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

The (d,(2)He) charge-exchange reaction on (76)Se was studied at an incident energy of 183 MeV. The outgoing two protons in the (1)S(0) state, referred to as (2)He, 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 (76)As 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 (76)Ge(p,n) experiment leading to the same intermediate nucleus, the nuclear matrix element of the two-neutrino double-beta decay of (76)Ge was evaluated.