EDITORS' SUGGESTION
The astrophysical origin for the chemical elements between the first and second -process peaks is a matter of intense debate, with a number of nucleosynthesis processes at explosive stellar environments possibly contributing to their production. Modeling neutron-capture processes that would produce these elements requires reliable data on the trends of neutron separation energies of neutron-rich isotopes which are highly unstable and not readily accessible by experiment. This work describes the first application of an experimental technique, time-of-flight-magnetic-rigidity (ToF-B), that is well-suited to measure masses of nuclei with very short half-lives in beams with relatively low intensities. The two-neutron separation energy deduced from the measured masses exhibits a smooth trend consistent with theoretical predictions within the range of experimental uncertainty, indicating that there is no sudden shape transition in these isotopes as hinted at by previous data. The successful application of the ToF-B technique to isotopes with at the NSCL S800 spectrograph gives hope for a comprehensive program of mass measurements for isotopes relevant to -process models with the same device at FRIB.
K.-L. Wang et al.
Phys. Rev. C 109, 035806 (2024)
EDITORS' SUGGESTION
Neutrino mass is a key parameter in nuclear and particle physics and in cosmology. The Project 8 Collaboration developed an innovative method with potential to improve the current mass limits by more than an order of magnitude. Announced in a paper published last September (PRL 131, 102502; see also the Synopsis at https://physics.aps.org/articles/v16/s121), the method measures the frequency of radiation from tritium -decay electrons spiraling in a magnetic field. In the current paper the authors provide the details of this unique measurement technique including the hardware and the role of simulations and precision spectroscopy that enabled their new direct mass measurement. This first, small-volume demonstration, along with the precision reached, shows a clear path to improve in future experiments on the conservative upper limit for the neutrino mass obtained here.
A. Ashtari Esfahani et al. (Project 8 Collaboration)
Phys. Rev. C 109, 035503 (2024)
EDITORS' SUGGESTION
Optical potentials, either phenomenological or microscopic, are used in nuclear reactions to reduce the complexity of the quantum many-body scattering to a tractable one-body problem. In this work the authors extend to heavier nuclei a highly predictive microscopic approach based on - self-consistent Green’s function (SCGF) calculations that use and chiral interactions as the only input. The computed elastic proton scattering off Ca and Ni isotope chains demonstrate the stability of the SCGF input, a method that requires only polynomial scaling of computational resources and reaches masses up to 140 nucleons or more. The predictive power of their optical potential promises interesting implications for studying nuclei away from stability, a frontier in nuclear science including nuclear astrophysics in the coming years.
M. Vorabbi et al.
Phys. Rev. C 109, 034613 (2024)
EDITORS' SUGGESTION
Far away from the heaviest known nuclei, an island of relatively stable nuclei should exist in the nuclear chart. Reaching that island of stability requires a nuclear reaction that will transfer a large number of nucleons from one nucleus to another, such as in the collision of two actinide nuclei, which are heavy and already neutron-rich. In one particular collision scenario, ternary quasifission, the composite system formed by the two colliding nuclei is not in equilibrium, splitting into three fragments, instead of the more commonly observed binary fission process. The authors report a systematic study of ternary quasifission in U + U collisions in a microscopic framework that has been successfully applied to various nuclear phenomena. They find that including octupole deformation has a pronounced effect on the formation of the middle fragment. For tail-to-tail and tail-to-side collisions, the model calculations predict the formation of very heavy neutron-rich systems in certain energy intervals, a result that is potentially interesting for the synthesis of superheavy elements.
D. D. Zhang et al.
Phys. Rev. C 109, 024316 (2024)
EDITORS' SUGGESTION
In 1954 Fred Hoyle postulated that a 7.65 MeV excited state in C had to exist for carbon-based life to develop on Earth. During stellar helium burning, such a state allows a short-lived Be, formed from two particles, to resonantly react with a third particle to form this state which can decay to the C ground state via or electron-positron pair emission. The branching fraction for this radiative decay determines the amount of C produced in stars. A recent experiment suggested that the decay was significantly different from previous results from the 1960’s and 1970’s, adding considerable uncertainty to this important reaction. This paper uses modern detection technology to remeasure the branching ratio with reduced uncertainties compared with the new result and confirms that the earlier results were correct, thus significantly reducing the uncertainty in stellar C production.
Zifeng Luo (罗梓锋) et al.
Phys. Rev. C 109, 025801 (2024)
EDITORS' SUGGESTION
This work reports on an emulator for the evaluation of many-body observables based on an eigenvector continuation (EC) framework as an example of a reduced-basis method for a detailed study of the exactly solvable pairing Hamiltonian that serves as a model for nuclear superfluidity. EC is established as a robust resummation tool for many-body perturbation theory even though the bare perturbative expansion breaks down. The authors obtain a reliable, computation-saving, description of the exact solution with a small number of training points, provided these are taken from both sides of the pairing phase transition.
M. Companys Franzke, A. Tichai, K. Hebeler, and A. Schwenk
Phys. Rev. C 109, 024311 (2024)