$^7$Be + p and $^3$He + $^4$He fusion reactions and neutrino astrophysics*

The $^7$Be + p and $^3$He + $^4$He fusion reactions are important steps in the solar p-p chain that lead to the production of neutrinos from decay of $^8$B and $^7$Be in the Sun. Until recently the uncertainty in the $^7$Be + p S-factor was the largest error in the calculated solar model production rate of neutrinos from $^8$B decay, while now it is no longer important [1,2]. The uncertainty in the $^3$He + $^4$He S-factor is now the largest nuclear physics uncertainty in the calculated solar model production rate of neutrinos from both $^8$B and $^7$Be decay [2]. I will discuss the current status of these fusion experiments and the implications for neutrino physics including limits on sterile neutrinos. \newline \newline [1] A. R. Junghans et al., Phys. Rev. C 68, 065803 (2003). \newline [2] J. N. Bahcall and M. H. Pinsonneault, Phys. Rev. Lett. 92, 121301 (2004).