Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number $A=42$, 46, 50, and 54 “$f$-shell” nuclei in (${}^3\mathrm{He}$, $t$) charge-exchange reactions. In the ${}^{42}\mathrm{Ca}\to {}^{42}\mathrm{Sc}$ reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As $A$ increases, a high-energy GT phonon excitation develops in the 6–11 MeV region. In the ${}^{54}\mathrm{Fe}\to {}^{54}\mathrm{Co}$ reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei.

The ${}^{150}\mathrm{Nd}$(${}^3\mathrm{He}$,$t$) reaction at $140$ MeV/u and ${}^{150}\mathrm{Sm}$($t$,${}^3\mathrm{He}$) reaction at $115$ MeV/u were measured, populating excited states in ${}^{150}\mathrm{Pm}$. The transitions studied populate intermediate states of importance for the (neutrinoless) $\beta \beta$ decay of ${}^{150}\mathrm{Nd}$ to ${}^{150}\mathrm{Sm}$. Monopole and dipole contributions to the measured excitation-energy spectra were extracted by using multipole decomposition analyses. The experimental results were compared with theoretical calculations obtained within the framework of the quasiparticle random-phase approximation, which is one of the main methods employed for estimating the half-life of the neutrinoless $\beta \beta$ decay ($0\nu \beta \beta$) of ${}^{150}\mathrm{Nd}$. The present results thus provide useful information on the neutrino responses for evaluating the $0\nu \beta \beta$ and $2\nu \beta \beta$ matrix elements. The $2\nu \beta \beta$ matrix element calculated from the Gamow-Teller transitions through the lowest $1^{+}$ state in the intermediate nucleus is maximally about half that deduced from the half-life measured in $2\nu \beta \beta$ direct counting experiments, and at least several transitions through $1^{+}$ intermediate states in ${}^{150}\mathrm{Pm}$ are required to explain the $2\nu \beta \beta$ half-life. Because Gamow-Teller transitions in the ${}^{150}\mathrm{Sm}$($t$,${}^3\mathrm{He}$) experiment are strongly Pauli blocked, the extraction of Gamow-Teller strengths was complicated by the excitation of the $2\hslash \omega$, $\Delta L=0$, $\Delta S=1$ isovector spin-flip giant monopole resonance (IVSGMR). However, the near absence of Gamow-Teller transition strength made it possible to cleanly identify this resonance, and the strength observed is consistent with the full exhaustion of the non-energy-weighted sum rule for the IVSGMR.

A neutron scintillation detector based on a position-sensitive photomultiplier has been developed for neutron spin echo and small angle neutron scattering measurements. This photomultiplier has good spatial resolution, less than 1 mm². The detection efficiency of gamma ray background is very low for using a thin ZnS/⁶LiF scintillator. The effective area of this detector is around 60 cm².

We describe an experimental search for deviations from the inverse-square law of gravity at the nanometer length scale using neutron scattering from noble gases on a pulsed slow neutron beam line. By measuring the neutron momentum transfer ($q$) dependence of the differential cross section for xenon and helium and comparing to their well-known analytical forms, we place an upper bound on the strength of a new interaction as a function of interaction length $\lambda$ which improves upon previous results in the region $\lambda <0.1\mathrm{nm}$, and remains competitive in the larger-$\lambda$ region. A pseudoexperimental simulation is developed for this experiment and its role in the data analysis is described. We conclude with plans for improving sensitivity in the larger-$\lambda$ region.