Measurement of the beta-neutrino correlation of sodium-21 usingshakeoff electrons
The beta-neutrino correlation coefficient, a_beta nu, ismeasured in 21Na by detecting the time-of-flight of the recoil nucleusdetected in coincidence with the atomic electrons shaken off in betadecay. The sample of 21Na is confined in a magneto-optic trap. Highdetection efficiency allows low trap density, which suppresses thephotoassociation of molecular sodium, which can cause a large systematicerror. Suppressing the fraction of trapped atoms in the excited stateusing a dark trap also reduces the photoassociation process, and datataken with this technique are consistent. The main remaining systematicuncertainties come from the measurement of the position and size of theatom trap, and the subtraction of background. We find mbox a_betanu=0.5502(60), in agreement with the Standard Model prediction of mboxa_beta nu=0.553(2), and disagreeing with a previous measurement which wassusceptible to an error introduced by the presence of molecularsodium.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director. Office of Science. NuclearPhysics
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 929061
- Report Number(s):
- LBNL-63797; R&D Project: NWEAK; BnR: KB0401022; TRN: US0803460
- Journal Information:
- Physical Review C, Vol. 77; Related Information: Journal Publication Date: 2008
- Country of Publication:
- United States
- Language:
- English
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