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Friday, March 2nd 2018

12:30 pm:

Semi-annihilation describes processes with an initial state of two dark matter particles, and a final state of one plus standard model states. It is a generic feature of dark matter whenever the symmetry group enforcing stability is not a discrete Z2. Semi-annihilation changes the expected signals in current dark matter searches. With the bounds on standard thermal dark matter becoming very strong, now is the ideal time to ask to what extent those bounds apply to semi-annihilation, and what interesting parameter space remains. In this talk, explore the parameter space in a generic, bottom-up approach. We discuss the subtleties involved with semi-annihilation of fermionic dark matter, the role of additional unstable dark sector particles, and the interplay of semi-annihilation and the non-perturbative Sommerfeld effect. We discuss how semi-annihilation may relate to various anomalies seen in cosmic ray searches. Finally, we use an effective field theory approach to place limits in as model-independent a fashion as possible. We find that current searches are effective for processes with coloured final states, but significant model space for semi-annihilation still remains.

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