Feasibility of detecting B8 solar neutrinos at JUNO

Abstract

The Jiangmen Underground Neutrino Observatory (JUNO) features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector. In this talk we describe in detail a comprehensive assessment of JUNO's potential for detecting $^8$B solar neutrinos via the neutrino-electron elastic scattering process. A reduced 2 MeV threshold for the recoil electron energy is achievable with optimized background reduction strategies. With ten years of data taking, about 60,000 signal and 30,000 background events are expected. This leads to a simultaneous measurement of $sin^{2}\theta_{12}$ and $\Delta m^2_{21}$ using reactor antineutrinos and solar neutrinos in the JUNO detector. This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter. If $\Delta m^2_{21}=4.8\times 10^{-5}(7.5\times 10^{-5}eV^2)$, JUNO can provide evidence of neutrino oscillation in the Earth at approximately the 3$\sigma$ (2$\sigma$) level by measuring the non-zero signal rate variation with respect to the solar zenith angle. Moreover, JUNO can simultaneously measure $\Delta m^2_{21}$ using $^8$B solar neutrinos to a precision of 20% or better, depending on the central value, and to sub-percent precision using reactor antineutrinos. A comparison of these two measurements from the same detector will help understand the current mild inconsistency between the value of reported by solar neutrino experiments and the KamLAND experiment.