We calculate the angular distribution and total cross section of the 7 Be fragment emitted in the break up reaction of 8 B on 58 Ni and 208 Pb targets at the subCoulomb beam energy of 25.8 MeV, within the non-relativistic theory of Coulomb excitation with proper three-body kinematics. The relative contributions of the E1, E2 and M 1 multipolarities to the cross sections are determined. The E2 component makes up about 65% and 40% of the 7 Be total cross section for the 58 Ni and 208 Pb targets respectively. We find that the extraction of the astrophysical S-factor, S 17 (0), for the 7 Be(p,γ) 8 B reaction at solar energies from the measurements of the cross sections of the 7 Be fragment in the Coulomb dissociation of 8 B at sub-Coulomb energies is still not free from the uncertainties of the E2 component.KEYWORDS: Coulomb dissociation of 8 B, radiative capture of p and 7 Be, Astrophysical S-factors. PACS NO. 25.70.De, 25.40.Lw, 96.60.Kx * Work supported by EPSRC, UK, grant no. GR/K33026. † E-mail address: shyam@tnp.saha.ernet.in Recently von Schwarzenberg et al. [17] have measured the breakup of 8 B on the 58 Ni target at the beam energy of 25.8 MeV, well below the Coulomb barrier, where the E2 component of the breakup is expected to be dominant. In contrast to the experiments reported in Refs. [10,16] where 7 Be and p were measured in coincidence, these authors detect only the 7 Be fragment. In their analysis of the data, they have used the non-relativistic theory of Coulomb excitation [18] and the radiative capture cross sections of Kim, Park and Kim (KPK) [12] to estimate the E1, E2 and M1 component of the breakup cross sections. However, the final state has been approximated as a two body system by these authors. This implies that the measured angles of 7 Be were equated to those of the 7 Be-p center of mass

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Abstract. Nuclear structure data are of crucial importance in order to address important astrophysical problems such as the origin of chemical elements, the inner working of our Sun, and the evolution of stars. We demonstrate this by investigating the ground state structure of 8 B and 7 Be nuclei within the Skyrme Hartree-Fock framework and by calculating the overlap integral of 8 B and 7 Be wave functions. The latter is used to calculate the astrophysical S factor (S 17 ) for the solar fusion reaction 7 Be(p, γ) 8 B.

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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. IntroductionThe 8 B isotope produced in the Sun via the radiative capture reaction 7 Be(p,γ) 8 B is the principal source of the high energy neutrinos detected in the Super-Kamiokande (SK) and 37 Cl detectors [1]. In fact the calculated rate of events in SK as well as SNO detectors [3] is directly proportional to the rate of this reaction measured in the laboratory at low energies (∼ 20 keV) [3]. Unfortunately, the measured cross sections (at relative energies (E CM ) of [p −7 Be] > 200 keV) disagree in absolute magnitude and the value extracted by extrapolating the data in the region of 20 keV differ from each other by 30-40 %. This makes the rate of the reaction 7 Be(p, γ) 8 B the most poorly known quantity in the entire nucleosynthesis chain leading to the formation of 8 B [4]. It may be noted that the rate of the 7 Be(p,γ) 8 B reaction is usually given in terms of the zero-energy astrophysical S-factor, S 17 (0).The Coulomb dissociation (CD) method provides an alternative indirect way to determine the cross sections for the radiative capture reactions at low energies [5,6,7,8,9]. In this procedure it is assumed that the break-up reaction a+Z → (b+x)+Z proceeds entirely via the electromagnetic interaction; the two nuclei a and Z do not interact strongly. By further assuming that the electromagnetic excitation process [5, 6]) the measured cross-sections of this reaction to those of the radiative capture reaction b + x → a + γ. Thus, the astrophysical S-factors of the radiative capture processes can be determined from the study of break-up reactions under these conditions. However, in the CD of 8 B, the contributions of E2 and M 1 multipolarities can be disproportionately enhanced in certain kinematical regimes [10,11]. Furthermore, interference from the nuclear breakup processes may also be considerable in some regions. Therefore, a ...