One of the source of neutrinos in the Sun is the decay 8 B2 + e +

One of the source of neutrinos in the Sun is the decay ⁸B→2α + e⁺ + ν_e. The boron neutrinos dominate the energy spectrum around 10 MeV. Consider the energy interval 9 MeV < E_ν < 11 MeV. In absence of oscillations their flux at the Earth should be Φ =10¹⁰ m^–2s^–1. The Super-Kamiokande detector is a 22.5 ktfiducial mass water Cherenkov detector in the Kamioka underground observatory.It detects these neutrinos by observing the electron produced in the elastic scatteringν_e + e^- → ν_e + e^-. Assume the cross-section σ (ν_ee) = 10^-47 m² and a detection efficiency ε = 50%. How many events per year are expected? How much is the observed rate in comparison? What is the reason for the difference, if there is one?