GSI-Kolloquium:"Measurement of the orbital electron capture and of the β+ decay of hydrogen-like ions at the Experimental Storage Ring of GSI"

The periodic time-modulations, found recently in the two-body orbital electron-capture (EC) decay of both, hydrogen-like 140 Pr and 142Pm ions, have been re-investigated for the case of hydrogen-like 142Pm ions by using as Schottky-noise detectors both the previously employed capacitive pick-up and a newly designed 245 MHz resonator-cavity with much improved sensitivity and time resolution. The new results corroborate for both detectors exactly our previous findings of a statistically significant modulation with a period near to 7 seconds, though with distinctly smaller amplitudes. The latter observation is not yet understood. Also the β+ decays have been analyzed which do not show any significant modulation near to 7 seconds. The confirmed observation that periodic modulations are appearing in the EC decay, where monochromatic electron neutrinos are generated, while being absent in the three-body β+ decay with a broad neutrino spectrum, could point at weak interaction and, in particular, at the peculiar features of two-body weak decays as the origin of the oscillations. If the latter is true, then the data furthermore suggest that interference terms are present in the EC decay, although the emerging neutrinos are not directly observed.