Starting from realistic nuclear forces, the chiral ${\mathrm{N}}^3\mathrm{LO}$ and JISP16, we have applied many-body perturbation theory (MBPT) to the structure of closed-shell nuclei, ${}^4\mathrm{He}$ and ${}^{16}\mathrm{O}$. The two-body ${\mathrm{N}}^3\mathrm{LO}$ interaction is softened by a similarity renormalization group transformation while JISP16 is adopted without renormalization. The MBPT calculations are performed within the Hartree-Fock (HF) bases. The angular momentum coupled scheme is used, which can reduce the computational task. Corrections up to the third order in energy and up to the second order in radius are evaluated. Higher-order corrections in the HF basis are small relative to the leading-order perturbative result. Using the antisymmetrized Goldstone diagram expansions of the wave function, we directly correct the one-body density for the calculation of the radius, rather than calculate corrections to the occupation probabilities of single-particle orbits as found in other treatments. We compare our results with other methods where available and find good agreement. This supports the conclusion that our methods produce reasonably converged results with these interactions. We also compare our results with experimental data.

Valuable theoretical predictions of nuclear dipole excitations in the whole chart are of great interest for different nuclear applications, including in particular nuclear astrophysics. Here we present large-scale calculations of the $E1\gamma$-ray strength function obtained in the framework of the axially symmetric deformed quasiparticle random-phase approximation based on the finite-range Gogny force. This approach is applied to even-even nuclei, the strength function for odd nuclei being derived by interpolation. The convergence with respect to the adopted number of harmonic oscillator shells and the cutoff energy introduced in the 2-quasiparticle $(2-qp)$ excitation space is analyzed. The calculations performed with two different Gogny interactions, namely D1S and D1M, are compared. A systematic energy shift of the $E1$ strength is found for D1M relative to D1S, leading to a lower energy centroid and a smaller energy-weighted sum rule for D1M. When comparing with experimental photoabsorption data, the Gogny-QRPA predictions are found to overestimate the giant dipole energy by typically $\sim 2$ MeV. Despite the microscopic nature of our self-consistent Hartree-Fock-Bogoliubov plus QRPA calculation, some phenomenological corrections need to be included to take into account the effects beyond the standard $2-qp$ QRPA excitations and the coupling between the single-particle and low-lying collective phonon degrees of freedom. For this purpose, three prescriptions of folding procedure are considered and adjusted to reproduce experimental photoabsorption data at best. All of them are shown to lead to somewhat similar predictions of the $E1$ strength, both at low energies and for exotic neutron-rich nuclei. Predictions of $\gamma$-ray strength functions and Maxwellian-averaged neutron capture rates for the whole Sn isotopic chain are also discussed and compared with previous theoretical calculations.

Background: Complete fusion cross section measurements involving weakly bound projectiles show suppression at above-barrier energies compared to coupled-channels (CC) calculations, but no definite conclusion could be drawn for sub-barrier energies. Different CC models often lead to contrasting results.

Purpose: We aim to investigate the differences in the fusion cross sections predicted by commonly used CC calculations, using codes such as fresco and ccfull, when compared to experimental data.

Methods: The fusion cross sections are normalized to a dimensionless form by isolating the effect of only dynamic channel couplings calculated by both fresco and ccfull, by the method of fusion functions, and compared to a universal fusion function. This acts as a probe for obtaining the model dependence of fusion.

Results: A difference is observed between the predictions of fresco and ccfull for all the reactions involving ${}^{6,7}\mathrm{Li}$ as projectiles, and it is noticeably more for systems involving ${}^7\mathrm{Li}$.

Conclusions: With the theoretical foundations of the two CC models being different, their calculation of fusion is different even for the same system. The conclusion about the enhancement or suppression of fusion cross sections is model dependent.

Elastic scattering measurements were performed for the ${}^7\mathrm{Li}+p$ system in inverse kinematics at energies of 16, 25, 35, and 38.1 MeV and for the ${}^7\mathrm{Li}+d$ system at 38.1 MeV. The heavy ejectiles were detected by the large acceptance MAGNEX spectrometer at the Laboratori Nazionali del Sud in Catania, Italy. The results are analyzed using the Jeukenne-Lejeune-Mahaux and continuum discretized coupled channel frameworks. In the latter case the cluster structure of ${}^7\mathrm{Li}$ proves to be critical for the theoretical interpretation of the experimental results.

We calculate the triangular flow parameter $v_3$ of thermal photons from an event-by-event ideal hydrodynamic model for 0–40% central collisions of Pb nuclei at $\sqrt{s_{NN}}=2.76$ TeV at the CERN Large Hadron Collider. $v_3$ determined with respect to the participant plane (PP) is found to be nonzero and positive, and its $p_T$ dependence is qualitatively similar to the elliptic flow parameter $v_2$(PP) of thermal photons in the range $1\le p_T\le 6\text{GeV}/c$. In the range $p_T\le 3\text{GeV}/c$, $v_3$(PP) is found to be about 50–75% of $v_2$(PP) and for $p_T>3\text{GeV}/c$ the two anisotropy parameters become comparable. The value of $v_3$ is driven by local density fluctuations both directly via the creation of triangular geometry and indirectly via additional flow. As expected, the triangular flow parameter calculated with respect to the reaction plane $v_3$(RP) is found to be close to zero. We show that $v_3$(PP) strongly depends on the spatial size of fluctuations, especially in the higher $p_T(\ge 3\mathrm{GeV}/c)$ region where a larger value of $\sigma$ results in a smaller $v_3\left(\mathrm{PP}\right)$. In addition, $v_3\left(\mathrm{PP}\right)$ is found to increase with the assumed formation time of the thermalized system.

We extend the ab initio coupled-cluster effective interaction (CCEI) method to open-shell nuclei with protons and neutrons in the valence space and compute binding energies and excited states of isotopes of neon and magnesium. We employ a nucleon-nucleon and three-nucleon interaction from chiral effective field theory evolved to a lower cutoff via a similarity renormalization group transformation. We find good agreement with experiment for binding energies and spectra, while charge radii of neon isotopes are underestimated. For the deformed nuclei ${}^{20}\mathrm{Ne}$ and ${}^{24}\mathrm{Mg}$, we reproduce rotational bands and electric quadrupole transitions within uncertainties estimated from an effective field theory for deformed nuclei, thereby demonstrating that collective phenomena in $sd$-shell nuclei emerge from complex ab initio calculations.

Charge-changing cross sections at high energies are expected to provide useful information on nuclear charge radii. No reliable theory to calculate the cross section has yet been available. We develop a formula using Glauber and eikonal approximations and test its validity with recent new data on carbon isotopes measured at around $900A$ MeV. We first confirm that our theory reproduces the cross sections of ${}^{12,13,14}\mathrm{C}+{}^{12}\mathrm{C}$ consistently with the known charge radii. Next we show that the cross sections of ${}^{12-19}\mathrm{C}$ on a proton target are all well reproduced provided the role of neutrons is accounted for. We also discuss the energy dependence of the charge-changing cross sections.

The $\alpha$ cluster states are discussed in a model frame of extended quantum molecular dynamics. Different $\alpha$ cluster structures are studied in detail, such as ${}^8\mathrm{Be}$ two-$\alpha$ cluster structure, ${}^{12}\mathrm{C}$ triangle structure, ${}^{12}\mathrm{C}$ chain structure, ${}^{16}\mathrm{O}$ chain structure, ${}^{16}\mathrm{O}$ kite structure, and ${}^{16}\mathrm{O}$ square structure. The properties studied include the width of wave packets for different $\alpha$ clusters, momentum distribution, and the binding energy among $\alpha$ clusters. We also discuss how the $\alpha$ cluster degree of freedom affects nuclear collective vibrations. The cluster configurations in ${}^{12}\mathrm{C}$ and ${}^{16}\mathrm{O}$ are found to have corresponding characteristic spectra of giant dipole resonance (GDR), and the coherences of different $\alpha$ clusters' dipole oscillations are described in detail. The geometrical and dynamical symmetries of $\alpha$-clustering configurations are responsible for the number and centroid energies of peaks of GDR spectra. Therefore, the GDR can be regarded as an effective probe to diagnose different $\alpha$ cluster configurations in light nuclei.

We propose a simple approach to measure the energy of the few-eV isomeric state in ${}^{229}\mathrm{Th}$. To this end, ${}^{233}\mathrm{U}$ nuclei are doped into VUV-transparent crystals, where they undergo $\alpha$ decay into ${}^{229}\mathrm{Th}$, and, with a probability of 2%, populate the isomeric state. These ${}^{229\mathrm{m}}\mathrm{Th}$ nuclei may decay into the nuclear ground state under emission of the sought-after VUV $\gamma$ ray, whose wavelength can be determined with a spectrometer. Based on measurements of the optical transmission of ${}^{238}\mathrm{U}$:${\mathrm{CaF}}_2$ crystals in the VUV range, we expect a signal at least two orders of magnitude larger compared to current schemes using surface implantation of recoil nuclei. The signal background is dominated by Cherenkov radiation induced by $\beta$ decays of the thorium decay chain. We estimate that, even if the isomer undergoes radiative de-excitation with a probability of only 0.1%, the VUV $\gamma$ ray can be detected within a reasonable measurement time.

Background: It is well known that the anomalous behavior of angular anisotropies of fission fragments at sub- and near-barrier energies is associated with a memory of conditions in the entrance channel of the heavy-ion reactions, particularly, deformations and spins of colliding nuclei that determine the initial distributions for the components of the total angular momentum over the symmetry axis of the fissioning system and the beam axis.

Purpose: We develop a new dynamic approach, which allows the description of the memory effects in the fission fragment angular distributions and provides new information on fusion and fission dynamics.

Methods: The approach is based on the dynamic model of the fission fragment angular distributions which takes into account stochastic aspects of nuclear fission and thermal fluctuations for the tilting mode that is characterized by the projection of the total angular momentum onto the symmetry axis of the fissioning system. Another base of our approach is the quantum mechanical method to calculate the initial distributions over the components of the total angular momentum of the nuclear system immediately following complete fusion.

Results: A method is suggested for calculating the initial distributions of the total angular momentum projection onto the symmetry axis for the nuclear systems formed in the reactions of complete fusion of deformed nuclei with spins. The angular distributions of fission fragments for the ${}^{16}\mathrm{O}+{}^{232}\mathrm{Th},{}^{12}\mathrm{C}+{}^{235,236,238}\mathrm{U}$, and ${}^{13}\mathrm{C}+{}^{235}\mathrm{U}$ reactions have been analyzed within the dynamic approach over a range of sub- and above-barrier energies. The analysis allowed us to determine the relaxation time for the tilting mode and the fraction of fission events occurring in times not larger than the relaxation time for the tilting mode.

Conclusions: It is shown that the memory effects play an important role in the formation of the angular distributions of fission fragments for the reactions induced by heavy ions. The approach developed for analysis of the effects is a suitable tool to get insight into the complete fusion-fission dynamics, in particular, to investigate the mechanism of the complete fusion and fission time scale.

We analyzed the $\varphi$ meson production in central Ni + Ni collisions at a beam kinetic energy of 1.93A GeV with the FOPI spectrometer and found a production probability per event of $[8.6\pm 1.6\left(\text{stat}\right)\pm 1.5\left(\text{syst}\right)]\times {10}^{-4}$. This new data point allows us for the first time to inspect the centrality dependence of subthreshold $\varphi$ meson production in heavy-ion collisions. The rise of $\varphi$ meson multiplicity per event with mean number of participants can be parametrized by a power function with exponent $\alpha =1.8\pm 0.6$. The ratio of $\varphi$ to $K^{-}$ production yields seems not to depend, within the experimental uncertainties, on the collision centrality, and the average of measured values was found to be $0.36\pm 0.05$.

We explore predictions of the wounded-quark model for particle production and properties of the initial state formed in ultrarelativistic heavy-ion collisions. The approach is applied uniformly to $A+A$ collisions in a wide collision energy range, as well as for $p+A$ and $p+p$ collisions at the CERN Large Hadron Collider (LHC). We find that generically the predictions from wounded quarks for such features as eccentricities or initial sizes are close (within 15%) to predictions of the wounded nucleon model with an amended binary component. A larger difference is found for the size in $p+\text{Pb}$ system, where the wounded-quark model yields a smaller (more compact) initial fireball than the standard wounded-nucleon model. The inclusion of subnucleonic degrees of freedom allows us to analyze $p+p$ collisions in an analogous way, with predictions that can be used in further collective evolution. The approximate linear dependence of particle production in $A+A$ collisions on the number of wounded quarks, as found in previous studies, makes the approach based on wounded quarks natural. Importantly, at the LHC energies we find approximate uniformity in particle production from wounded quarks, where at a given collision energy per nucleon pair similar production of initial entropy per source is needed to explain the particle production from $p+p$ collisions up to $A+A$ collisions. We also discuss the sensitivity of the wounded-quark model predictions to distribution of quarks in nucleons, distribution of nucleons in nuclei, and the quark-quark inelasticity profile in the impact parameter. In our procedure, the quark-quark inelasticity profile is chosen in such a way that the experiment-based parametrization of the proton-proton inelasticity profile is properly reproduced. The parameters of the overlaid multiplicity distribution are fixed from $p+p$ and $p+\text{Pb}$ data.

It has been generally accepted that momentum-dependent potentials for neutrons and protons at energies well away from the Fermi surface cause both to behave as if their inertial masses are effectively 70% of the vacuum values. This similarity in effective masses may no longer hold in dense neutron-rich regions within neutron stars, core-collapse supernovas, and nuclear collisions. There differences in the momentum-dependent symmetry potentials may cause neutron and proton effective masses to differ significantly. We investigate this effect by measuring the energy spectra of neutrons, protons, and charged particles emitted in ${}^{112}\mathrm{Sn}+{}^{112}\mathrm{Sn}$ and ${}^{124}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ collisions at $E_{\mathrm{beam}}/A=50$ and 120 MeV with precision sufficient to distinguish, in principle, between effective interactions with very different values of the neutron and proton effective masses. These data and model comparisons point the way towards future advances in our capabilities to understand the density and momentum dependence of the nuclear symmetry energy.

This paper suggests that a change in the lifetime of the $\alpha$-decay process in ${}^{241}\mathrm{Am}$ may be detected at high pressures achievable in the laboratory, essentially, due to the extraordinary high compressibility of Am at the megabar range. The Thomas-Fermi model was used to calculate the effect of high pressure on the atomic electron density and the variation of the atomic potential of ${}^{241}\mathrm{Am}$. It was found that at pressures of about 0.5 Mbar the relative change in the lifetime of ${}^{241}\mathrm{Am}$ is about $-2\times {10}^{-4}$. Detailed experimental procedures to measure this effect by compressing the ${}^{241}\mathrm{Am}$ metal in a diamond-anvil cell are presented where diagnostics is based on counting of the 60-keV γ rays accompanying the α decay and/or mass spectrometry on the ${}^{237}\mathrm{Np}/{}^{241}\mathrm{Am}$ isotope ratio.

In this work we have studied $T_z=+2\to +1$, Gamow-Teller (GT) transitions in the ${}^{48}\mathrm{Ti}({}^3\mathrm{He},t){}^{48}\mathrm{V}$ charge-exchange reaction at 140 MeV/nucleon and $0^{\circ }$ at the Research Center for Nuclear Physics, Osaka. From the high-resolution facility, consisting of a high-dispersion beamline and the Grand Raiden spectrometer, the spectrum had an energy resolution of 21 keV, among the best achieved. Individual GT transitions were observed and GT strength was derived for each state populated up to an excitation energy of 12 MeV. The total sum of the $B$(GT) strength observed in discrete states was 4.0, which is 33% of the sum-rule-limit value of 12. The results were compared with the results of shell-model calculations carried out with the GXPF1J interaction. The measured $B$(GT) distribution was also compared with that obtained in the $\left({}^3\mathrm{He},t\right)$ charge-exchange reaction on ${}^{47}\mathrm{Ti}$. On the assumption of isospin symmetry the $\beta$ spectrum of the $T_z=-2$ nucleus ${}^{48}\mathrm{Fe}$ was deduced from the observed spectrum in the ${}^{48}\mathrm{Ti}({}^3\mathrm{He},t){}^{48}\mathrm{V}$ reaction and this predicted spectrum was compared with the measured one.

Large-scale shell-model calculations are performed for even-even, odd-mass, and doubly odd nuclei of Pb, Bi, Po, At, Rn, and Fr isotopes in the neutron deficit region $\left(Z\ge 82,N\le 126\right)$ assuming ${}^{208}\mathrm{Pb}$ as a doubly magic core. All the six single-particle orbitals between the magic numbers 82 and 126, namely, $0h_{9/2},1f_{7/2},0i_{13/2},2p_{3/2},1f_{5/2}$, and $2p_{1/2}$, are considered. For a phenomenological effective two-body interaction, one set of the monopole pairing and quadrupole-quadrupole interactions including the multipole-pairing interactions is adopted for all the nuclei considered. The calculated energies and electromagnetic properties are compared with the experimental data. Furthermore, many isomeric states are analyzed in terms of the shell-model configurations.

We present a procedure that is helpful to reduce the computational complexity of large-scale shell-model calculations, by preserving as much as possible the role of the rejected degrees of freedom in an effective approach. Our truncation is driven first by the analysis of the effective single-particle energies of the original large-scale shell-model Hamiltonian, in order to locate the relevant degrees of freedom to describe a class of isotopes or isotones, namely the single-particle orbitals that will constitute a new truncated model space. The second step is to perform a unitary transformation of the original Hamiltonian from its model space into the truncated one. This transformation generates a new shell-model Hamiltonian, defined in a smaller model space, that retains effectively the role of the excluded single-particle orbitals. As an application of this procedure, we have chosen a realistic shell-model Hamiltonian defined in a large model space, set up by seven proton and five neutron single-particle orbitals outside ${}^{88}\mathrm{Sr}$. We study the dependence of shell-model results upon different truncations of the original model space for the Zr, Mo, Ru, Pd, Cd, and Sn isotopic chains, showing the reliability of this truncation procedure.

Two-particle pseudorapidity correlations are analyzed in a simple model, where in the initial stage of the reaction multiple sources, extended in rapidity, are created. We show how the fluctuations of the length of the sources in rapidity generate correlations in the initial entropy deposition, which later contribute to the observed longitudinal correlations in hadron production. Our analysis, which is analytic and leads to straightforward formulas, allows us to understand the structure of the correlations, in particular to identify the component related to the fluctuation of the numbers of sources and the component from the length fluctuations. We also present the results in terms of the expansion in the basis of the Legendre polynomials. A number of further effects are discussed, such as smearing of the pseudorapidity distributions or resonance decays. Our results reproduce qualitatively and semiquantitatively the basic features of the recent measurements at the LHC.

We study the electroweak properties of ground state octet baryons in a relativistic quark-spectator-diquark model, with a light-front formalism applied to take relativistic effects into account. Our model provides a consistent picture of the electroweak properties of the ground state octet baryons in the low momentum transfer region. The Melosh-Wigner rotation is applied as the transformation relation between spinors in the instant form and front form. Numerical results are presented for the magnetic moments, weak transition charges, and Sachs form factors. Our results are in good agreement with experimental measurements and other theoretical results.

Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on ${}^{20,21}\mathrm{N}$ are reported. Relativistic ${}^{20,21}\mathrm{N}$ ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the ${}^{19}\mathrm{N}(n,\gamma ){}^{20}\mathrm{N}$ and ${}^{20}\mathrm{N}(n,\gamma ){}^{21}\mathrm{N}$ excitation functions and thermonuclear reaction rates have been determined. The ${}^{19}\mathrm{N}(n,\gamma ){}^{20}\mathrm{N}$ rate is up to a factor of 5 higher at $T<1\mathrm{GK}$ with respect to previous theoretical calculations, leading to a 10% decrease in the predicted fluorine abundance.