Measurement of the beta-neutrino correlation in laser trapped ²¹Na

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 2003

DOI:https://doi.org/10.2172/821455· OSTI ID:821455

Scielzo, Nicholas David ^[1]

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1. Univ. of California, Berkeley, CA (United States); LBNL Library

Trapped radioactive atoms are an appealing source for precise measurements of the beta-neutrino correlation coefficient, a, since the momentum of the neutrino can be inferred from the detection of the unperturbed low-energy recoil daughter nucleus. Sodium-21 is produced on-line at the 88'' cyclotron at Lawrence Berkeley National Laboratory, and 8e5 atoms have been maintained in a magneto-optical trap. A static electric field draws daughter Neon-21 ions to a microchannel plate detector and betas are detected in coincidence with a plastic scintillator beta detector. The Neon-21 time-of-flight distribution determines the beta neutrino correlation coefficient, a. The resulting charge-state distribution is compared to a simple model based on the sudden approximation which suggests a small but important contribution from nuclear recoil-induced ionization. A larger than expected fraction of the daughters are detected in positive charge-states, but no dependence on either the beta or recoil nucleus energy was observed. We find a = 0.5243 plus or minus 0.0092, which is in 3.6 sigma disagreement with the Standard Model prediction of a = 0.559 plus or minus 0.003. Aside from a deviation from the Standard Model, a possible explanation for the discrepancy is that the branching ratio to the first excited state is in error.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 821455
• Report Number(s): LBNL--54350
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
74 ATOMIC AND MOLECULAR PHYSICS
ATOMS
BRANCHING RATIO
CHARGE STATES
CYCLOTRONS
ELECTRIC FIELDS
EXCITED STATES
FORECASTING
IONIZATION
LASER TRAP MAGNETO OPTICAL TRAP BETA DECAY BETA NEUTRINO CORRELATION
LASERS
NEON 21
NEUTRINOS
PLASTIC SCINTILLATORS
SODIUM 21
STANDARD MODEL
SUDDEN APPROXIMATION