XENON1T excess: Some possible backgrounds

Abstract

This work is a study of some possible background sources in the XENON1T environment which might affect the energy spectrum of electronic recoil events in the lower side and might contribute to the observed excess. We have identified some additional possible backgrounds, like ⁴¹Ca, ⁴⁹V, ⁶³Ni, ¹⁰⁶Ru and ¹²⁵Sb coming from cosmogenic production, where the former two emit monoenergetic X-rays and the latter three have β decays, or isotopes, like ²¹⁰Pb, from the decay chain of ²²²Rn emanated in liquid xenon from the materials, or isotopes, like ¹³⁷Cs, produced due to neutron capture. We perform a ${\chi }^2$ fitting of the ER spectrum from these backgrounds along with tritium to the observed excess events by varying their individual rates to understand whether they can be present to contribute to the low energy excess or their presence is constrained from the data. We also study the possibility of simultaneous presence of more than one such backgrounds, and how this affects the rates required by individual backgrounds to explain the excess.