Nuclear Physics Input for Solar Models

We discuss microscopic cluster model descriptions of two solar nuclear reactions , 7 Be(p, γ) 8 B and 3 He(3 He, 2p) 4 He. The low-energy reaction cross section of 7 Be(p, γ) 8 B, which determines the high-energy solar neutrino flux, is constrained by 7 Be and 8 B observables. Our results show that a small value of the zero-energy cross section is rather unlikely. In 3 He(3 He, 2p) 4 He we study the effects of a possible virtual state on the cross section. Although, we have found no indication for such a state so far, its existence cannot be ruled out yet. We calculate the 3 He(3 He, 2p) 4 He and 3 H(3 H, 2n) 4 He cross sections in a continuum-discretized coupled channel approximation, and find a good general agreement with the data.