Measurement of E1 and E2 cross sections of the $^{12}$C(alpha,gamma)$^{16}$O reaction at E$_{eff}$=1.4 MeV

The gamma-ray angular distribution from $^{12}$C(alpha,gamma)$^{16}$O to the ground state of $^{16}$O was measured using a pulsed alpha beam at $E_{eff}$=1.6 and 1.4 MeV. True gamma-ray events of $^{12}$C(alpha,gamma)$^{16}$O were obtained by discriminating backgrounds due to neutrons from $^{13}$C(alpha$,$n)$^{16}$O with a time-of-flight method. A Rutherford backscattering spectrum of alpha particles from enriched $^{12}$C targets was measured during beam irradiation. The astrophysical S factors for E1 and E2 derived from the present cross sections are discussed in comparison with the values derived by the recent R-matrix calculation.