Is it possible to determine the S-factor of the hep process from a laboratory experiment?

We discuss the problem of solar hep neutrinos originating from the reaction p + He-3 --> He-4 + e(+) + nu(e), and obtain a relation between the astrop hysical S-factor of the hep process and the cross section of the process e( -) + He-4 --> H-3 + n + nu(e) near threshold. The relation is based on the isotopic invariance of strong interactions. The measurement of the latter c ross section would allow to obtain experimental information on S(hep), the value of which, at the moment, is known only from theoretical calculations. (C) 2000 Elsevier Science B.V. All rights reserved.