Observing the Migdal effect from nuclear recoils of neutral particles with liquid xenon and argon detectors

TL;DR

This paper investigates the feasibility of experimentally observing the Migdal effect in liquid xenon and argon detectors, aiming to reduce theoretical uncertainties and improve calibration for dark matter detection.

Contribution

It provides a first feasibility study and proof-of-concept calculations for detecting the Migdal effect using low-energy neutrons in xenon and argon detectors.

Findings

Low-energy neutron sources are promising for observing the Migdal effect.

Detection requires modest neutron flux, detector size, and exposure.

The study guides future experimental efforts in dark matter searches.

Abstract

In recent years, dark matter direct detection experiments have spurred interest in the Migdal effect, where it is employed to extend their sensitivity to lower dark matter masses. Given the lack of observation of the Migdal effect, the calculation of the signal is subject to large theoretical uncertainties. It is therefore desirable to attempt a first measurement of the Migdal effect, and to test the theoretical predictions of the Migdal effect for the calibration of the experimental response to a potential dark matter signal. In this work, we explore the feasibility of observing the Migdal effect in xenon and argon. We carry out proof-of-concept calculations for low-energy neutrons from a filtered source, and using a reactor, the Spallation Neutron Source, or $^{51}$Cr as potential neutrino sources. We perform a detector simulation for the xenon target and find that, with available technology, the low-energy neutron source is the most promising, requiring only a modest neutron flux, detector size, and exposure period.