The astrophysical ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ and ${}^3\mathrm{H}(\alpha ,\gamma ){}^7\mathrm{Li}$ direct capture processes are studied in the framework of the two-body model with potentials of a simple Gaussian form, which describe correctly the phase shifts in the $s$, $p$, $d$, and $f$ waves, as well as the binding energy and the asymptotic normalization constant of the ground $p_{3/2}$ and the first excited $p_{1/2}$ bound states. It is shown that the $E1$ transition from the initial $s$ wave to the final $p$ waves is strongly dominant in both capture reactions. On this basis the $s$-wave potential parameters are adjusted to reproduce the new data of the LUNA Collaboration around 100 keV and the newest data at the Gamov peak estimated with the help of the observed neutrino fluxes from the sun, $S_{34}\left({23}_{-5}^{+6}\mathrm{keV}\right)=0.548\pm 0.054$ keV b for the astrophysical $S$ factor of the capture process ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$. The resulting model describes well the astrophysical $S$ factor in the low-energy big-bang nucleosynthesis region of 180–400 keV; however, it has a tendency to underestimate the data above 0.5 MeV. The energy dependence of the $S$ factor is mostly consistent with the data and the results of the no-core shell model with continuum, but substantially different from the fermionic molecular dynamics model predictions. Two-body potentials, adjusted for the properties of the ${}^7\mathrm{Be}$ nucleus, ${}^3\mathrm{He}+\alpha$ elastic scattering data, and the astrophysical $S$ factor of the ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ direct capture reaction, are able to reproduce the properties of the ${}^7\mathrm{Li}$ nucleus, the binding energies of the ground $3/2^{-}$ and first excited $1/2^{-}$ states, and phase shifts of the ${}^3\mathrm{H}+\alpha$ elastic scattering in partial waves. Most importantly, these potential models can successfully describe both absolute value and energy dependence of the existing experimental data for the mirror astrophysical ${}^3\mathrm{H}(\alpha ,\gamma ){}^7\mathrm{Li}$ capture reaction without any additional adjustment of the parameters.

Applying the evolutionary model-independent $S$-matrix approach, we show that a simultaneous correct description of the ${}^4\mathrm{He}-{}^{40}\mathrm{Ca}$ elastic scattering patterns observed in going from anomalous large-angle scattering to near-Coulomb-barrier scattering (NCBS) can be achieved in a unified way using $S$-matrix moduli and real parts of nuclear phase, which are smooth and monotonic functions of an angular momentum, while quantum deflection functions retain a form characteristic of the nuclear rainbow case. Mechanism of NCBS pattern formation and transformation of the pattern into a pure Coulomb scattering pattern with decreasing energy in the presence of strong nuclear refraction is revealed.

Adopting hyperon-nucleon and hyperon-nucleon-nucleon interactions parametrized in chiral effective field theory, single-particle potentials of the $\mathrm{\Lambda }$ and $\mathrm{\Sigma }$ hyperons are evaluated in symmetric nuclear matter and in pure neutron matter within the framework of lowest-order Bruckner theory. The chiral NLO interaction bears strong $\mathrm{\Lambda }N-\mathrm{\Sigma }N$ coupling. Although the $\mathrm{\Lambda }$ potential is repulsive if the coupling is switched off, the $\mathrm{\Lambda }N-\mathrm{\Sigma }N$ correlation brings about the attraction consistent with empirical data. The $\mathrm{\Sigma }$ potential is repulsive, which is also consistent with empirical information. The interesting result is that the $\mathrm{\Lambda }$ potential becomes shallower beyond normal density. This provides the possibility of solving the hyperon puzzle without introducing ad hoc assumptions. The effects of the $\mathrm{\Lambda }NN-\mathrm{\Lambda }NN$ and $\mathrm{\Lambda }NN-\mathrm{\Sigma }NN$ three-baryon forces are considered. These three-baryon forces are first reduced to normal-ordered effective two-baryon interactions in nuclear matter and then incorporated in the $G$-matrix equation. The repulsion from the $\mathrm{\Lambda }NN-\mathrm{\Lambda }NN$ interaction is of the order of 5 MeV at normal density and becomes larger with increasing density. The effects of the $\mathrm{\Lambda }NN-\mathrm{\Sigma }NN$ coupling compensate the repulsion at normal density. The net effect of the three-baryon interactions on the $\mathrm{\Lambda }$ single-particle potential is repulsive at higher densities.

Background: A fairly rich amount of experimental spectroscopic data have disclosed intriguing properties of the nuclei in the region of neutron rich oxygen isotopes up to the neutron dripline. They, therefore, represent a unique laboratory for studying the evolution of nuclear structure away from the stability line.

Purpose: We intend to give an exhaustive microscopic description of low and high energy spectra, dipole response, weak, and electromagnetic properties of the even ${}^{22}\mathrm{O}$ and the odd ${}^{23}\mathrm{O}$ and ${}^{23}\mathrm{F}$.

Method: An equation of motion phonon method generates an orthonormal basis of correlated $n$-phonon states ($n=0,1,2,\cdots$) built of constituent Tamm-Dancoff phonons. This basis is adopted to solve the full eigenvalue equations in even nuclei and to construct an orthonormal particle-core basis for the eigenvalue problem in odd nuclei. No approximations are involved and the Pauli principle is taken into full account. The method is adopted to perform self-consistent, parameter free, calculations using an optimized chiral nucleon-nucleon interaction in a space encompassing up to two-phonon basis states.

Results: The computed spectra in ${}^{22}\mathrm{O}$ and ${}^{23}\mathrm{O}$ and the dipole cross section in ${}^{22}\mathrm{O}$ are in overall agreement with the experimental data. The calculation describes poorly the spectrum of ${}^{23}\mathrm{F}$.

Conclusions: The two-phonon configurations play a crucial role in the description of spectra and transitions. The large discrepancies concerning the spectra of ${}^{23}\mathrm{F}$ are ultimately traced back to the large separation between the Hartree-Fock levels belonging to different major shells. We suggest that a more compact single particle spectrum is needed and can be generated by a new chiral potential which includes explicitly the contribution of the three-body forces.

In the framework of the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model, sensitive regions of some nucleon observables to the nuclear symmetry energy are studied. It is found that the symmetry-energy-sensitive observable $n/p$ ratio in the ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ reaction at 0.3 GeV/nucleon in fact just probes the density-dependent symmetry energy below the density of $1.5{\rho }_0$ and effectively probes the density-dependent symmetry energy around or somewhat below the saturation density. Nucleon elliptic flow can probe the symmetry energy from the low-density region to the high-density region when changing the incident beam energies from 0.3 to 0.6 GeV/nucleon in the semi-central ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ reaction. And nucleon transverse and elliptic flows in the semi-central ${}^{197}\mathrm{Au}+{}^{197}\mathrm{Au}$ reaction at 0.6 GeV/nucleon are more sensitive to the high-density behavior of the nuclear symmetry energy. One thus concludes that nucleon observables in the heavy reaction system and with higher incident beam energy are more suitable to be used to probe the high-density behavior of the symmetry energy. The present study may help one to get more specific information about the density-dependent symmetry energy from nucleon flow observable in heavy-ion collisions at intermediate energies.

Emission of two neutrons or two protons in reactions and decays is often discussed in terms of “dineutron” or “diproton” emission. The discussion often leans intuitively on something described by Migdal-Watson approximation. In this work we propose a way to formalize situations of dineutron emission. It is demonstrated that properly formally defined dineutron emission may reveal properties which are drastically different from those traditionally expected, and properties which are actually observed in three-body decays.

Recent lattice QCD data on higher order susceptibilities of charm quarks provide the opportunity to explore charm quark equilibration in the early quark gluon plasma (QGP) phase. Here, we propose to use the lattice data on second- and fourth-order net charm susceptibilities to infer the charm quark equilibration temperature and the corresponding volume, in the early QGP stage, via a combined analysis of experimentally measured multiplicity fluctuations. Furthermore, the first perturbative results for the second- and fourth-order charm quark susceptibilities and their ratio are presented.

We calculate the form factors of the electromagnetic nucleon-to-$\mathrm{\Delta }$-resonance transition to third chiral order in manifestly Lorentz-invariant chiral effective field theory. For the purpose of generating a systematic power counting, the complex-mass scheme is applied in combination with the small-scale expansion. We fit the results to available empirical data. To improve our results, we include a contribution of the $\rho$ meson at tree level in a semiphenomenological approach.

Background: The atomic nucleus is a unique laboratory in which to study fundamental aspects of the electroweak interaction. This includes a question concerning in medium renormalization of the axial-vector current, which still lacks satisfactory explanation. Study of spin-isospin or Gamow-Teller (GT) response may provide valuable information on both the quenching of the axial-vector coupling constant as well as on nuclear structure and nuclear astrophysics.

Purpose: We have performed a seminal calculation of the GT response by using the no-core configuration-interaction approach rooted in multireference density functional theory (DFT-NCCI). The model treats properly isospin and rotational symmetries and can be applied to calculate both the nuclear spectra and transition rates in atomic nuclei, irrespectively of their mass and particle-number parity.

Methods: The DFT-NCCI calculation proceeds as follows: First, one builds a configuration space by computing relevant, for a given physical problem, (multi)particle-(multi)hole Slater determinants. Next, one applies the isospin and angular-momentum projections and performs the isospin and $K$ mixing in order to construct a model space composed of linearly dependent states of good angular momentum. Eventually, one mixes the projected states by solving the Hill-Wheeler-Griffin equation.

Results: The method is applied to compute the GT strength distribution in selected $N\approx Z$ nuclei including the $p$-shell ${}^8\mathrm{Li}$ and ${}^8\mathrm{Be}$ nuclei and the $sd$-shell well-deformed nucleus ${}^{24}\mathrm{Mg}$. In order to demonstrate a flexibility of the approach we present also a calculation of the superallowed GT $\beta$ decay in doubly-magic spherical ${}^{100}\mathrm{Sn}$ and the low-spin spectrum in ${}^{100}\mathrm{In}$.

Conclusions: It is demonstrated that the DFT-NCCI model is capable of capturing the GT response satisfactorily well by using a relatively small configuration space, exhausting simultaneously the GT sum rule. The model, due to its flexibility and broad range of applicability, may either serve as a complement or even as an alternative to other theoretical approaches, including the conventional nuclear shell model.

The reaction mechanism of deep-inelastic multinucleon transfer processes in the ${}^{16}\mathrm{O}+{}^{27}\mathrm{Al}$ reaction at an incident ${}^{16}\mathrm{O}$ energy ($E_{\mathrm{lab}}=134$ MeV) substantially above the Coulomb barrier has been studied both experimentally and theoretically. Elastic-scattering angular distribution, total kinetic energy loss spectra, and angular distributions for various transfer channels have been measured. The $Q$-value- and angle-integrated isotope production cross sections have been deduced. To obtain deeper insight into the underlying reaction mechanism, we have carried out a detailed analysis based on the time-dependent Hartree-Fock (TDHF) theory. A recently developed method, TDHF+GEMINI, has been applied to evaluate production cross sections for secondary products. From a comparison between the experimental and theoretical cross sections, we find that the theory qualitatively reproduces the experimental data. Significant effects of secondary light-particle emissions are demonstrated. Possible interplay among fusion-fission, deep-inelastic, multinucleon transfer, and particle evaporation processes is discussed.

The principal component analysis of flow correlations in heavy-ion collisions is studied. The correlation matrix of harmonic flow is generalized to correlations involving several different flow vectors. The method can be applied to study the nonlinear coupling between different harmonic modes in a double differential way in transverse momentum or pseudorapidity. The procedure is illustrated with results from the hydrodynamic model applied to Pb + Pb collisions at $\sqrt{s_{NN}}=2760$ GeV. Three examples of generalized correlations matrices in transverse momentum are constructed corresponding to the coupling of $v_2^2$ and $v_4$, of $v_2{v}_3$ and $v_5$, or of $v_2^3,v_3^3$, and $v_6$. The principal component decomposition is applied to the correlation matrices and the dominant modes are calculated.

We have investigated the cross section for the ${\pi }^{-}p\to K^0\pi \mathrm{\Sigma }$ and $pp\to p{K}^{+}\pi \mathrm{\Sigma }$ reactions, paying attention to a mechanism that develops a triangle singularity. The triangle diagram is realized by the decay of a $N^{*}$ to $K^{*}\mathrm{\Sigma }$ and the $K^{*}$ decay into $\pi K$, and the $\pi \mathrm{\Sigma }$ finally merges into $\mathrm{\Lambda }\left(1405\right)$. The mechanism is expected to produce a peak around $2140\mathrm{MeV}$ in the $K\mathrm{\Lambda }\left(1405\right)$ invariant mass. We found that a clear peak appears around $2100\mathrm{MeV}$ in the $K\mathrm{\Lambda }\left(1405\right)$ invariant mass, which is about $40\mathrm{MeV}$ lower than the expectation, and that is due to the resonance peak of a $N^{*}$ resonance which plays a crucial role in the $K^{*}\mathrm{\Sigma }$ production. The mechanism studied produces the peak of the $\mathrm{\Lambda }\left(1405\right)$ around or below 1400 MeV, as is seen in the $pp\to p{K}^{+}\pi \mathrm{\Sigma }$ HADES experiment.

In view of the recent results of lattice QCD simulation in the $P11$ partial wave that has found no clear signal for the three-quark Roper state we investigate a different mechanism for the formation of the Roper resonance in a coupled channel approach including the $\pi N$, $\pi \mathrm{\Delta }$, and $\sigma N$ channels. We fix the pion-baryon vertices in the underlying quark model while the $s$-wave sigma-baryon interaction is introduced phenomenologically with the coupling strength, the mass, and the width of the $\sigma$ meson as free parameters. The Laurent-Pietarinen expansion is used to extract the information about the $S$-matrix pole. The Lippmann-Schwinger equation for the $K$ matrix with a separable kernel is solved to all orders. For sufficiently strong $\sigma NN$ coupling the kernel becomes singular and a quasibound state emerges at around 1.4 GeV, dominated by the $\sigma N$ component and reflecting itself in a pole of the $S$ matrix. The alternative mechanism involving a ${\left(1s\right)}^{2}2s$ quark resonant state is added to the model and the interplay of the dynamically generated state and the three-quark resonant state is studied. It turns out that for the mass of the three-quark resonant state above 1.6 GeV the mass of the resonance is determined solely by the dynamically generated state, nonetheless, the inclusion of the three-quark resonant state is imperative to reproduce the experimental width and the modulus of the resonance pole.

Background: Nucleosynthesis of mid-mass elements is thought to occur under hot and explosive astrophysical conditions. Radiative $\alpha$ capture on ${}^{34}\mathrm{S}$ has been shown to impact nucleosynthesis in several such conditions, including core and shell oxygen burning, explosive oxygen burning, and type Ia supernovae.

Purpose: Broad uncertainties exist in the literature for the strengths of three resonances within the astrophysically relevant energy range ($E_{\text{CM}}=1.94–3.42\mathrm{MeV}$ at $T=2.2\mathrm{GK}$). Further, there are several states in ${}^{38}\mathrm{Ar}$ within this energy range which have not been previously measured. This work aimed to remeasure the resonance strengths of states for which broad uncertainty existed as well as to measure the resonance strengths and energies of previously unmeasured states.

Methods: Resonance strengths and energies of eight narrow resonances (five of which had not been previously studied) were measured in inverse kinematics with the DRAGON facility at TRIUMF by impinging an isotopically pure beam of ${}^{34}\mathrm{S}$ ions on a windowless ${}^4\mathrm{He}$ gas target. Prompt $\gamma$ emissions of de-exciting ${}^{38}\mathrm{Ar}$ recoils were detected in an array of bismuth germanate scintillators in coincidence with recoil nuclei, which were separated from unreacted beam ions by an electromagnetic mass separator and detected by a time-of-flight system and a multianode ionization chamber.

Results: The present measurements agree with previous results. Broad uncertainty in the resonance strength of the $E_{\text{CM}}=2709\mathrm{keV}$ resonance persists. Resonance strengths and energies were determined for five low-energy resonances which had not been studied previously, and their strengths were determined to be significantly weaker than those of previously measured resonances.

Conclusions: The five previously unmeasured resonances were found not to contribute significantly to the total thermonuclear reaction rate. A median total thermonuclear reaction rate calculated using data from the present work along with existing literature values using the STARLIB rate calculator agrees with the NON-SMOKER statistical model calculation as well as the REACLIB and STARLIB library rates at explosive and nonexplosive oxygen-burning temperatures ($T=3–4\mathrm{GK}$ and $T=1.5–2.7\mathrm{GK}$, respectively).

Starting from solutions of the lightly bound Skyrme model, we construct many new Skyrmion solutions of the standard Skyrme model with tetrahedral or octahedral symmetry. These solutions are closely related to weight diagrams of the group SU(4), which enables us to systematically derive some geometric and energetic properties of the Skyrmions, up to baryon number 85. We discuss the rigid-body quantization of these Skyrmions and compare the results with properties of a selection of observed nuclei.

The ground-state deformations of heavy nuclei are explored with the microscopic-macroscopic approach using the single-particle Woods-Saxon potential of the quasiparticle-phonon model. The calculations of the energies of low-lying nonrotational states take into account the residual pairing and phonon-quasiparticle interactions. The spectra of these states are presented for the $N=147–161$ isotones. The sensitivity of the calculated results to the parameters of the model is studied. A rather good description of the available experimental data is demonstrated.

Charged-current (anti)neutrino-${}^{40}\mathrm{Ar}$ cross sections for astrophysical neutrinos have been calculated. The initial and final nuclear states were calculated using the nuclear shell model. The folded solar-neutrino scattering cross section was found to be $1.78\left(23\right)\times {10}^{-42}{\mathrm{cm}}^2$, which is higher than what the previous papers have reported. The contributions from the $1^{-}$ and $2^{-}$ multipoles were found to be significant at supernova-neutrino energies, confirming the random-phase approximation (RPA) result of a previous study. The effects of neutrino flavor conversions in dense stellar matter (matter oscillations) were found to enhance the neutrino-scattering cross sections significantly for both the normal and inverted mass hierarchies. For the antineutrino scattering, only a small difference between the nonoscillating and inverted-hierarchy cross sections was found, while the normal-hierarchy cross section was 2–3 times larger than that of the nonoscillating cross section, depending on the adopted parametrization of the Fermi-Dirac distribution. This property of the supernova-antineutrino signal could probably be used to distinguish between the two hierarchies in megaton LAr detectors.

Based on the newly updated version of the ultrarelativistic quantum molecular dynamics (UrQMD) model, the pion potentials obtained from the in-medium dispersion relation of the $\mathrm{\Delta }$-hole model and from the modified phenomenological approach are further introduced. Both the rapidity $y_0$ and transverse-velocity $u_{t0}$ dependence of directed $v_1$ and elliptic $v_2$ flows of ${\pi }^{+}$ and ${\pi }^{-}$ charged mesons produced from Au+Au collisions at two beam energies of 1.0 and 1.5 GeV/nucleon and within a large centrality region of $0<b_0<0.55$ are scanned. Calculations with pion potentials as well as without considering the pion potential are compared to the newly experimental data released by the FOPI Collaboration at GSI Helmholtzzentrum für Schwerionenforschung. It is found that the directed flow is more sensitive to the pion potential than the elliptic one, and the attractive pion potential from the phenomenological B mode of the phenomenological approach is too strong to describe the flow data and can be safely ruled out. The relatively weak pion potential from the $\mathrm{\Delta }$-hole model can supply a good description for the FOPI data of both flows as functions of both centrality and rapidity. A two-peak structure occurs in the transverse-velocity-dependent directed flow but the elliptic flow drops monotonously with increasing $u_{t0}$. Finally, both $v_1$ and $v_2$ flows with large $u_{t0}$ from semicentral heavy-ion collisions can be taken as sensitive probes for the pion potential.

We study the transfer of angular momentum in high energy nuclear collisions from the colliding nuclei to the region around midrapidity, using the classical approximation of the color glass condensate (CGC) picture. We find that the angular momentum shortly after the collision (up to times $\sim 1/Q_s$, where $Q_s$ is the saturation scale) is carried by the “$\beta$-type” flow of the initial classical gluon field, introduced by some of us earlier. ${\beta }^i\sim {\mu }_1{\mathbf{\nabla }}^i{\mu }_2-{\mu }_2{\mathbf{\nabla }}^i{\mu }_1\left(i=1,2\right)$ describes the rapidity-odd transverse energy flow and emerges from Gauss's law for gluon fields. Here ${\mu }_1$ and ${\mu }_2$ are the averaged color charge fluctuation densities in the two nuclei, respectively. Interestingly, strong coupling calculations using anti-de Sitter/conformal field theory (AdS/CFT) techniques also find an energy flow term featuring this particular combination of nuclear densities. In classical CGC the order of magnitude of the initial angular momentum per rapidity in the reaction plane, at a time $1/Q_s$, is $|d{L}_2/d\eta |\approx R_A{Q}_s^{-3}{\overline{\varepsilon }}_0/2$ at midrapidity, where $R_A$ is the nuclear radius, and ${\overline{\varepsilon }}_0$ is the average initial energy density. This result emerges as a cancellation between a vortex of energy flow in the reaction plane aligned with the total angular momentum, and energy shear flow opposed to it. We discuss in detail the process of matching classical Yang-Mills results to fluid dynamics. We will argue that dissipative corrections should not be discarded to ensure that macroscopic conservation laws, e.g., for angular momentum, hold. Viscous fluid dynamics tends to dissipate the shear flow contribution that carries angular momentum in boost-invariant fluid systems. This leads to small residual angular momentum around midrapidity at late times for collisions at high energies.