Berlin 2005 – scientific programme
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HK: Physik der Hadronen und Kerne
HK 38: Kernphysik/Spektroskopie
HK 38.6: Talk
Wednesday, March 9, 2005, 15:30–15:45, TU MA004
Measurement of the nuclear matrix elements for 0νββ decay — •E.-W. Grewe, C. Bäumer, D. Frekers, S. Hollstein, and S. Rakers — Institut für Kernphysik, WWU Münster
The double beta decay is a rare second-order weak transition. A nucleus can undergo double beta decay with or without emission of neutrinos. The 0ν-mode is only possible if the neutrinos are massive Majorana particles or not purely left-handed. This mode is of great interest for neutrino-mass estimations, however the nuclear matrix element is needed to connect a measured half-life to the neutrino mass.
The nuclear matrix element can be calculated if the complete set of Gamow-Teller (GT) matrix elements for the two virutal transitions in the perturbative description are known. While for the 2ν mode only allowed GT transitions play a role, the 0ν mode rather proceeds through forbidden, i.e. higher multipole, transitions. An elegant way to experimentally obtain GT distributions are charge-exchange reactions. If transitions beyond the allowed GT ones have to be studied, high energy resolution spectra and angular distributions are necessary to precisely identify single excitations. We present new 48Ca(3He,t) data taken at RCNP (Osaka, Japan) [1] which have energy resolutions of 40 keV so that the multipolarity of all low-lying states can be studied. Comparisons with theoretical calculations are presented. The data is combined with high-resolution 48Ti(d,2He) data [2] to obtain 2νββ half-lives.
[1] H. Fujita et al., Nucl. Instr. Meth. A 484, 17 (2002).
[2] S. Rakers et al., Phys. Rev. C 70, 054302 (2004).