Low-energy anti-neutrinos from the Sun

We consider the sensitivity of future neutrino experiments in the low energy region, such as BOREXINO or HELLAZ, to a solar ν̄e signal. We show that, if neutrino conversions within the Sun result in partial polarization of initial solar neutrino fluxes, then a new opportunity arises to observe the ν̄eʹs and thus to probe the Majorana nature of the neutrinos. This is achieved by comparing the slopes of the energy dependence of the differential νe-scattering cross section for different neutrino conversion scenarios. We also show how the νe→ν̄e conversions may take place for low energy solar neutrinos while being unobservable at the Kamiokande and Super-Kamiokande experiments.