MEASUREMENTS OF 2-neutrino-DOUBLE-BETA DECAY MATRIX ELEMENTS: THERE ARE STILL SURPRISES IN NUCLEAR PHYSICS

by D. Frekers (University of Muenster, Germany)

Tuesday 19 Jun 2012, 17:45 → 18:45 Europe/Berlin

Institute for Advanced studies (Faculty club)

The talk will be about high-resolution charge-exchange reactions of (n,p) and (p,n) type at intermediate energies, which directly connect to the nuclear matrix elements in double-beta decay. Here, the (n,p) type reactions are realized through (d,He-2) reactions, where He-2 refers to two protons in a singlet ^1S_0state and where both of these are momentum analyzed and detected by the same spectrometer and detector. These reactions have been developed and performed exclusively at KVI, Groningen (NL). The (p,n) type (He-3, t) reaction was developed at the RCNP facility in Osaka (JP) allowing measurements with a resolution of 30 keV at incident energies of 420 MeV. Using both reaction types one can extract the Gamow-Teller transition strengths B(GT^+) and B(GT-^), which define the two "legs" of the 2 nu beta beta decay matrix elements. The high resolution available in both reactions allows a detailed insight into the excitations of the intermediate odd-odd nuclei and, as will be shown, some rather unexpected features are being unveiled. Special emphasis will be placed on the beta-beta decay nuclei Ge-76, Zr-96, Mo-100 and very recent results will be presented for Te-126, -130 and Xe-136. The talk will also be about future directions using ion traps at the TRIUMF radioactive beam facility to measure ground-state properties of the intermediate odd.