How accurately can we predict synthesis cross sections of superheavy elements？

Synthesis of superheavy elements beyond oganesson is facing new challenges as new target–projectile combinations are necessary. Guidance from models is thus expected for future experiments. However, hindered fusion models are not well established and predictions in the fission barriers span few MeVs. Consequently, predictions are not reliable. Strategies to constrain both fusion hindrance and fission barriers are necessary to improve the predictive power of the models. But, there is no hope to get an accuracy better than one order of magnitude in fusion–evaporation reactions leading to superheavy elements synthesis.

An investigation of ab initio shell-model interactions derived by no-core shell model

The microscopic shell-model effective interactions are mainly based on the many-body perturbation theory(MBPT), the first work of which can be traced to Brown and Kuo's first attempt in 1966, derived from the Hamada-Johnston nucleon-nucleon potential.However, the convergence of the MBPT is still unclear. On the other hand, ab initio theories, such as Green's function Monte Carlo(GFMC), no-core shell model(NCSM), and coupled-cluster theory with single and double excitations(CCSD), have made many progress in recent years. However, due to the increasing demanding of computing resources, these ab initio applications are usually limited to nuclei with mass up to A = 16. Recently, people have realized the ab initio construction of valence-space effective interactions, which is obtained through a second-time renormalization, or to be more exactly, projecting the full-manybody Hamiltonian into core, one-body, and two-body cluster parts. In this paper, we present the investigation of such ab initio shell-model interactions, by the recent derived sd-shell effective interactions based on effective J-matrix Inverse Scattering Potential(JISP) and chiral effective-field theory(EFT) through NCSM. In this work, we have seen the similarity between the ab initio shellmodel interactions and the interactions obtained by MBPT or by empirical fitting. Without the inclusion of three-body(3-bd) force,the ab initio shell-model interactions still share similar defects with the microscopic interactions by MBPT, i.e., T = 1 channel is more attractive while T = 0 channel is more repulsive than empirical interactions. The progress to include more many-body correlations and 3-bd force is still badly needed, to see whether such efforts of ab initio shell-model interactions can reach similar precision as the interactions fitted to experimental data.

Influence of coalescence parameters on the production of protons and Helium-3 fragments

The time evolution of protons and 3He fragments from Au+Au/Pb+Pb reactions at 0.25, 2, and 20 Ge V/nucleon is investigated with the potential version of the Ultrarelativistic Quantum Molecular Dynamics（Ur QMD） model combined with the traditional coalescence afterburner. In the coalescence process, the relative distance R0 and relative momentum P0 are surveyed in the range of 3-4 fm and 0.25-0.35 Ge V/c, respectively. For both clusters, a strong reversed correlation between R0 and P0is seen and it is time-dependent as well. For protons, the accepted（R0, P0） bands lie in the time interval 30-60 fm/c, while for 3He, a longer time evolution（at about 60-90 fm/c） is needed. Otherwise, much smaller R0 and P0values should be chosen. If we further look at the rapidity distributions from both central and semi-central collisions, it is found that the accepted [tcut,（R0, P0）] assemble can provide consistent results for proton yield and collective flows especially at mid-rapdities, while for 3He, the consistency is destroyed at both middle and projectile-target rapidities.

α-decay study of ^(218)Ac and ^(221)Th in ^(40)Ar+^(186)W reaction

In this study,^(218)Ac and ^(221)Th nuclides were produced via the heavy-ion induced fusion evaporation reaction ^(40)Ar+^(186)W.Their decay properties were studied with the help of the gas-filled recoil spectrometer SHANS and a digital data acquisition system.The cross section ratio between ^(222)Pa and ^(218)Ac was extracted experimentally,withmeasured value 0.69(9).Two new possible α decay branches to ^(221)Th are suggested.The valence neutron configurations for the daughter ^(217)Ra are discussed in terms of the hindrance factors.