arXiv subjects

J. W. Paster

Publications and source records attributed to J. W. Paster.

3 recordsLinked to original sources

arXiv2026

Precision measurement of radiative neutron \b{eta}-decay: methodology and systematic effects

In the Standard Model the free neutron decays to a proton, an electron, and an antineutrino along with a continuous spectrum of photons. In 2016 the RDK II collaboration reported on a measurement of the photon energy spectrum and branching ratio over the range of 0.4 keV to the 782 keV endpoint using two different detector arrays. In the experiment, the radiative decay photons were observed in coincidence with the decay electrons and protons. In this paper, we present details of the analysis, including the determination of the systematic corrections and uncertainties and comparison of measured particle and photon energy spectra to Monte Carlo simulations. We conclude with approaches to improving the precision of these measurements.

nucl-ex↗

arXiv2026

Experimental Limit on Neutron Orbital Angular Momentum Detection Using Polarized 3He

A recent proposal suggested that neutron orbital angular momentum (OAM) states could be detected via spin-polarized absorption in polarized 3He, with predicted cross-section variations linked to the neutron's OAM. We experimentally tested this hypothesis using spin-polarized neutron beams with OAM =-2 to 2, generated by fork-dislocation phase-gratings, and transmitted through a polarized 3He cell. Within statistical precision, no OAM-dependent change in the absorption cross section was observed. This null result places stringent constraints on polarized 3He-based OAM detection schemes. The absence of an effect in the given regime is traced to the proposal's disregard of the spatial character of neutron OAM: unlike spin, OAM arises from the transverse phase structure of the wavefunction and couples only through spatial gradients and overlap. The transverse extent of neutron OAM modes expands rapidly, producing a doughnut-shaped intensity profile with negligible overlap with on-axis 3He nuclei, while off-axis capture samples only a locally uniform phase and reduces the interaction to the known spin dependence. These results clarify the limits of absorptive nuclear methods for probing neutron OAM and emphasize the necessity of spatially resolved interactions in any viable detection scheme.

physics.app-ph↗

arXiv2025

Design and Monte Carlo Simulation of a Phase Grating Moir\'e Neutron Interferometer to Measure the Gravitational Constant

The gravitational constant (G) is the least precisely known fundamental constant of nature, with persistent and significant discrepancies between measurement methods. New techniques for measuring G with systematic effects different from commonly applied pendulum methods are required. Neutrons are convenient probes of gravitational forces as they are both massive and electrically neutral, properties that allowed a single-crystal neutron interferometer (NI) to achieve the first experimental demonstration of gravitationally induced quantum interference. Despite this, the limitation of single-crystal NIs to monoenergetic beams significantly reduces neutron flux, making precision gravitational measurements unfeasible. A new NI design called the phase-grating moir\'{e} interferometer (PGMI) has been shown to increase neutron flux by orders of magnitude while allowing grating separation that maintains similar interferometer area to previous NI devices. Here, we propose and describe an experiment to measure G using the PGMI to a precision comparable to measurements from the CODATA 2022 evaluation. A Monte Carlo model for incorporating nonlinear potentials into a PGMI is introduced. This model is used to evaluate sources of systematic uncertainty and quantify the uncertainty in G arising from these effects. The effect of lunar gravitation on a torsion pendulum experiment from CODATA 2022 is calculated, and the need for possible correction factors is demonstrated. This work demonstrates that a neutron PGMI can be used to measure G to $150$ parts-per-million in the near term with the potential to achieve greater precision in future experimental designs.

physics.ins-det↗