A measurement of parity-violating gamma-ray asymmetries in polarized cold neutron capture on 35Cl, 113Cd, and 139La

Abstract

An apparatus for measuring parity-violating asymmetries in gamma-ray emission following polarized cold neutron capture was constructed as a 1/10th scale test of the design for the forthcoming n+p->d+gamma experiment at LANSCE. The elements of the polarized neutron beam, including a polarized 3He neutron spin filter and a radio frequency neutron spin rotator, are described. Using CsI(Tl) detectors and photodiode current mode readout, measurements were made of asymmetries in gamma-ray emission following neutron capture on 35Cl, 113Cd, and 139La targets. Upper limits on the parity-allowed asymmetry $s_n\cdot (k_{\gamma }\times k_n)$ were set at the level of 7 x 10^-6 for all three targets. Parity-violating asymmetries $s_n\cdot k_{\gamma }$ were observed in 35Cl, A_gamma = (-29.1 +- 6.7) x 10^-6, and 139La, A_gamma = (-15.5 +- 7.1) x 10^-6, values consistent with previous measurements.

arXiv comment19 pages, 4 figures, submitted to Nucl. Instr. and Meth. A

References in corpus (3)

• Consistency of parity-violating pion-nucleon couplings extracted from measurements in 18F and 133Cs
• Parity conserving gamma asymmetry in n-p radiative capture
• Progress toward a new measurement of the parity violating asymmetry in n+p-->d+gamma

Cited by in corpus (8)

• Experiments in Fundamental Neutron Physics
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• High-Efficiency Resonant RF Spin Rotator with Broad Phase Space Acceptance for Pulsed Polarized Cold Neutron Beams
• A Current Mode Detector Array for Gamma-Ray Asymmetry Measurements
• Upper Bounds on Parity Violating Gamma-Ray Asymmetries in Compound Nuclei from Polarized Cold Neutron Capture
• Monte Carlo calculation and verification of the geometrical factors for the NPDGamma experiment
• Measurement of the Parity-Odd Angular Distribution of Gamma Rays From Polarized Neutron Capture on ${}^{35}$Cl
• Monte Carlo calculation of the average neutron depolarization for the NPDGamma experiment