Monte Carlo calculation and verification of the geometrical factors for the NPDGamma experiment

Abstract

The NPDGamma experiment measures the parity-violating asymmetry in $\gamma$-ray emission in the capture of polarized neutrons on liquid parahydrogen. The sensitivity to the asymmetry for each detector in the array is used as a parameter in the extraction of the physics asymmetry from the measured data. The detector array is approximately cylindrically symmetric around the target and a step-wise sinusoidal function has been used for the sensitivity in the previous iteration of the NPDGamma experiment, but deviations from cylindrical symmetry necessitate the use of a Monte Carlo model to determine corrections to the geometrical factors. For the calculations, source code modifications to MCNPX were done in order to calculate the sensitivity of each cesium iodide detector to the physics asymmetry. We describe the MCNPX model and results from calculations and how the results are validated through measurement of the parity violating asymmetry of $\gamma$-rays from neutron capture on chlorine.

arXiv comment10 pages, 10 figures

References in corpus (8)

• New measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission
• Fundamental Neutron Physics Beamline at the Spallation Neutron Source at ORNL
• 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
• A measurement of parity-violating gamma-ray asymmetries in polarized cold neutron capture on 35Cl, 113Cd, and 139La
• Measurement of the absolute neutron beam polarization from a supermirror polarizer and the absolute efficiency of a neutron spin rotator for the NPDGamma experiment using a polarized ${}^3$He neutron spin-filter
• Parity conserving gamma asymmetry in n-p radiative capture
• First results from the NPDGamma experiment at the Spallation Neutron Source

Cited by in corpus (3)

• First Observation of $P$-odd $\gamma$ Asymmetry in Polarized Neutron Capture on Hydrogen
• 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