A High Sensitivity Search for $\bar{\nu}_{e}$'s from the Sun and Other Sources at KamLAND

TL;DR

This paper reports a high-sensitivity search for electron antineutrinos from the Sun and other sources using KamLAND, setting new upper limits on their flux and testing models of neutrino properties.

Contribution

It provides the first stringent upper limit on solar electron antineutrino flux in the specified energy range using KamLAND data.

Findings

No candidate antineutrino events were observed.

Set an upper limit of 3.7 x 10^2 cm^-2 s^-1 on solar $ar{ u}_e$ flux.

Constraints on neutrino spin-flavor precession and decay models.

Abstract

Data corresponding to a KamLAND detector exposure of 0.28 kton-year has been used to search for $\bar{\nu}_e$'s in the energy range 8.3 MeV $<$ E$_{\bar{\nu}_e}$ $<$ 14.8 MeV. No candidates were found for an expected background of $1.1{\pm}0.4$ events. This result can be used to obtain a limit on $\bar{\nu}_{e}$ fluxes of any origin. Assuming that all $\bar{\nu}_e$ flux has its origin in the Sun and has the characteristic $^8$B solar $\nu_e$ energy spectrum, we obtain an upper limit of 3.7 \times 10$^2$ cm$^{-2}$ s$^{-1}$ (90% C.L.) on the $\bar{\nu}_e$ flux. We interpret this limit, corresponding to $2.8{\times}10^{-4}$ of the Standard Solar Model $^8$B $\nu_e$ flux, in the framework of spin--flavor precession and neutrino decay models.