EDITORS' SUGGESTION
At low temperatures (10–1000 K), negative muons injected into a mixture of deuterium (D) and tritium (T) can catalyze the fusion reaction into helium, which yields a neutron and 17.6 MeV energy. Following the catalyzed reaction, free muons can facilitate another fusion reaction, leading to a cyclic reaction known as muon-catalyzed fusion (CF), a potential candidate for energy production. CF has recently regained considerable research interest owing to several new developments and applications. For the nuclear reaction processes, the authors provide an elegant alternative to more complicated coupled-channels (CC) models (Kamimura , PRC 107, 034607) by replacing in the transition matrix the exact three-body wave function with a solution that uses a tailored - optical potential. The calculated results reproduce well those of the full CC calculations, and the proposed tractable transition-matrix model promises applications to other CF systems. The predicted low-energy negative muon spectrum will also be useful for the generation of an ultraslow negative muon beam by utilizing the CF for various applications, such as a scanning negative muon microscope and an injection source for the muon collider.
Qian Wu and Masayasu Kamimura
Phys. Rev. C 109, 054625 (2024)
EDITORS' SUGGESTION
Several past experiments such as SAGE, GALLEX, and BEST reported lower than expected neutrino capture rates on Ga. The origin of this so-called “gallium anomaly” could potentially indicate new neutrino physics, unless there was a more mundane explanation. Because the measured half-life of the electron-capture decay of Ge can be used to calculate the neutrino-capture cross section on Ga, the authors carried out three separate measurements to determine the half-life of Ge with high precision. Their new result of days for the Ge half-life is consistent with the currently accepted value, but significantly more precise. It rules out an unexpectedly long Ge half-life as a potential explanation of the puzzling anomaly, leaving the anomaly’s origin an open question.
E. B. Norman et al.
Phys. Rev. C 109, 055501 (2024)
EDITORS' SUGGESTION
The modeling of relativistic collisions of nuclei is typically performed by numerically solving the equations of relativistic hydrodynamics. In a few rare cases, exact solutions to these equations exist. The authors derive two novel exact solutions which practitioners may use to verify their hydrodynamics algorithms. The work highlights the importance of an accurate description of the freeze-out configuration in systems characterized by large transverse and longitudinal flows and in collisions with large flow gradients, particularly in small systems.
Owen Bradley and Christopher Plumberg
Phys. Rev. C 109, 054913 (2024)
EDITORS' SUGGESTION
This work reports the first experimental measurements made at a magnetic confinement fusion device (JET) of the reaction, indicating the presence of an intermediate He state in the two-body resonant reaction . Such measurements, in which two tritium nuclei (H or T) fuse into helium (He or ), are relevant for modeling the neutron emission spectrum and estimating fuel content and confinement characteristics for magnetic confinement fusion. The results are also relevant for solar physics, as the mirror reaction plays a role in the proton-proton chain of solar fusion.
B. Eriksson et al.
Phys. Rev. C 109, 054620 (2024)
EDITORS' SUGGESTION
The transition from the nucleon to the resonance is a sensitive test for models of the nucleon structure. A magnetic dipole () quark spin-flip transition essentially dominates photoexcitation of the , but smaller components in the nucleon and wave functions allow also electric quadrupole () contributions. The ratio then provides fundamental information on both the spatial deformation of the nucleon or , and on the corresponding states in their quark-model wave functions. The authors measured the ratio via single production from the proton with a circularly polarized photon beam and a longitudinally polarized proton target, exploiting the presence of interference terms between the measured amplitudes that enhance the effect of smaller contributions. This most precise experimental result to date for the ratio gives deep insight into the nucleon properties and provides a precision benchmark for all nonperturbative QCD models.
E. Mornacchi et al. (A2 Collaboration at MAMI)
Phys. Rev. C 109, 055201 (2024)
EDITORS' SUGGESTION
Efforts toward a precise determination of and low-energy tests of the electroweak Standard Model have been ongoing for many years. The authors report a comprehensive re-evaluation of the values in superallowed nuclear decays based on a fully data-driven analysis of the nuclear -decay form factor. They utilize isospin relations to connect the nuclear charged weak distribution to the measurable charge distributions. The approach supersedes previous shell-model estimations and allows for a rigorous quantification of theory uncertainties in the phase-space factor, using experimental input rather than nuclear models. The work identifies the need for specific future experimental research to drive further understanding toward a regime of precision that is relevant for weak-interaction physics and thus for physics beyond the Standard Model.
Chien-Yeah Seng and Mikhail Gorchtein
Phys. Rev. C 109, 045501 (2024)
EDITORS' SUGGESTION
Neutron transmission experiments can realize a high-sensitivity search for time-reversal invariance violation (TRIV) in nucleon-nucleon interactions through the same enhancement mechanism observed for large parity violating (PV) effects in neutron-induced compound nuclear processes. A recent polarized beam/polarized target measurement has now quantified the sensitivity for the best-known case, the 0.75 eV -wave resonance in La. By determining the spin-dependent nuclear structure factor that relates TRIV and PV cross sections, this work shows that a future search for -odd/-odd interactions in forward transmission of polarized neutrons on polarized La would possess high TRIV sensitivity.
R. Nakabe et al.
Phys. Rev. C 109, L041602 (2024)
EDITORS' SUGGESTION
Neutrino experiments such as long-baseline oscillation measurements can determine properties of fundamental particles, but the present systematic uncertainties, e.g., in the neutrino-nucleus cross sections, must be significantly reduced. The authors determine the O spectral function from an - calculation with realistic two- and three-body interactions that is benchmarked against earlier He results. They then obtain good results in the relativistic regime for quasi-elastic electron scattering as well as for neutrino scattering data from T2K. The predictions for both electron and neutrino scattering identify a particular need for low-energy electron-scattering data on O, for which a program is underway at MAMI in Germany. And being able to propagate the theoretical uncertainties to the final cross sections promises improved understanding of the anticipated more precise results from next-generation neutrino experiments.
J. E. Sobczyk and S. Bacca
Phys. Rev. C 109, 044314 (2024)