The SS-HORSE–NCSM method is generalized to the case of democratic decay into an odd number of fragments. This method is applied to the search for resonances in three-neutron system (trineutron) using ab initio no-core shell model calculations with realistic nucleon-nucleon ($NN$) potentials. The $3/2^{-}$ and $1/2^{-}$ strongly overlapping resonances are predicted when softened $NN$ interactions are used and are preferred over the case where bare $NN$ interactions of the chiral effective field theory are used with no resonance obtained.

Background: The microscopic description of $\alpha$ decay from the nucleons' degree of freedom involves a two-step process. The first consists of the clusterization of neutron and proton pairs; the second involves the tunneling process.

Purpose: A robust protocol for calculating the normalized spectroscopic factor (amount of clustering), as defined by Fliessbach, and its error is established and used for calculating the $\alpha$ width for the $0^{+}$ states of the nucleus ${}^{44}\mathrm{Ti}$.

Method: The Gamow shell model is used to calculate the structure part of the $\alpha$ decay (spectroscopic factor), while the Gamow wave function determines the reaction part (single-particle width).

Results: The spectroscopic factors and $\alpha$ width are calculated for the $0^{+}$ states of ${}^{44}\mathrm{Ti}$.

Conclusions: The normalization does not appreciably modify the ground-state clusterization, while the excited states do. The nonresonant continuum significantly increases the clustering of some of the excited states, particularly the $T=2$ state. The normalized formation amplitude looks like a single-particle wave function.

We have presented an enhanced relativistic density functional theory that comprehensively addresses proton resonance, emission processes, and proton-rich exotic nuclei. Our theory successfully resolves the long-range Coulomb potential issue by eliminating its singularity within the Dirac equation using the complex momentum representation. When applied to ${}^{120}\mathrm{Sn}$, our theory significantly improves alignment with advanced scattering data, surpassing the accuracy of traditional methods, even for exceptionally broad resonances. Additionally, our analysis of proton emissions from ${}^{37}\mathrm{Sc}$ and ${}^{39}\mathrm{Sc}$ accurately reproduces experimental $Q$ values and lifetimes. Our model exhibits superior agreement with time-dependent Dirac calculations compared to other methodologies, particularly in capturing nuances of narrow widths. Extending to proton-rich exotic nuclei, such as ${}^{26}\mathrm{P}$, we unveil detailed density distributions unconstrained by box size, revealing proton halo characteristics due to weakly bound $2s_{1/2}$ protons. This advancement in our relativistic density functional theory gives hope for reaching a more accurate and comprehensive understanding of nuclear phenomena across proton-rich systems.

We propose a theoretical method to calculate the stellar $\beta$-decay rates of nuclei in stellar environments with high temperature and density, based on the projected shell model, where contributions from both allowed and first-forbidden transitions are taken into account. As the first example, the stellar $\beta$-decay rate of one of the last $s$-process branching-point nuclei, ${}^{204}\mathrm{Tl}$, is calculated and studied, where all related transitions are first-forbidden transitions. For the terrestrial case, the ground-state–to–ground-state transition is a unique first-forbidden transition, which is described reasonably by our calculations. At the typical $s$-process temperature ($T\approx 0.3$ GK), nonunique first-forbidden transitions from thermally populated excited states of the parent nucleus are involved, and the effective rate from our calculations is much lower than the one from the widely used data tables by Takahashi and Yokoi. The effect of the quenching factors for nuclear matrix elements in first-forbidden transitions on the stellar $\beta$-decay rates is discussed as well.

We discuss two approaches which, by applying the screening method, permit one to include the long range proton-proton ($pp$) Coulomb force in proton-deuteron ($pd$) momentum-space scattering calculations. In the first one, based on the Alt-Grassberger-Sandhas (AGS) equation, presented in Phys. Rev. C 71, 054005 (2005) and Phys. Rev. C 72, 054004 (2005), one needs to renormalize elastic scattering amplitude before calculating observables. In the second treatment, proposed by us in Eur. Phys. J. A 41, 369 (2009), Eur. Phys. J. A 41, 385 (2009), and arXiv:2310.03433 [nucl.th], this renormalization is avoided. For the proton induced deuteron breakup reaction both approaches require renormalization of the corresponding transition amplitudes. We derive the basic equations underlying both methods under the assumption that all contributing partial wave states are included and explain why in our approach renormalization of the elastic scattering amplitude is superfluous. We show that in order to take into account in the screening limit all partial waves it is required that four additional terms, based on the three-dimensional and partial-wave projected $pp$ Coulomb $t$ matrices, identical for both approaches, must appear in transition amplitudes. We investigate the importance of these terms for elastic $pd$ scattering below the breakup threshold.

More and more halo nuclei or candidates have been identified or suggested in experiments in recent years. It was declared that the halo structure of ${}^{22}\mathrm{Al}$ is revealed by the large isospin asymmetry in ${}^{22}\mathrm{Si}/{}^{22}\mathrm{O}$ mirror Gamow-Teller transitions [Phys. Rev. Lett. 125, 192503 (2020)]. We highlight that a significant mirror asymmetry already exists between wave functions of the likely unbound nucleus ${}^{22}\mathrm{Si}$ and the doubly magic nucleus ${}^{22}\mathrm{O}$, which largely explains the observed asymmetry in the transitions. Furthermore, these transitions involve only the $1^{+}$ excited states of the daughter nuclei ${}^{22}\mathrm{Al}$ and ${}^{22}\mathrm{F}$. The $1^{+}$ state of ${}^{22}\mathrm{Al}$ cannot be considered a halo state due to its proton-unbound nature. An analysis of the spin parity suggests that a weakly bound $2s_{1/2}$ valence proton in the ground state of ${}^{22}\mathrm{Al}$ is improbable. To investigate the shell structure for the ground state of ${}^{22}\mathrm{Al}$, we employ the state-of-the-art deformed and triaxial relativistic Hartree-Bogoliubov theories in continuum. We find that a small $s$-wave component of $5\%$ appears for the weakly bound valence proton in ${}^{22}\mathrm{Al}$ only when triaxial deformation is considered. While the examination of densities and rms radii indicates that this small $s$-wave component is insufficient to form a discernible proton halo in ${}^{22}\mathrm{Al}$, slightly larger $2s_{1/2}$ occupations have been reported in other recent theoretical results. The question of how many low-$\ell$ components are sufficient to form a proton halo in the presence of the Coulomb barrier remains open. Thus, future measurements of reaction or interaction cross sections and momentum distributions of breakup fragments are highly desirable to verify whether ${}^{22}\mathrm{Al}$ is a halo nucleus.

We present a microscopic modeling for a decay of a heavy compound nucleus, starting from a nucleonic degree of freedom. To this end, we develop an approach based on a nonequilibrium Green's function, which is combined with a configuration-interaction approach based on a constrained density-functional theory. We apply this approach to a barrier-top fission of ${}^{236}\mathrm{U}$, restricting the model space to seniority zero configurations of neutrons and protons. We particularly focus on the distribution of the fission probability. We find that it approximately follows the ${\chi }^2$ distribution with the number of degrees of freedom $\nu$ of the order of 1, which is consistent with the experimental finding. We also show that $\nu$ corresponds to the number of those eigenstates of the many-body Hamiltonian which have significant components on both sides of a fission barrier and at the same time whose eigenenergy is close to the excitation energy of the system.

The smallness of the cross section of evaporation residues formed in the hot fusion reaction ${}^{48}\mathrm{Ca}+{}^{232}\mathrm{Th}$ is analyzed by the dinuclear system model (DNS). The capture probability has been calculated by solving the dynamical equations of motion for the relative distance between the centers of mass of the DNS nuclei. Fusion of nuclei is considered as evolution of the DNS to a stable compound nucleus. The fusion probability has a bell-like shape and quasifission is one of reasons causing smallness of the yield of the evaporation residues products. Another reason is the decrease of the fission barrier for the isotopes ${}^{275\text{–}285}\mathrm{Dm}$ related with the shell effects in the neutron structure. The agreement of the theoretical results obtained for the yield of the evaporation residues with the experimental data measured in the Factory of Superheavy Elements of Joint Institute for Nuclear Research is well.

Photoneutron reactions on ${}^{208}\mathrm{Pb}$ in the giant dipole resonance energy region have been investigated at the $\gamma$-ray beam line of the NewSUBARU facility in Japan. The measurements made use of quasimonochromatic laser Compton backscattering $\gamma$-ray beams in a broad energy range, from the neutron threshold up to 38 MeV, and of a flat-efficiency moderated ${}^3\mathrm{He}$ neutron detection system along with associated neutron-multiplicity sorting methods. We report absolute cross sections and mean photoneutron energies for the ${}^{208}\mathrm{Pb}(\gamma ,inX)$ reactions with $i=1$ to 4. The fine structure present in the ${}^{208}\mathrm{Pb}(\gamma ,n)$ cross sections at incident energies lower than 13 MeV has been observed. The photoabsorption cross section has been obtained as the sum of the $(\gamma ,inX)$ reaction cross sections. By reproducing the measured ring-ratio values at excitation energies below the two neutron separation energy, we were able to extract estimations on the ${}^{208}\mathrm{Pb}(\gamma ,n)$ photoneutron energy spectra and on the partial photoneutron cross sections for leaving the residual ${}^{207}\mathrm{Pb}$ in its ground and first two excited states. The present results are compared with data from the literature and statistical model calculations.

This present study explores the role of incomplete fusion in heavy-ion reactions alongside complete fusion, examining recoil ranges of populated residues. An attempt has been made to distinguish between complete and incomplete fusion contributions by analyzing linear momentum transfer from the projectile to the target nucleus. Employing the recoil-catcher activation technique, forward recoil range distributions for the ${}^{19}\mathrm{F}+{}^{169}\mathrm{Tm}$ system at energies around 96 and 106 MeV have been measured. Analysis of these recoil range distributions reveals characteristics of complete and incomplete fusion processes. Complete fusion reactions show larger recoil ranges, signifying comprehensive linear momentum transfer. On the other hand, residues exhibiting smaller recoil ranges result from partial linear momentum transfer due to incomplete fusion of the projectile. The forward recoil range distributions indicate an admixture of full and partial linear momentum transfer components in reactions with $\alpha$ particles in the exit channels. This behavior suggests projectile breakup caused by the Coulomb effect, offering valuable insights into fusion process dynamics.

We study the elliptic flow parameter and its event-by-event fluctuation in ${}^{197}\mathrm{Au}+{}^{197}\mathrm{Au}$ collisions at energies used in the STAR Beam Energy Scan (phase I) program, while using the string melting version of a multiphase transport (ampt) model as a baseline prediction. We employ different methods to determine the elliptic flow parameter, compare their values with each other, and study their dependencies on the collision centrality, transverse momentum, pseudorapidity, and nucleon-nucleon center of mass energy. Within the framework of the ampt model, we examine how the nonflow effects arising out of interparticle correlations influence the values of the elliptic flow parameter. We also study the centrality and energy dependencies of the event-by-event fluctuation of elliptic flow, and compare our simulation results with the STAR experimental data wherever they are available. We observe that the simulation can reasonably well reproduce the shape of the centrality dependence of the elliptic flow and its fluctuation as seen in the experiment. However, the simulation slightly underestimates the integrated values of the elliptic flow parameter, and it does not quite match with the transverse momentum and pseudorapidity dependencies observed in the experiment. We also observe that the contribution of nonflow effects to the centrality dependence of elliptic flow and its fluctuation is marginal. Fluctuations in the elliptic flow depend nonmonotonically on the collision energy involved, in the experiment as well as in the simulation.

Using six different parametrizations of the quantum hadrodynamics (one of which is original), I study how different values of the symmetry energy slope $L$ affect some microscopic and macroscopic properties of neutron stars, such as the proton fraction, the maximum mass, the radius of the canonical $1.4M_{\odot }$ star and its dimensionless tidal parameter $\mathrm{\Lambda }$. I show that while most quantities present the same qualitative results, the tidal parameter can increase or decrease with the slope, depending on the model. Moreover, special attention is given to the minimum mass that enables the direct URCA process to occur in neutron stars' interiors ($M_{\mathrm{DU}})$. Assuming the weak constraint $M_{\mathrm{DU}}>1.35M_{\odot }$, one can see that the maximum value of $L$ that satisfies it lies between 79 and 86 MeV, a range of only 7 MeV. Therefore, $M_{\mathrm{DU}}$ is an easy way to impose upper bounds to the slope.

Our knowledge about neutron star (NS) masses is renewed once again due to the recognition of the heaviest NS PSR $\mathrm{J}0952-0607$. By taking advantage of both mass observations of supermassive neutron stars and the tidal deformability derived from event GW170817, a joint constraint on tidal deformability is obtained. A wide-ranging correlation between NS pressure and tidal deformability within the density range from saturation density ${\rho }_0$ to $5.6{\rho }_0$ is discovered, which directly yields a constrained NS equation of state (EoS). The newly constrained EoS has a small uncertainty and a softer behavior at high densities without the inclusion of extra degrees of freedom, which shows its potential to be used as an indicator for the component of the NS core.

The persistence of $\alpha$-cluster states in light nuclei has aroused great interest in nuclear physics during the past several decades, and the cluster-core configuration is expected to play a key role in interpreting the spectroscopic properties of heavier nuclei. In this study, we have systematically investigated the energy spectra of $\alpha$-cluster structures above the double shell closures within the binary cluster-core model (BCM), especially for rotational bands with negative parities. The reliability and integrity of BCM can be proved by the excellent reproduction of energy spectra. Analogously, this kind of picture is generalized to the case of heavier clusters above doubly magic core ${}^{208}\mathrm{Pb}$ by modifying the quantum condition for the number of nodes in the cluster-core wave function. The uncertainties of relevant parameters in the nuclear potential are determined by the nonparametric resampling strategy, leading to our statistical results on these states with negative parities. It is hoped that our present study can stimulate further insight into clustering phenomena of heavy and superheavy nuclei.

A series of fusion evaporation reactions induced by the ${}^{54}\mathrm{Cr}^{17+}$ beam have been performed using the gas-filled recoil separator SHANS2. The excitation functions of ${}^{54}\mathrm{Cr}+{}^{159}\mathrm{Tb}$ and ${}^{54}\mathrm{Cr}+{}^{165}\mathrm{Ho}$ reactions were measured. The systematics of cross sections for reactions with ${}^{40}\mathrm{Ar}, {}^{48}\mathrm{Ca}, {}^{50}\mathrm{Ti}$, and ${}^{54}\mathrm{Cr}$ projectiles are compiled and discussed. It is suggested that employing the ${}^{54}\mathrm{Cr}$ beam holds the potential for synthesizing neutron-deficient actinide nuclei. In addition, we attempted to synthesize undiscovered americium isotopes with ${}^{175}\mathrm{Lu}({}^{54}\mathrm{Cr},3n–4n){}^{225,226}\mathrm{Am}$ reactions. No events were observed originating from ${}^{225}\mathrm{Am}$ and ${}^{226}\mathrm{Am}$, and the upper limits were estimated to be 2.1 and 1.7 pb, respectively. The significantly low fission barrier of the com- pound nucleus ${}^{229}\mathrm{Am}$, which leads to the small survival probability, might be a possible reason for the low cross sections.

We analyze particle number fluctuations in the crossover region near the critical endpoint of a first-order phase transition by utilizing molecular dynamics simulations of the classical Lennard-Jones fluid. We extend our previous study [V. A. Kuznietsov et al., Phys. Rev. C 105, 044903 (2022)] by incorporating longitudinal collective flow. The scaled variance of particle number distribution inside different coordinate and momentum space acceptances is computed through ensemble averaging and found to agree with earlier results obtained using time averaging, validating the ergodic hypothesis for fluctuation observables. Presence of a sizable collective flow is found to be essential for observing large fluctuations from the critical point in momentum space acceptances. We discuss our findings in the context of heavy-ion collisions.

We extend the investigation of jet transport coefficients within the effective dynamical quasiparticle model (DQPM)—constructed to describe nonperturbative QCD phenomena of the strongly interacting quark-gluon plasma (sQGP) in line with the lattice QCD equation of state—by accounting for inelastic $2\to 3$ reactions with gluon radiation in addition to the elastic scattering of partons. The elastic and inelastic reactions are calculated explicitly within leading-order Feynman diagrams with effective propagators and vertices from the DQPM by accounting for all channels and their interferences. We present the results for the jet transport coefficients such as the transverse momentum transfer squared $\widehat{q}$ per unit length as well as the energy loss $dE/dx$ per unit length in the sQGP and investigate their dependence on the temperature $T$ and momentum of the jet parton depending on the choice of the strong coupling constant ${\alpha }_s$ in thermal, jet parton, and radiative vertices. For the latter, we consider different scenarios used in the literature and find a very strong dependence of $\widehat{q}$ and $dE/dx$ on the choice of ${\alpha }_s$. Moreover, we explore the relation of $\widehat{q}/T^3$ to the ratio of specific shear viscosity to entropy density $\eta /s$ and show that the ratio $T^3/\widehat{q}$ to $\eta /s$ has a strong $T$ dependence—especially when approaching $T_c$—on the choice of ${\alpha }_s$ in scattering vertices.