He3+He4 → Be7 astrophysical S factor

We present precision measurements of the He3+He4 → Be7 reaction in the range Ec.m.=0.33 to 1.23 MeV using a small gas cell and detection of both prompt γ rays and Be7 activity. Our prompt and activity measurements are in good agreement within the experimental uncertainty of several percent. We find S(0)=0.595±0.018 keV b from fits of the Kajino theory to our data. We compare our results with published measurements, and we discuss the consequences for Big Bang Nucleosynthesis and for solar neutrino flux calculations. © 2007 The American Physical Society.