Searches for massive neutrino emission in 14C beta and 55Fe electron-capture decays
- Univ. of California, Berkeley, CA (United States)
In 1985 Simpson reported evidence for the emission of a 17 keV mass neutrino in a small fraction of tritium beta decays. An experimental controversy ensued in which a number of both positive and negative results were reported. The beta spectrum of 14C was collected in a unique 14C-doped planar germanium detector and a distortion was observed that initially confirmed Simpson`s result. Further tests linked this distortion to a splitting of the collected charge between the central detector and the surrounding guard ring in a fraction of the events. A second 14C measurement showed no evidence for emission of a 17 keV mass neutrino. In a related experiment, a high statistics electron-capture internal-bremsstrahlung photon spectrum of 55Fe was collected with a coaxial germanium detector. A local search for departures from a smooth shape near the endpoint was performed, using a second-derivative technique. An upper limit of 0.65% (95% C.L.) for the mixing Of a neutrino in the mass range 5--25 keV was established. The upper limit on the mixing of a 17 keV mass neutrino was 0.14% (95% C.L.).
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Nuclear Physics (NP)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 10174440
- Report Number(s):
- LBL-35568; ON: DE94016863; TRN: 94:015657
- Resource Relation:
- Other Information: TH: Thesis (Ph.D); PBD: May 1994
- Country of Publication:
- United States
- Language:
- English
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