Search for electron antineutrino interactions with the Borexino Counting Test Facility at Gran Sasso

TL;DR

This study searched for electron antineutrino interactions with the Borexino CTF, setting an upper limit on solar antineutrino flux and transition probability, and discussing detection prospects including geoneutrinos.

Contribution

First search for solar electron antineutrinos with Borexino CTF, establishing new upper limits and analyzing detection potential for geoneutrinos.

Findings

Upper limit on solar antineutrino flux: 1.1×10^5 cm^-2 s^-1

Transition probability ν_e → ν̅_e: 0.02 (90% C.L.)

Detection predictions for geoneutrinos discussed

Abstract

Electron antineutrino interactions above the inverse beta decay energy of protons ($E_\bar{\nu}_e>$1.8) where looked for with the Borexino Counting Test Facility (CTF). One candidate event survived after rejection of background, which included muon-induced neutrons and random coincidences. An upper limit on the solar $\bar{\nu}_{e}$ flux, assumed having the $^8$B solar neutrino energy spectrum, of 1.1$\times10^{5}$ cm$^{-2}$~s$^{-1}$ (90% C.L.) was set with a 7.8 ton $\times$ year exposure. This upper limit corresponds to a solar neutrino transition probability, $\nu_{e} \to \bar{\nu}_{e}$, of 0.02 (90% C.L.). Predictions for antineutrino detection with Borexino, including geoneutrinos, are discussed on the basis of background measurements performed with the CTF.