Li6(He3,t)Reaction and the Solar Neutrino Puzzle

A search for a ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ + ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ resonance just above threshold was made by means of the reaction ${}_{}{}^6{}_{}{}^{}\mathrm{Li}({}_{}{}^3{}_{}{}^{}\mathrm{He},t){}_{}{}^6{}_{}{}^{}\mathrm{Be}_{}^{*}{}_{}{}^{}$ with 46.3-MeV ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. No resonance was found; the c.m. cross section is ≤1.6 μb/sr at 8.4° c.m. This corresponds to an upper limit on the spectroscopic factor for ${}_{}{}^6{}_{}{}^{}\mathrm{Be}_{}^{*}{}_{}{}^{}\to {}_{}{}^3{}_{}{}^{}\mathrm{He}+{}_{}{}^3{}_{}{}^{}\mathrm{He}$ of 0.0003 to 0.001, depending on the parameters adopted for a distorted-wave Born-approximation calculation. The maximum possible effect of such a resonance on the production of high-energy solar neutrinos is too small to explain the discrepancy between solar-model predictions and the experimental results of Davis et al.