XENON1T observes tritium

TL;DR

XENON1T detected an excess of low-energy electron recoil events, potentially caused by tritium decay, suggesting the need for improved gas purification to confirm and mitigate this background.

Contribution

The paper investigates the source of the excess events in XENON1T, proposing tritium decay as a plausible explanation and highlighting the importance of gas purification system modifications.

Findings

Cosmogenic activation insufficient to explain excess

Tritium decay is a plausible source of events

Gas purification changes could confirm or remove tritium

Abstract

XENON1T recently reported an excess of low-energy electron recoil events that may be attributable to either new physics or to the radioactive decay of tritium. It is likely that hydrogen is not be effectively removed by the hot zirconium getters deployed in the detector. Cosmogenic activation of the xenon underground is found to be insufficient to describe the observed excess, although gases diffusing out of detector materials from cosmogenic activation on surface may contribute. Changes in the operation of gas purification systems for XENON1T and other liquid nobel gas detectors could both confirm the tritium hypothesis and remove it from the detector.