Abstract
The double-differential cross sections for the and reactions were measured at 300 MeV. A multipole decomposition technique was applied to the spectra to extract the Gamow-Teller (GT) components. The integrated GT strengths up to an excitation energy of 30 MeV in are and in the and spectra, respectively. In the spectra additional GT strengths were found above 8 MeV where shell models within the shell-model space predict almost no GT strengths, suggesting that the present shell-model description of the nuclear matrix element of the two-neutrino double- decay is incomplete.
- Received 25 March 2009
DOI:https://doi.org/10.1103/PhysRevLett.103.012503
©2009 American Physical Society