Energy dependence of the 7Be(p,γ)8B S factor, and charge symmetry in the 7Li+n and 7Be+p systems

The measured energy dependence of the 7Be(p,γ)8B S factor is fitted better by the cluster-model calculation of Descouvemont and Baye than by other models. It is suggested here that this may be connected with the cluster model predicting too high an absolute value of the S factor. Evidence for a breakdown of charge symmetry between the 7Li+n and 7Be+p systems is discussed and found not to be convincing. R-matrix formulae are used.