New sub-barrier nuclear fusion cross sections as a possible solution to the solar neutrino problem

Abstract

The results of the three solar neutrino experiments, Gallex (Gallex coll. 1992a), Homestake (Davis et al. 1990) and Kamiokande-II (Kamiokande-II coll. 1990) indicate the existence of quite tight bounds to the neutrino fluxes produced by the p(p,v _ee⁺)D main initial reaction, and in the ³He(α,γ)⁷Be and ⁷Be(p,γ)⁸B secondary branches. The Solar Standard Model (Bahcall and Pinsonneault 1992) is still significantly far from the limits of the experiments and the hypotheses on non-conventional neutrino properties are strongly disfavoured (Gallex coll. 19926), except for the matter neutrino oscillation (Mikheyev and Smirnov 1986; Wolfenstein 1978), this latter surviving within very narrow limits (Gallex coll. 1992b). The present approach is based on the use of new cross sections for the reactions ³He(³He,2p)α, ³He(α, γ)⁷Be and ⁷Be(p,γ)⁸B, calculated in the framework of the ⨴hadow” model for the sub-barrier fusion (Scalia 1992; Scalia and Figuera 1992). When the standard reaction rates (Caughlan and Fowler 1988) are replaced by those obtained from the new cross sections, the New Solar Model is consistent with the three neutrino experiments and with the internal stratification as deduced from helioseismology.