The Power of the Dark Sink*

Speaker: Robert McGehee (University of Minnesota)

Date: Monday, April 14, 2025

Time: 4:00 – 5:00 pm

Location: 472 Willamette Hall (IFS Seminar Room)

Abstract I will describe a simple dark sector structure which, if present, has implications for the direct detection of dark matter (DM): the Dark Sink. A Dark Sink transports energy density from the DM into light dark-sector states that do not appreciably contribute to the DM density. As an example, I will consider a light, neutral fermion which interacts solely with DM via the exchange of a heavy scalar. I will illustrate the impact of a Dark Sink by adding one to a DM freeze-in model in which DM couples to a light dark photon which kinetically mixes with the Standard Model (SM) photon. I will check the contribution of the Dark Sink to dark radiation; consistency with existing data limits the maximum attainable cross section. For DM with a mass between 30 keV – 30 GeV, adding the Dark Sink can increase predictions for the direct detection cross section all the way up to the current limits.

*Time and interest permitting, I will shift gears for the last third of the talk to discuss an entirely different DM scenario in which WIMP-type DM has additional interactions that break baryon number. This leads to induced nucleon decays which are subject to direct experimental constraints from proton decay experiments. I will analyze the possibility of continuous baryon destruction, deriving strong limits from the dark matter accumulating inside old neutron stars, as such a process leads to excess heat generation.

Host: Ben Lillard