Monte Carlo calculation of the average neutron depolarization for the NPDGamma experiment

Abstract

The NPDGamma experiment measures the asymmetry in $\gamma$-ray emission in the capture of polarized neutrons on liquid parahydrogen. The beam polarization is measured using ${}^3$He spin analysis, but this measurement does not account for the contribution of depolarization from spin-flip scattering primarily due to orthohydrogen in the bulk liquid. This is a systematic effect that dilutes the experimental asymmetry and is modeled using Monte Carlo. Methods for tracking neutron spin in MCNPX were developed in order to calculate the average neutron polarization upon capture for use as a multiplicative correction to the measured beam polarization for the NPDGamma experiment.

arXiv comment9 pages, 7 figures

References in corpus (9)

• New measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission
• First Observation of $P$-odd $\gamma$ Asymmetry in Polarized Neutron Capture on Hydrogen
• 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
• Upper Bounds on Parity Violating Gamma-Ray Asymmetries in Compound Nuclei from Polarized Cold Neutron Capture
• 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
• Monte Carlo calculation and verification of the geometrical factors for the NPDGamma experiment