Measurement of the 8B Solar Neutrino Flux with the KamLAND Liquid Scintillator Detector

TL;DR

This paper reports a precise measurement of 8B solar neutrino flux using KamLAND's liquid scintillator, confirming consistency with Standard Solar Model predictions and neutrino oscillation effects.

Contribution

First measurement of 8B solar neutrino flux with KamLAND's liquid scintillator, achieving high precision and background control.

Findings

Measured flux of 2.77±0.26(stat)±0.32(syst) x 10^6 cm^-2s^-1

Results are consistent with Standard Solar Model predictions

Background from cosmogenic isotopes is the main systematic uncertainty

Abstract

We report a measurement of the neutrino-electron elastic scattering rate from 8B solar neutrinos based on a 123 kton-day exposure of KamLAND. The background-subtracted electron recoil rate, above a 5.5 MeV analysis threshold is 1.49+/-0.14(stat)+/-0.17(syst) events per kton-day. Interpreted as due to a pure electron flavor flux with a 8B neutrino spectrum, this corresponds to a spectrum integrated flux of 2.77+/-0.26(stat)+/-0.32(syst) x 10^6 cm^-2s^-1. The analysis threshold is driven by 208Tl present in the liquid scintillator, and the main source of systematic uncertainty is due to background from cosmogenic 11Be. The measured rate is consistent with existing measurements and with Standard Solar Model predictions which include matter enhanced neutrino oscillation.