities at colliders. • Dark Gamma Ray Bursts. It is known that stars can gravitationally capture significant numbers of dark matter particles throughout their lives. We demonstrated for the first time that the dark matter bound to the star is significantly compressed in the pre-supernova stage and during the supernova itself, leading to rapid dark matter annihilation on a time scale of minutes. In some dark matter models the resulting signals, which we dubbed “dark gamma ray bursts” could be observable in gamma ray observatories. • Dark Matter–Neutrino Interactions. We have demonstrated that ultra-light dark matter particles (motivated by unexplained features of dwarf galaxies) could interact with neutrinos and alter neutrino oscillation. These effects could be observable in future longbaseline neutrino experiments like DUNE or T2HK. While the physics case of these experiments is traditionally centered around standard three-flavor oscillations, our model offers exciting possibilities to search for new physics. • Annihilating Dark Matter at the keV Scale. Dark matter with mass of order keV is typically assumed to be observable only if it is unstable and decays. We have developed a simple model that features annihilating dark matter at the keV scale. While being very simple, the model explains simultaneously the dark matter abundance in the Universe, observations of large and small scale structure, and it can lead to observable annihilation signals. In particular, it could account for a recently observed, but so far unexplained, line in the x-ray spectrum from galaxies and galaxy clusters. In doing so, the model fares better than previous explanations of the new x-ray line in terms of sterile neutrinos.
Publications
- Fuzzy Dark Matter and Non-Standard Neutrino Interactions (2017)
V. Brdar, J. Kopp, J. Liu, P. Prass, X.-P. Wang
- Boosted Dark Matter in IceCube and at the Galactic Center, JHEP 04, 105 (2015)
J. Kopp, J. Liu, X.-P. Wang
- Lepton Jets from Radiating Dark Matter, JHEP 07, 045 (2015)
M. Buschmann, J. Kopp, J. Liu, P. A. N. Machado
- The Coannihilation Codex, JHEP 12, 120 (2015)
M. J. Baker et al.
- Dark Gamma Ray Bursts, Phys. Rev. D95, 055031 (2017)
V. Brdar, J. Kopp, J. Liu
- Return of the X-rays: A New Hope for Fermionic Dark Matter at the keV Scale (2017)
V. Brdar, J. Kopp, J. Liu, X.-P. Wang
