The (d,2He) reaction on 76Se and the double-β-decay matrix elements for A=76

The (d,He-2) charge-exchange reaction on Se-76 was studied at an incident energy of 183 MeV. The outgoing two protons in the S-1(0) state, referred to as He-2, were both momentum analyzed and detected by the same spectrometer and detector. The experiment was performed at KVI, Groningen, using the magnetic spectrometer BBS at three angular positions: 0(degrees),2.5(degrees), and 5(degrees). Excitation-energy spectra of the residual nucleus As-76 were obtained with an energy resolution of about 120 keV (FWHM). Gamow-Teller (GT(+)) transition strengths were extracted up to 5 MeV and compared with those from an (n,p) experiment at low resolution. Together with the GT(-) transition strengths from the Ge-76(p,n) experiment leading to the same intermediate nucleus, the nuclear matrix element of the two-neutrino double-beta decay of Ge-76 was evaluated.