Modeling the Differential Rate for Signal Interactions in Coincidence with Noise Fluctuations or Large Rate Backgrounds

TL;DR

This paper develops a method to accurately calculate the differential rate of dark matter interactions in detectors, accounting for overlaps with noise and background fluctuations, improving sensitivity estimates in low-energy searches.

Contribution

It introduces a novel calculation method for signal rates overlapping with noise, correcting previous overestimations or conservative underestimations in dark matter detection sensitivity.

Findings

Correctly models the impact of noise and background overlaps on signal detection

Shows that detector response can be understood as long as dark matter pileup probability is low

Proposes a practical 'salting' method to account for live time reductions in data analysis

Abstract

The characteristic energy of a relic dark matter interaction with a detector scales strongly with the putative dark matter mass. Consequently, experimental search sensitivity at the lightest masses will always come from interactions whose size is similar to noise fluctuations and low energy backgrounds in the detector. In this paper, we correctly calculate the net change in measured differential rate due to signal interactions that overlap in time with noise and backgrounds, accounting for both periods of time when the signal is coincident with noise/backgrounds and for the decreased amount of time in which only noise/backgrounds occur. Previous experimental searches have not accounted for this second fundamental effect, and thus either vastly overestimate their experimental search sensitivity (very bad) or use ad hoc conservative cuts which can underestimate experimental sensitivity (not ideal). We find that the detector response to dark matter can be trivially and conservatively understood as long as the true probability of dark matter pileup is small. We also show that introducing random events in the continuous raw data stream (a form of ``salting") provides a correct and practical implementation that correctly accounts for the decreased live time available for noise fluctuations and background events out of coincidence with a true dark matter signal.