Breakup of $^8$B and the $^7$Be($p,γ)^8$B reaction

Abstract

The calculated rate of events in some of the existing solar neutrino detectors is directly proportional to the rate of the $^7$Be($p,γ)^8$B reaction measured in the laboratory at low energies. However, the low-energy cross sections of this reaction are quite uncertain as various measurements differ from each other by 30-40 %. The Coulomb dissociation process which reverses the radiative capture by the dissociation of $^8$B in the Coulomb field of a target, provides an alternate way of accessing this reaction. While this method has several advantages (like large breakup cross sections and flexibility in the kinematics), the difficulties arise from the possible interference by the nuclear interactions, uncertainties in the contributions of the various multipoles and the higher order effects, which should be considered carefully. We review the progress made so far in the experimental measurements and theoretical analysis of the breakup of $^8$B and discuss the current status of the low-energy cross sections (or the astrophysical $S$-factor) of the $^7$Be($p,γ)^8$B reaction extracted therefrom. The future directions of the experimental and theoretical investigations are also suggested.