Weak pion-nucleon coupling strength: New constraint from parity mixing in /sup 18/F

Journal Article · Sun Mar 01 04:00:00 EST 1987 · Phys. Rev. C; (United States)

DOI:https://doi.org/10.1103/PhysRevC.35.1119· OSTI ID:5944156

Page, S A; Evans, H C; Ewan, G T; Kwan, S H; Leslie, J R; MacArthur, J D; McLatchie, W; Skensved, P; Wang, S H; Mak, H H

The circular polarization of the 1.081 MeV ..gamma.. rays from /sup 18/F has been measured to be (1.7 +- 5.8) x 10/sup -4/. /sup 18/F was produced by a 4.05 MeV /sup 3/He/sup +/ beam impinging on a recirculating water target with a thin entrance window. The circular polarization was measured with four magnetic transmission polarimeters, each backed by a 150 cm/sup 3/ n-type Ge detector. A fast data acquisition system limited overall peak losses to 30% at a count rate of 60 kHz per detector. Supplementary experiments were carried out to investigate the sensitivity of the circular polarization measurement to systematic variations of beam position and intensity. These effects were found to be negligible relative to the statistical uncertainty. The experimental result is interpreted in terms of an isovector parity-nonconserving matrix element between the chemically bond0/sup +/,T = 1,1.042 MeV> and chemically bond0/sup -/,T = 0,1.081 MeV> states in /sup 18/F that is dominated by the weak pion exchange contribution. The present result for the weak pion-nucleon coupling strength is chemically bondf/sub ..pi..//sup 1/chemically bond = (0.4/sub -0.4//sup +1.4/) x 10/sup -7/, which is significantly smaller than recent theoretical predictions based on the Weinberg-Salam model.

• Research Organization: Queen's University, Kingston, Ontario, Canada K7L 3N6
• OSTI ID: 5944156
• Journal Information: Phys. Rev. C; (United States), Journal Name: Phys. Rev. C; (United States) Vol. 35:3; ISSN PRVCA
• Country of Publication: United States
• Language: English

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