EDITORS' SUGGESTION
The treatment of particle correlations and the description of clusters in the nuclear medium are important aspects that need to be better understood in the theoretical description of nuclear matter and the simulation of heavy-ion collisions. The authors propose a novel treatment of clustering for transport calculations based on a mechanism that suppresses cluster formation due to the Pauli principle via a medium-dependent cutoff in the momentum distribution of the clusters. The impact of clusters on the dynamics of unstable nuclear matter is clearly seen, and a `distillation’ mechanism is observed that affects the distribution of clusters between the low- and high-density regions. Although the approach has room for improvements, it captures the essential physics, and promises to have an impact on the further development of the field.
Rui Wang, Stefano Burrello, Maria Colonna, and Francesco Matera
Phys. Rev. C 110, L031601 (2024)
EDITORS' SUGGESTION
The nature of dark matter is one of the outstanding problems in particle physics and cosmology. To assist in the search for dark matter (DM), the authors examine the most general interactions between weakly interacting massive particles (WIMPs), assumed to be spin-1/2 fermions, and isotopes of the lightest nuclei, hydrogen and helium, using chiral effective field theory for a wide range of masses and coupling constants. The authors conclude that the scalar nuclear response functions are much greater than the others and severely constrained by the existing limits provided by experiments. The present study could be extended to other possible types of DM interactions, lighter DM candidates or heavier nuclei, such as lithium, argon, and xenon, currently widely used in dark matter detectors.
Elena Filandri and Michele Viviani
Phys. Rev. C 110, 034002 (2024)
EDITORS' SUGGESTION
The proton dripline demarcates the nuclear landscape on the neutron-deficient side. A measurement at the SIS/FRS facility at GSI in Darmstadt, Germany of the anatomy of the immediate breakup of fragile Al into Mg + proton has now established that Al is unbound against proton emission in its ground state. The result thus places Al as the first Al isotope beyond the proton dripline. Its precise, negative proton separation energy will be a benchmark for nuclear structure models that treat nuclei as open quantum systems.
D. Kostyleva et al.
Phys. Rev. C 110, L031301 (2024)
EDITORS' SUGGESTION
Lattice QCD calculations at finite temperature and zero or small baryon chemical potential have shown that there is no phase transition separating quasi-free quarks and those confined in baryons. Quarkyonic matter is a hypothetical state where quarks and baryons can coexist in a single Fermi sphere; quarks occupy the low momenta levels, hadrons the high momenta ones. This paper puts forward the idea that normal nuclear matter may, in fact, be quarkyonic and that the existence of this exotic phase may already have been seen in current electron-nucleus scattering data.
Volker Koch, Larry McLerran, Gerald A. Miller, and Volodymyr Vovchenko
Phys. Rev. C 110, 025201 (2024)
EDITORS' SUGGESTION
- calculations of atomic nuclei have revolutionized nuclear structure physics. Yet challenges remain, not least the reliable calculation of nuclear radii. In a concurrent development, modern machine-learning algorithms have excelled in a variety of computational tasks such as pattern recognition and interpolation. The authors have applied artificial neural networks (ANNs) to the extrapolation of no-core shell model calculations to infinite model spaces, effectively circumventing their computational limitations. In particular, the results show that min-max normalization, a common technique in machine learning, leads to the best results for radii. These advances offer hope that the ANN architecture is capable of handling other observables such as electromagnetic moments and transition strengths.
Tobias Wolfgruber, Marco Knöll, and Robert Roth
Phys. Rev. C 110, 014327 (2024)
EDITORS' SUGGESTION
Atomic nuclei near mass 80 with approximately equal numbers of protons and neutrons are known to be strongly deformed while different shapes coexist in the same nucleus. These phenomena have challenged nuclear models but are also an opportunity to test the advances in theoretical approaches. The authors perform - coupled-cluster calculations for even-even nuclei near neutron-deficient Zr, including calculations of transitions, using chiral and forces. The results adequately describe shape coexistence even if they cannot unambiguously determine ground-state shapes. The calculations are a significant step forward in mass number for - computations of deformed nuclei.
B. S. Hu, Z. H. Sun, G. Hagen, and T. Papenbrock
Phys. Rev. C 110, L011302 (2024)
EDITORS' SUGGESTION
Recent observations by the ATOMKI Collaboration of anomalies in electron-positron pair production following proton capture on light nuclides has led to the postulation of a new boson with mass around 17 MeV. Here a team of scientists from the United States, Canada, and France presents the most detailed microscopic calculations to date of the proton capture reactions, and is unable to find a conventional explanation for the anomalies. While these calculations do not confirm the existence of the so-called X17 boson, they provide strong motivation for continued and independent experiments to investigate the ATOMKI results. Further refinements of the calculations may provide theoretical constraints for future data.
P. Gysbers et al.
Phys. Rev. C 110, 015503 (2024)
EDITORS' SUGGESTION
Nucleosynthesis during the Big Bang (BBN) can produce the lightest elements, including lithium, but the observed abundance of lithium in old stellar populations is much less than that predicted from BBN. To solve this so-called “lithium puzzle”, it had been postulated that a previously unobserved resonance in Be could deplete lithium through resonant proton capture on Li and thus account for the deficit. The authors performed a detailed study using information from all possible reactions that could be influenced by such a state, utilizing the stringent constraint imposed by the unitarity of the scattering matrix. They conclude that the postulated state in Be is highly unlikely, but they also suggest that additional radiative capture data are required to solve lingering discrepancies.
P. M. Prajapati and R. J. deBoer
Phys. Rev. C 110, 015802 (2024)