Measurement of E2 transitions in the Coulomb dissociation of 8B

In an effort to understand the implications of Coulomb dissociation experiments for the determination of the 7Be(p,γ) 8B reaction rate, longitudinal momentum distributions of 7Be fragments produced in the Coulomb dissociation of 44 and 81 MeV/u8B beams on a Pb target were measured. These distributions are characterized by asymmetries interpreted as the result of interference between E1 and E2 transition amplitudes in the Coulomb breakup. At the lower beam energy, both the asymmetries and the measured cross sections are well reproduced by first order perturbation theory calculations, allowing a determination of the E2 strength. The measurement yields SE2/SE1=6.7−1.9+2.8×10−4 at the 0.63 MeV 1+ resonance. If higher order dynamical effects are not negligible, then the E2 strength extracted here is a lower limit.