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Description
An exciting avenue for placing constraints on properties of dark matter has recently come from the application of an obscure quantum mechanical effect predicted by Arkady Migdal in the 1940’s. In the Migdal effect an atomic nucleus receiving a small kick can result in the emission of an electron. Migdal originally considered the nuclear recoil in α- or β-decay, where the effect has been observed, but recent theoretical work applied to dark matter interactions has not been validated. Nevertheless, a number of experiments recently invoked this effect to improve their sensitivity to dark matter mass by ∼2 orders of magnitude. In this talk I will review the Migdal effect and use the XENON experiment to illustrate its use for dark matter limit setting. Given how these and other applications of the effect are impacting the dark matter landscape, an experimental verification of the effect is very much needed. I will describe a method that proposes to do this in the analogous case of nuclear recoils produced by neutron interactions. This method relies on detecting and reconstructing the ionization tracks in a Migdal event in a low-pressure gas time projection chamber (TPC). Using preliminary measurements made in such a detector I will show data that demonstrates that the effect can indeed be measured. Finally, I will discuss prospects for the discovery of this effect in the coming year.
