We present a new framework to treat the dissipation and fluctuation dynamics associated with nucleon-nucleon scattering in heavy-ion collisions. The two-body collision processes are effectively described in terms of the diffusion of nucleons in viscous nuclear media, governed by a set of Langevin equations in momentum space. The new framework combined with the usual mean-field dynamics can be used to simulate heavy-ion collisions at intermediate energies. As a proof of principle, we simulate Au + Au reactions and obtain results consistent with other existing codes under the same constrained conditions. We also study the formation of fragments in Sn + Sn reactions at 50 MeV/nucleon, and results are discussed and compared to two other models commonly employed for collisions.

Background: Previous studies of $(d,p)$ reactions in three-body (proton, neutron, nuclear core) systems revealed a nontrivial effect of the core excitation: the transfer cross section cannot be factorized into the spectroscopic factor and the single-particle cross section obtained neglecting the core excitation. This observable, up to a kinematic factor, is the angular distribution of the core nucleus in the $(p,d)$ reaction.

Purpose: The study of the core excitation effect for the most closely related observable in the $(p,pn)$ three-body breakup, i.e., the core angular distribution, is the aim in the present work.

Methods: Breakup of the one-neutron halo nucleus in the collision with the proton is described using three-body Faddeev-type equations extended to include the excitation of the nuclear core. The integral equations for transition operators are solved in the momentum-space partial-wave representation.

Results: Breakup of ${}^{11}\mathrm{Be}$ nucleus as well as of model $A=11p$-wave nuclei is studied at beam energies of 30, 60, and 200 MeV per nucleon. Angular and momentum distributions for the ${}^{10}\mathrm{Be}$ core in ground and excited states is calculated. In sharp contrast to $(p,d)$ reactions, the differential cross section in most cases factorizes quite well into the spectroscopic factor and the single-particle cross section.

Conclusions: Due to different reaction mechanisms the core excitation effect in the breakup is very different from transfer reactions. A commonly accepted approach to evaluate the cross section, i.e., the rescaling of single-particle model results by the corresponding spectroscopic factor, appears to be reliable for breakup though it fails in general for transfer reactions.

In the study of the odd-$Z$, even-$N$ nuclei ${}^{243}\mathrm{Es}$ and ${}^{249}\mathrm{Md}$, performed at the University of Jyväskylä, the fusion-evaporation reactions ${}^{197}\mathrm{Au}({}^{48}\mathrm{Ca},2n){}^{243}\mathrm{Es}$ and ${}^{203}\mathrm{Tl}({}^{48}\mathrm{Ca},2n){}^{249}\mathrm{Md}$ have been used for the first time. Fusion-evaporation residues were selected and detected using a gas-filled separator coupled with its focal-plane spectrometer. For ${}^{243}\mathrm{Es}$, the recoil decay correlation analysis yielded a half-life of $24\pm 3\mathrm{s}$ and a maximum production cross section of $37\pm 10\mathrm{nb}$. In the same way, a half-life of $26\pm 1\mathrm{s}$, an $\alpha$-branching ratio of $75\pm 5\%$, and a maximum production cross section of $300\pm 80\mathrm{nb}$ were determined for ${}^{249}\mathrm{Md}$. The decay properties of ${}^{245}\mathrm{Es}$, the daughter of ${}^{249}\mathrm{Md}$, were also measured: an $\alpha$-branching ratio of $54\pm 7\%$ and a half-life of $65\pm 6\mathrm{s}$. Experimental cross sections were compared to the results of calculations performed using the kewpie2 statistical fusion-evaporation code.

The use of the inverse kinematics technique and a magnetic spectrometer permits the simultaneous measurement of proton and neutron content of full fission fragment distributions. This paper reports new measurements of five fissioning systems—${}^{238}\mathrm{U},{}^{239}\mathrm{Np},{}^{240}\mathrm{Pu},{}^{244}\mathrm{Cm}$, and ${}^{250}\mathrm{Cf}$—produced in inelastic scattering, transfer, and fusion reactions at different excitation energies. As a result, isotopic, elemental, and isotonic fission yields are presented. The contribution of the different fission modes and the proton even-odd effect are studied. Structure effects are investigated by means of the neutron excess and the total neutron multiplicity as a function of the fragment atomic number.

We propose the quark mean-field bag (QMFB) model by incorporating the bag confinement mechanism in the original quark mean-field model. Nuclear matter and neutron star properties are studied with the QMFB model. For the study of the bag effect, we fit 12 parameter sets by reproducing the empirical saturation properties of nuclear matter. Quark confinement is found to be mainly demonstrated by the bag after it is included in the model, instead of the confining potential. For nuclear matter, the bag decreases the binding energy and increases the symmetry energy. For neutron stars, the bag affects significantly the radius $R$ of a $1.4M_{\odot }$ star, with the maximum mass only slightly modified. The bag also has a large suppression effect on the well-accepted $R$ versus $L$ dependence, with $L$ the symmetry energy slope at the saturation density.

Coulomb shifts of the linear-chain states are theoretically investigated for the mirror pair of ${}^{14}\mathrm{C}$ and ${}^{14}\mathrm{O}$ by using the antisymmetrized molecular dynamics. Energy shift of the $\sigma$-bond linear-chain states is found and it is due to the reduction in the Coulomb energy associated with the spatially extended $\sigma$ orbit. This new signature supports the existence of the linear-chain formation and encourages further experimental investigations.

We report on the first femtoscopic measurement of baryon pairs, such as $p-p, p-\mathrm{\Lambda }$, and $\mathrm{\Lambda }-\mathrm{\Lambda }$, measured by ALICE at the Large Hadron Collider (LHC) in proton-proton collisions at $\sqrt{s}=7\mathrm{TeV}$. This study demonstrates the feasibility of such measurements in $pp$ collisions at ultrarelativistic energies. The femtoscopy method is employed to constrain the hyperon-nucleon and hyperon-hyperon interactions, which are still rather poorly understood. A new method to evaluate the influence of residual correlations induced by the decays of resonances and experimental impurities is hereby presented. The $p-p, p-\mathrm{\Lambda }$, and $\mathrm{\Lambda }-\mathrm{\Lambda }$ correlation functions were fitted simultaneously with the help of a new tool developed specifically for the femtoscopy analysis in small colliding systems: Correlation Analysis Tool using the Schrödinger equation (CATS). Within the assumption that in $pp$ collisions the three particle pairs originate from a common source, its radius is found to be equal to $r_0=1.125\pm 0.018\left(\mathrm{stat}\right){}_{-0.035}^{+0.058}\left(\mathrm{syst}\right)$ fm. The sensitivity of the measured $p-\mathrm{\Lambda }$ correlation is tested against different scattering parameters, which are defined by the interaction among the two particles, but the statistics is not sufficient yet to discriminate among different models. The measurement of the $\mathrm{\Lambda }-\mathrm{\Lambda }$ correlation function constrains the phase space spanned by the effective range and scattering length of the strong interaction. Discrepancies between the measured scattering parameters and the resulting correlation functions at LHC and RHIC energies are discussed in the context of various models.

We perform self-consistent Skyrme Hartree-Fock calculations with the Coulomb exchange functional using the generalized gradient approximation (GGA). It is found that the Perdew-Burke-Ernzerhof GGA (PBE-GGA) Coulomb exchange functional is able to reproduce the exact-Fock energy for nuclei in a wide region of the nuclear chart with one adjustable parameter. The remaining error of the GGA Coulomb exchange energy with respect to the exact-Fock energy dominantly comes from the functional-driven error.

A set of prompt partial $\gamma$-ray production cross sections from thermal neutron capture were measured for the ${}^{139}\mathrm{La}(n,\gamma )$ reaction using a guided beam of subthermal (thermal and cold) neutrons incident on a ${}^{\mathrm{nat}}\mathrm{La}_2{\mathrm{O}}_3$ target at the Prompt Gamma Activation Analysis facility of the Budapest Research Reactor. Absolute ${}^{140}\mathrm{La}$ cross sections were determined relative to the well-known comparator ${}^{35}\mathrm{Cl}(n,\gamma )$ cross sections from the irradiation of a stoichiometric ${}^{\mathrm{nat}}\mathrm{LaCl}_3$ sample. The total cross section for radiative thermal neutron capture on ${}^{139}\mathrm{La}$ from the sum of experimentally measured cross sections observed to directly feed the ${}^{140}\mathrm{La}$ ground state was determined to be ${\sigma }_0^{\mathrm{expt}}=8.58\left(50\right)$ b. To assess completeness of the decay scheme and as a consistency check, the measured cross sections for transitions feeding the ground state from levels below a critical energy of $E_c=285$ keV were combined with a modeled contribution accounting for ground-state feeding from the quasicontinuum to arrive at a total cross section of ${\sigma }_0=9.36\left(74\right)$ b. In addition, a neutron-separation energy of $S_n=5161.001\left(21\right)$ keV was determined from a least-squares fit of the measured primary $\gamma$-ray energies to the low-lying levels of the ${}^{140}\mathrm{La}$ decay scheme. Furthermore, several nuclear structure improvements are proposed for the decay scheme. The measured cross-section and separation-energy results are comparable to earlier measurements of these quantities.

Background: Despite remarkable success of the statistical model (SM) in describing decay of excited compound nuclei (CN), reproduction of the observables from heavy ion-induced fusion-fission reactions is often quite challenging. Ambiguities in choosing the input parameters, lack of clarity about inclusion of various physical effects in the model, and contradictory requirements of input parameters while describing different observables from similar reactions are among the major difficulties of modeling decay of fissile CN.

Purpose: This work attempts to overcome the existing inconsistencies by inclusion of important physical effects in the model and through a systematic analysis of a large set of data over a wide range of CN mass ($A_{\mathrm{CN}}$).

Method: The model includes the shell effect in the level density (LD) parameter, shell correction in the fission barrier ($B_{\mathrm{f}}$), the effect of the orientation degree of freedom of the CN spin ($K_{\mathrm{or}}$), collective enhancement of level density (CELD), and dissipation in fission. Input parameters are not tuned to reproduce observables from specific reaction(s) and the reduced dissipation coefficient ($\beta$) is treated as the only adjustable parameter. Calculated evaporation residue (ER) cross sections (${\sigma }_{\mathrm{ER}}$), fission cross sections (${\sigma }_{\mathrm{fiss}}$), and particle, i.e., neutron, proton, and $\alpha$ particle, multiplicities are compared with data covering $A_{\mathrm{CN}}=156$–248.

Results: The model produces reasonable fits to ER and fission excitation functions for all the reactions considered in this work. Pre-scission neutron multiplicities (${\nu }_{\mathrm{pre}}$) are underestimated by the calculation beyond $A_{\mathrm{CN}}\sim 200$. An increasingly higher value of $\beta$, in the range of 2–$4\times {10}^{21}{\mathrm{s}}^{-1}$, is required to reproduce the data with increasing $A_{\mathrm{CN}}$. Proton and $\alpha$-particle multiplicities, measured in coincidence with both ERs and fission fragments, are in qualitative agreement with model predictions.

Conclusions: The present work mitigates the existing inconsistencies in modeling statistical decay of the fissile CN to a large extent. Contradictory requirements of fission enhancement—obtained by scaling down the fission barrier to reproduce ${\sigma }_{\mathrm{ER}}$ or ${\sigma }_{\mathrm{fiss}}$ and fission suppression realized by introducing dissipation in the fission channel to reproduce ${\nu }_{\mathrm{pre}}$, for similar reactions—have now become redundant. There are scopes for further refinement of the model, as is evident from the mismatch between measured and calculated particle multiplicities in a few cases.

Background: Predicting the properties of neutron-rich nuclei far from the valley of stability is one of the major challenges of modern nuclear theory. In heavy and superheavy nuclei, a difference of only a few neutrons is sufficient to change the dominant fission mode. A theoretical approach capable of predicting such rapid transitions for neutron-rich systems would be a valuable tool to better understand $r$-process nucleosynthesis or the decay of superheavy elements.

Purpose: In this work, we investigate for the first time the transition from asymmetric to symmetric fission through the calculation of primary fission yields with the time-dependent generator coordinate method (TDGCM). We choose here the transition in neutron-rich fermium isotopes, which was the first to be observed experimentally in the late 1970s and is often used as a benchmark for theoretical studies.

Methods: We compute the primary fission fragment mass and charge yields for ${}^{254}\mathrm{Fm}, {}^{256}\mathrm{Fm}$, and ${}^{258}\mathrm{Fm}$ from the TDGCM under the Gaussian overlap approximation. The static part of the calculation (generation of a potential energy surface) consists of a series of constrained Hartree-Fock-Bogoliubov calculations based on the D1S, D1M, or D1N parametrization of the Gogny effective interaction in a two-center harmonic oscillator basis. The two-dimensional dynamics in the collective space spanned by the quadrupole and octupole moments $({\widehat{Q}}_{20},{\widehat{Q}}_{30})$ is then computed with the finite element solver Felix-2.0.

Results: The available experimental data and the TDGCM post-dictions are consistent and agree especially on the position in the fermium isotopic chain at which the transition occurs. In addition, the TDGCM predicts two distinct asymmetric modes for the fission of ${}^{254}\mathrm{Fm}$.

Conclusions: Thanks to its intrinsic accounting of shell effects and to its ability to describe the dynamics of the system up to configurations close to scission, the TDGCM is able to describe qualitatively the fission yield transition in the neutron-rich fermium isotopes. This makes it a promising tool to study the evolution of the fission yields far from the valley of stability. The main limitation of the method lies in the presence of discontinuities in the two-dimensional manifold of generator states.

A $\gamma$-decaying isomeric state (${\tau }_{1/2}={197}_{-17}^{+19}$ ns) has been identified in ${}^{96}\mathrm{Cd}$, which is one $\alpha$ particle away from the last known bound $N=Z$ nucleus, ${}^{100}\mathrm{Sn}$. Comparison of the results with shell-model calculations has allowed a tentative experimental level scheme to be deduced and the isomer to be interpreted as a medium-spin negative-parity spin trap based on the coupling of isoscalar ($T=0$) and isovector ($T=1$) neutron-proton pairs. The data also suggest evidence for the population of a $9^{+}$ $T=1$ state, which is predicted by shell-model calculations to be yrast. Such a low-lying $T=1$ state, which is unknown in lighter mass even-even self-conjugate nuclei, can also be interpreted in terms of the coupling of $T=0$ and $T=1$ neutron-proton pairs.

Excited states in ${}^{58,60,62}\mathrm{Ni}$ were populated via inelastic proton scattering at the Australian National University as well as via inelastic neutron scattering at the University of Kentucky Accelerator Laboratory. The Super-e electron spectrometer and the CAESAR Compton-suppressed HPGe array were used in complementary experiments to measure conversion coefficients and $\delta (E2/M1)$ mixing ratios, respectively, for a number of $2^{+}\to 2^{+}$ transitions. The data obtained were combined with lifetimes and branching ratios to determine $E0,M1$, and $E2$ transition strengths between $2^{+}$ states. The $E0$ transition strengths between $0^{+}$ states were measured using internal conversion electron spectroscopy and compare well to previous results from internal pair formation spectroscopy. The $E0$ transition strengths between the lowest-lying $2^{+}$ states were found to be consistently large for the isotopes studied.

The role of three-body force (TBF) and the relativistic corrections (RC) on the equations of state of nuclear matter and $\beta$-stable matter (BSM) within the relativistic lowest-order constrained variation (RLOCV) approach are studied. The AV14 potential and its relativistic version $\left({\tilde{v}}_{14}\right)$ as well as the AV18 potential are considered as the bare two-body potentials by employing the nuclear many-body Hamiltonian. It is shown that by using ${\tilde{v}}_{14}$, all properties of cold nuclear matter can be correctly reproduced if TBF is used in RLOCV framework. The energy and proton abundance of BSM are calculated for a wide range of baryon number densities, which are of interest in astrophysics. It is also shown that by adding RC or TBF to our calculations, the maximum proton abundance is pushed toward lower densities. Furthermore, the particle number densities decrease by including RC and increase when TBF is added to the interactions. The opposite behaviors for the role TBF and RC on saturation properties of nuclear matter as well as proton number densities of nuclear $\beta$-stable matter are found. It is also shown that the effects of three-body forces are much larger than those of relativistic corrections.

Different models for the nonlocal description of the nuclear interaction are compared through a study of their effects on the half-lives of radioactive nuclei decaying by the emission of alpha particles. The half-lives are evaluated by considering a preformed $\alpha$ particle (${}^4\mathrm{He}$ nucleus), which tunnels through the Coulomb barrier generated by its interaction with the daughter nucleus. An effective potential obtained from a density-dependent double-folding strong potential between the $\alpha$ and the daughter nucleus within the nonlocal framework is found to decrease the half-lives as compared to those in the absence of nonlocalities. Whereas the percentage decrease within the older Perey-Buck and São Paulo models ranges between 20 to 40% for medium to heavy nuclei, a recently proposed effective potential leads to a decrease of only 2 to 4%. In view of these results, we provide a closer examination of the approximations used in deriving the local equivalent potentials and propose that, apart from the scattering data, the $\alpha$ decay half-lives can be used as a complementary tool for constraining the nonlocality models.

The problems of reliability of partial photoneutron cross-section data for ${}^{75}\mathrm{As}$ obtained using beams of quasimonoenergetic photons produced by annihilation in flight of relativistic positrons and the method of neutron multiplicity sorting at Lawrence Livermore National Laboratory (USA) and Centre d’Etudes Nucleaires of Saclay (France) were discussed using the objective physical data reliability criteria. New data for photoneutron reaction cross sections for ${}^{75}\mathrm{As}$, satisfying those criteria, were obtained using the experimental-theoretical method for partial reaction cross-section evaluating. Evaluated data for ${}^{75}\mathrm{As}$ were compared with experimental data and the problems of significant disagreements between Livermore and Saclay data were discussed in detail. It was shown that experimental data for the $(\gamma ,1n)$ and $(\gamma ,2n)$ reactions’ cross sections obtained at Livermore are not reliable because of significant systematic uncertainties of different nature.

Photoneutron cross sections were measured for ${}^{203}\mathrm{Tl}$ and ${}^{205}\mathrm{Tl}$ at energies between the one- and two-neutron thresholds using quasimonochromatic $\gamma$-ray beams produced in laser Compton scattering at the NewSUBARU synchrotron radiation facility. Our measurement results in cross sections significantly different from the previously reported bremsstrahlung experiment, leading to rather different giant dipole resonance (GDR) parameters, in particular to lower GDR peak energies and higher peak cross sections. The photoneutron data are used to constrain the $\gamma$-ray strength function on the basis of the Hartree-Fock-Bogolyubov plus quasiparticle random-phase approximation using the Gogny D1M interaction. Supplementing the experimentally constrained $\gamma$-ray strength function with the zero-limit $E1$ and $M1$ contributions for the de-excitation mode, we estimate the Maxwellian-averaged cross section for the s-process branching-point nucleus ${}^{204}\mathrm{Tl}$ in the context of the ${}^{205}\mathrm{Pb}-{}^{205}\mathrm{Tl}$ chronometry.

The noncongruent liquid-gas phase transition (LGPT) in asymmetric nuclear matter is studied using the recently developed quantum van der Waals model in the grand canonical ensemble. Different values of the electric-to-baryon charge ratio, $Q/B$, are considered. This noncongruent LGPT exhibits several features which are not present in the congruent LGPT of symmetric nuclear matter. These include a continuous phase transformation, a change in the location of the critical point, and the separation of the critical point and the endpoints. The effects which are associated with the noncongruent LGPT become negligible for the following cases: when $Q/B$ approaches its limiting values, 0.5 or 0, or if isospin dependence of nucleon-nucleon interaction and quantum statistical effects can be neglected. The latter situation is realized when the particle degeneracy attains large values, $g\gtrsim 10$.

The centrality dependence of rapidity distributions of pions in Pb+Pb reactions can be understood by imposing local energy-momentum conservation in the longitudinal “fire streaks” of excited matter. With no tuning nor adjustment to the experimental data, the rapidity distribution of pions produced by the fire streak which we obtained from Pb+Pb collisions reproduces the shape of the experimental pion rapidity distribution in $p+p$ interactions, measured by the NA49 Collaboration at the same energy. The observed difference in the absolute normalization of this distribution can be explained by the difference in the overall energy balance, induced by baryon stopping and strangeness enhancement phenomena occurring in heavy ion collisions. We estimate such effects using a collection of Super Proton Synchrotron experimental data on ${\pi }^{\pm }, K^{\pm }$, net $p$, and $n$ production in $p+p$ and Pb+Pb reactions. Implications of the above findings are discussed.