Perspectives for CNO neutrino detection in Borexino

Abstract

Borexino measured with unprecedented accuracy the fluxes of solar neutrinos emitted at all the steps of the pp fusion chain. Still missing is the measurement of the flux of neutrinos produced in the CNO cycle. A positive measurement of the CNO neutrino flux is of fundamental importance for understanding the evolution of stars and addressing the unresolved controversy on the solar abundances. The measurement of the CNO neutrino flux in Borexino is challenging because of the low intensity of this component (CNO cycle accounts for about 1% of the energy emitted by Sun), the lack of prominent spectral features and the presence of background sources. The main background component is 210Bi decaying in the liquid scintillator of Borexino that creates events with an energy distribution very close to the one of CNO neutrino interactions. Since 2015 the collaboration undertook significant efforts to achieve an independent measurement of the background affecting a CNO measurement, whose impact on the sensitivity to a CNO signal will be discussed.