Solar neutrino-electron scattering as background limitation for double beta decay

TL;DR

This paper calculates the background noise from solar neutrino-electron scattering in double beta decay experiments, highlighting its impact on future detector sensitivity and the challenges it poses for different experimental approaches.

Contribution

It provides a detailed estimation of solar neutrino-induced background levels for various double beta decay emitters and discusses implications for next-generation experiments.

Findings

Background level is [1-2]E-7 counts/keV/kg/yr for Q-values above 2 MeV.

Background increases significantly at lower Q-values.

Loaded liquid scintillator experiments face higher background challenges.

Abstract

The background on double beta decay searches due to elastic electron scattering of solar neutrinos of all double beta emitters with Q-value larger than 2 MeV is calculated, taking into account survival probability and flux uncertainties of solar neutrinos. This work determines the background level to be [1-2]E-7 counts /keV/kg/yr, depending on the precise Q-value of the double beta emitter. It is also shown that the background level increases dramatically if going to lower Q-values. Furthermore, studies are done for various detector systems under consideration for next generation experiments. It was found that experiments based on loaded liquid scintillator have to expect a higher background. Within the given nuclear matrix element uncertainties any approach exploring the normal hierarchy has to face this irreducible background, which is a limitation on the minimal achievable background for purely calorimetric approaches. Large scale liquid scintillator experiments might encounter this problem already while exploring the inverted hierarchy. Potential caveats by using more sophisticated experimental setups are also discussed.