Setting bounds on a fifth force: Some extensions to the Standard Model of particle physics posit the existence of a fifth force to complement the existing four fundamental forces. To set bounds on the strength of such an interaction, experiments on vastly different length scales have been performed. Heacock et al . used an unusual method called Pendellösung interferometry to measure the neutron structure factors of silicon. The momentum dependence of the structure factors enabled the researchers to put more stringent bounds on the strength of a type of fifth force called the Yukawa force, as well as measure the charge radius of the neutron. —JS

An $sp$-mixing model, which describes a compound nuclear reaction by mixing partial waves, predicts a correlation term in this reaction. A detailed study of the $sp$-mixing model is required to study the feasibility of a new type of time reversal symmetry violation search experiment. The correlation term ${\mathit{\sigma }}_n·\left({\mathit{k}}_n\times {\mathit{k}}_{\gamma }\right)$ in the ${}^{139}\mathrm{La}(\vec{n},\gamma )$ reaction has been studied by measuring $\gamma$-ray and neutron energies utilizing epithermal polarized neutrons and germanium detectors. The transverse asymmetry for single $\gamma$-ray transition was measured to be $0.60\pm 0.19$ in the $p$-wave resonance.

The spin structure of parity violating and time reversal invariance violating effects in neutron scattering is discussed. The explicit relations between these effects are presented in terms of functions nuclear spins and neutron partial widths of $p$-wave resonances.

A new time projection chamber (TPC) was developed for neutron lifetime measurement using a pulsed cold neutron spallation source at the Japan Proton Accelerator Research Complex (J-PARC). Managing considerable background events from natural sources and the beam radioactivity is a challenging aspect of this measurement. To overcome this problem, the developed TPC has unprecedented features such as the use of polyether-ether-ketone plates in the support structure and internal surfaces covered with $^6$Li-enriched tiles to absorb outlier neutrons. In this paper, the design and performance of the new TPC are reported in detail.Comment: 33 pages, 10 figure

Largely enhanced parity-violating effects observed in compound resonances induced by epithermal neutrons are currently attributed to the mixing of parity-unfavored partial amplitudes in the entrance channel of the compound states. Furthermore, it is proposed that the same mechanism that enhances the parity violation also enhances the breaking of time-reversal invariance in the compound nucleus. The entrance-channel mixing induces energy-dependent spin-angular correlations of individual $\gamma$ rays emitted from the compound nuclear state. For a detailed study of the mixing model, the $\gamma$-ray yield in the reaction of ${}^{117}\mathrm{Sn}(n,\gamma ){}^{118}\mathrm{Sn}$ was measured using a pulsed beam of polarized epithermal neutrons and Ge detectors. An angular dependence of asymmetric $\gamma$-ray yields for the orientation of the neutron polarization was observed.

This study entailed the successful deployment of a novel neutron interferometer that utilizes multilayer mirrors. The apparatus facilitates a precise evaluation of the wavelength dependence of interference fringes utilizing a pulsed neutron source. Our interferometer achieved an impressive precision of 0.02 rad within a 20-min recording time. Compared to systems using silicon crystals, the measurement sensitivity was maintained even when using a simplified disturbance suppressor. By segregating beam paths entirely, we achieved successful measurements of neutron-nuclear scattering lengths across various samples. The values measured for Si, Al, and Ti were in agreement with those found in the literature, while V showed a disparity of 45%. This discrepancy may be attributable to impurities encountered in previous investigations. The accuracy of measurements can be enhanced further by mitigating systematic uncertainties that are associated with neutron wavelength, sample impurity, and thickness. This novel neutron interferometer enables us to measure fundamental parameters, such as the neutron-nuclear scattering length of materials, with a precision that surpasses that of conventional interferometers.