Cross sections for the ${}^7\mathrm{Be}(p,\gamma {)}^8\mathrm{B}$ reaction have been measured for $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=0.35\mathrm{}–1.4\mathrm{MeV}$ using radioactive ${}^7\mathrm{Be}$ targets. Two independent measurements carried out with different beam conditions, different targets, and detectors are in excellent agreement. A statistical comparison of these measurements with previous results leads to a restricted set of consistent data. The deduced zero-energy $S$ factor $S\left(0\right)$ is found to be 15%–20% smaller than the previously recommended value. This implies a ${}^8\mathrm{B}$ solar neutrino flux lower than previously predicted in various standard solar models.

• Received 9 June 1997

DOI:https://doi.org/10.1103/PhysRevLett.80.928