Low-energy (anti)neutrino physics with Borexino: Neutrinos from the primary proton-proton fusion process in the Sun

TL;DR

This paper reports the first direct spectral measurement of neutrinos from the primary proton-proton fusion process in the Sun, providing key insights into solar core reactions and neutrino oscillations.

Contribution

It presents the first direct spectral detection of pp-chain neutrinos, advancing solar neutrino spectroscopy and validating the LMA-MSW neutrino oscillation model.

Findings

First direct spectral measurement of pp neutrinos

Confirmation of solar core fusion processes

Validation of neutrino oscillation models

Abstract

The Sun is fueled by a series of nuclear reactions that produce the energy that makes it shine. The primary reaction is the fusion of two protons into a deuteron, a positron and a neutrino. These neutrinos constitute the vast majority of neutrinos reaching Earth, providing us with key information about what goes on at the core of our star. Several experiments have now confirmed the observation of neutrino oscillations by detecting neutrinos from secondary nuclear processes in the Sun; this is the first direct spectral measurement of the neutrinos from the keystone proton-proton fusion. This observation is a crucial step towards the completion of the spectroscopy of pp-chain neutrinos, as well as further validation of the LMA-MSW model of neutrino oscillations.