A step toward CNO solar neutrinos detection in liquid scintillators

TL;DR

This paper proposes a method to identify Bismuth-210 background in liquid scintillator detectors by analyzing Polonium-210 alpha decay over time, enabling earlier detection of CNO solar neutrinos.

Contribution

It introduces a novel approach to determine Bismuth-210 background through Po-210 decay rate evolution, improving CNO neutrino detection prospects.

Findings

Bi-210 background can be inferred from Po-210 decay time evolution.

A Borexino-like detector could detect CNO neutrinos within about 1 year.

Stable alpha detection efficiency is crucial for the method's success.

Abstract

The detection of CNO solar neutrinos in ultrapure liquid scintillator detectors is limited by the background produced by Bismuth-210 nuclei that undergo beta-decay to Polonium-210 with a lifetime equal to about 7 days. Polonium-210 nuclei are unstable and decay with a lifetime equal to about 200 days emitting alpha particles that can be also detected. In this letter, we show that the Bi-210 background can be determined by looking at the time evolution of alpha-decay rate of Po-210, provided that alpha particle detection efficiency is stable over the data acquisition period and external sources of Po-210 are negligible. A sufficient accuracy can be obtained in a relatively short time. As an example, if the initial Po-210 event rate is 2000 cpd/100 ton or lower, a Borexino-like detector could start discerning CNO neutrino signal from Bi-210 background in about 1 yr.