Direct measurements of the

The flux of high energy neutrinos produced in the decay of 8B is proportional to the 7Be(p,γ)8B reaction cross section. Large uncertainties in this cross section limit our ability to test solar models. Direct measurements are underway to reduce the uncertainties to a level of 5% at solar energies. The S17 value seems to converge towards a 19 eV b value instead of 22.4 eV b, which implies a significant reduction (15–20%) in the 8B solar neutrino flux.