Delayed Electron Phenomenology for Ionization Only Searches in XENONnT

The XENONnT experiment has set world leading limits on the interaction strength of WIMP Dark Matter (DM) with ordinary matter, and contributed to many other rare event searches. As sensitivities and exposures continue to increase, the neutrino fog will present more challenges to traditional WIMP searches. Ionization-only searches allow for significantly lowering the energy threshold by not pairing the prompt scintillation signal with the greatly amplified ionization signal. This lowered threshold opens up unexplored parameter space in many light dark matter models.

Delayed Electrons (DE) are single and few electron singals that appear up to 𝒪(s) after larger signals, and present the most challenging background to these types of searches. While the mechanism behind them is still poorly understood, significant progress has been made in a phenomenological study of the detector effects.

We show that DE have positions that are correlated with the previous large signal, and that the degree of correlation is dependent on the integrated area of the delayed signal. Further, a Monte Carlo simulation has been developed, which demonstrates that the vast majority of DE are position correlated. Preliminary results for a complete background model in this energy regime will also be discussed. This model will allow for future results to claim discoveries, since previous results were restricted to limit setting searches.