Bounds on Sterile Neutrino Component in the Solar Neutrino Flux

Abstract

Solar neutrinos studies have played a crucial role in the development of neutrino physics. It took decades to understand the mysterious nature of neutrinos and to identify a leading solution to the Solar Neutrino Problem (SNP). The mystery of the missing neutrinos deepened as subsequent experiments were performed. The energy spectrum of solar neutrinos, as predicted by standard solar models, is seen by different experiments as they are sensitive to different energy ranges. More than 98 \(\%\) of the calculated standard model solar neutrino flux lies below 1MeV. The rare Boron-8 neutrino flux is the high energy tail of solar neutrinos for which statistically significant measurements have been made so far, but this is the tip of the iceberg. As such, the study of low energy neutrinos can give us better understanding and showcase the possibility of species other than three active neutrino flavours, mainly the sterile neutrinos in solar neutrino flux. In the light of latest data available from various solar neutrino experiments including Borexino and KamLAND Solar phase we derive, in a model independent way, the bounds on sterile neutrino component in the solar neutrino flux. We update the limits on the sterile neutrino component and compare them with the previous results obtained using data from SNO Solar Salt Phase and Super-Kamiokande experiments. We retrieve the upper bounds existing in the literature and present the more stringent bounds on the sterile neutrino component.