We propose a numerical method to determine the optimal collective reaction path for a nucleus-nucleus collision, based on the adiabatic self-consistent collective coordinate (ASCC) method. We use an iterative method, combining the imaginary-time evolution and the finite amplitude method, for the solution of the ASCC coupled equations. It is applied to the simplest case, $\alpha -\alpha$ scattering. We determine the collective path, the potential, and the inertial mass. The results are compared with other methods, such as the constrained Hartree-Fock method, Inglis's cranking formula, and the adiabatic time-dependent Hartree-Fock (ATDHF) method.

Angular-momentum or parity-dependent nonlocal optical potentials for nucleon-${}^{16}\mathrm{O}$ scattering able to fit differential cross-section data over the whole angular regime are developed and applied to the description of deuteron-${}^{16}\mathrm{O}$ scattering in the framework of three-body Faddeev-type equations for transition operators. Differential cross sections and deuteron analyzing powers for elastic scattering and ${}^{16}\mathrm{O}(d,p){}^{17}\mathrm{O}$ transfer reactions are calculated by using a number of local and nonlocal optical potentials and compared with experimental data. Angular-momentum or parity-dependence of the optical potential turns out to be quite irrelevant in the considered three-body reactions whereas nonlocality is essential for a successful description of the differential cross-section data, especially in transfer reactions.

The microscopic description of heavy-ion reactions at low beam energies is achieved within hadronic transport approaches. In this article a new approach called “Simulating Many Accelerated Strongly interacting Hadrons” (SMASH) is introduced and applied to study the production of nonstrange particles in heavy-ion reactions at $E_{\mathrm{kin}}=0.4A–2A$ GeV. First, the model is described including details about the collision criterion, the initial conditions and the resonance formation and decays. To validate the approach, equilibrium properties such as detailed balance are presented and the results are compared to experimental data for elementary cross sections. Finally results for pion and proton production in $\text{C}+\text{C}$ and $\text{Au}+\text{Au}$ collisions is confronted with data from the high-acceptance dielectron spectrometer (HADES) and FOPI. Predictions for particle production in $\pi +A$ collisions are made.

The ratios of off-diagonal and diagonal susceptibilities of conserved charges are studied using a hadron resonance gas (HRG) model with an emphasis towards providing a proper baseline for comparison to the corresponding future experimental measurements. We have studied the effect of kinematic acceptances, transverse momentum ($p_T$), and pseudorapidity ($\eta$), and different charged states on the ratios of the calculated susceptibilities. We find that the effect of $p_T$ and $\eta$ acceptance on the ratio of the susceptibilities is small relative to their dependence on the beam energy or the charged states of the used particles. We also present a HRG based calculation for various combinations of cumulant ratios of protons and pions, recently proposed as robust observables (with no theoretical uncertainties) for critical point search in the experiments. These results which increase as a function of collision energy will provide a better baseline for noncritical point physics compared to Poisson expectation.

The polarization of $\mathrm{\Lambda }$ hyperons from relativistic flow vorticity is studied in peripheral heavy ion reactions at FAIR and NICA energies, just above the threshold of the transition to the quark-gluon plasma. Previous calculations at higher energies with larger initial angular momentum, predicted significant $\mathrm{\Lambda }$ polarization based on the classical vorticity term in the polarization, while relativistic modifications decreased the polarization and changed its structure in the momentum space. At the lower energies studied here, we see the same effect namely that the relativistic modifications decrease the polarization arising from the initial shear flow vorticity.

Ab initio calculations provide direct access to the properties of pure neutron systems that are challenging to study experimentally. In addition to their importance for fundamental physics, their properties are required as input for effective field theories of the strong interaction. In this work, we perform auxiliary-field diffusion Monte Carlo calculations of the ground state and first excited state of two neutrons in a finite box, considering a simple contact potential as well as chiral effective field theory interactions. We compare the results against exact diagonalizations and present a detailed analysis of the finite-volume effects, whose understanding is crucial for determining observables from the calculated energies. Using the Lüscher formula, we extract the low-energy $S$-wave scattering parameters from ground- and excited-state energies for different box sizes.

The dynamics of the nuclear fragmentations and the charge exchange reactions in pion-nucleus collisions near the $\mathrm{\Delta }$(1232) resonance energies has been investigated within the Lanzhou quantum molecular dynamics transport model. An isospin-, momentum-, and density-dependent pion-nucleon potential is implemented in the model, which influences the pion dynamics, in particular the kinetic energy spectra, but weakly impacts the fragmentation mechanism. The absorption process in pion-nucleon collisions to form the $\mathrm{\Delta }$(1232) resonance dominates the heating mechanism of the target nucleus. The excitation energy transferred to the target nucleus increases with the pion kinetic energy and is similar for both ${\pi }^{-}-$ and ${\pi }^{+}\text{-induced}$ reactions. The magnitude of fragmentation of the target nucleus weakly depends on the pion energy. The isospin ratio in the pion double-charge exchange is influenced by the isospin ingredient of target nucleus.

The radial basis function (RBF) approach has been used to improve the mass predictions of nuclear models. However, systematic deviations were found between the improved masses and the experimental data for nuclei with four different odd-even parities of $(Z,N)$, i.e., (even $Z$, even $N$), (even $Z$, odd $N$), (odd $Z$, even $N$), and (odd $Z$, odd $N$). In this work, we show that such deviations can be eliminated to a large extent by separately training the RBF for the groups of parities, resulting in a further improved predictive power of nuclear mass models and in particular single-nucleon separation energies. With this new RBF approach, the root-mean-square mass deviation for the latest version of the Weizsäcker-Skyrme model WS4, falls to 135 keV with respect to known data. This is approaching the chaos-related unpredictability limit ($\sim 100$ keV).

Heavy even-even nuclei exhibit low-energy collective excitations that are separated in scale from the microscopic (fermion) degrees of freedom. This separation of scale allows us to approach nuclear vibrations within an effective field theory (EFT). In odd-mass nuclei collective and single-particle properties compete at low energies, and this makes their description more challenging. In this article we describe spherical odd-mass nuclei with ground-state spin $I=\frac{1}{2}$ by means of an EFT that couples a fermion to the collective degrees of freedom of an even-even core. The EFT relates observables such as energy levels, electric quadrupole transition strengths, and magnetic dipole moments of the odd-mass nucleus to those of its even-even neighbor and allows us to quantify theoretical uncertainties. For isotopes of rhodium and silver the theoretical description is consistent with data within experimental and theoretical uncertainties. Several testable predictions are made.

The neutron matter equation of state is calculated from two-neutron forces up to fifth order of the chiral expansion, and the order-by-order convergence of the predictions is investigated. Based on these equations of state, the binding energies and the neutron and proton density distributions in ${}^{208}\mathrm{Pb}$ and ${}^{48}\mathrm{Ca}$ are derived, with particular attention paid to the neutron skins, the focal point of this paper. Anticipating future experiments which will provide reliable information on the weak charge density in nuclei, the theoretical uncertainties and the possibility of constraining the size of few-neutron forces in neutron matter are discussed.

The proton transfer ${}^7\mathrm{Be}\left(d,n\right){}^8\mathrm{B}$ reaction at the energy of 4.5 MeV (center of mass) has been analyzed within the modified distorted-wave Born approximation. New estimates and their uncertainties are obtained for values of the asymptotic normalization coefficients for $p+{}^7\mathrm{Be}\to {}^8\mathrm{B}$, the astrophysical $S_{17}\left(0\right)$ factor, and the $s$-wave $p+{}^7\mathrm{Be}$ scattering lengths.

The energy dependence of the longitudinal asymmetry $\left(A_L\right)$ and the spin rotation of the proton on the deuterium target in the $\vec{p}d$ scattering are presented using the pionless effective field theory formalism. The strong, weak, and Coulomb interactions have been introduced in the $\vec{p}d$ scattering. We have shown that in the presence of Coulomb interaction, the parity-conserving (PC) and the parity-violating (PV) sectors are modified. The PV two-body transitions diagrams have been evaluated with the inclusion of Coulomb interaction and consequently the PV observables are enhanced. The leading-order values of the $A_L$ and the spin rotation of the proton on the deuterium target are calculated at the proton laboratory energies above 0.7 MeV, in order to calculate the Coulomb effect perturbatively, up to 3 MeV where typical momenta is $Q\ll m_{\pi }$. With the lack of experimental data for the low-energy coupling constants (LECs), we have used two estimated sets for the five independent (PV) LECs of the weak $NN$ PV Lagrangian. The order of magnitude, of the PV observables with these two sets, is found to be ${10}^{-6}$ to ${10}^{-7}$ which indicates that the expected order is achieved in this energy range. The cutoff independent results support the validity of our approach.

We study the proton radiative capture by a deuteron with the pionless effective field theory [EFT($\pi /$)] formalism. The calculation of the $pd\to {}^3\mathrm{He}\gamma$ amplitude is considered for the incoming doublet and quartet channels leading to the formation of a ${}^3\mathrm{He}$. The strong and Coulomb scattering amplitudes for the proton-deuteron ($pd$) scattering are included in this study. In this calculation, the properly normalized ${}^3\mathrm{He}$ wave function has been used at each order. We evaluate both $M1$ and $E1$ transitions in the $pd\to {}^3\mathrm{He}\gamma$ process up to NLO. We calculate the total cross section for the $pd\to {}^3\mathrm{He}\gamma$ process based on the cluster-configuration space and compare it with the experimental data. The cross section results are presented for the incoming proton with the energy $0.5\le E\le 3$ MeV where the lower and upper limits are chosen for the treatment of Coulomb effects perturbatively and the EFT($\pi /$) breakdown scale, respectively. No three-body force is needed to renormalize observables up to NLO other than those we have introduced in the $pd$ scattering amplitudes.

Background: $\gamma$ strength functions (GSFs) and level densities (LDs) are essential ingredients of statistical nuclear reaction theory with many applications in astrophysics, reactor design, and waste transmutation.

Purpose: The aim of the present work is a test of systematic parametrizations of the GSF recommended by the RIPL-3 database for the case of ${}^{208}\text{Pb}$. The upward GSF and LD in ${}^{208}\text{Pb}$ are compared to $\gamma$ decay data from an Oslo-type experiment to examine the validity of the Brink-Axel (BA) hypothesis.

Methods: The $E1$ and M1 parts of the total GSF are determined from high-resolution forward angle inelastic proton scattering data taken at 295 MeV at the Research Center for Nuclear Physics (RCNP), Osaka, Japan. The total LD in ${}^{208}\text{Pb}$ is derived from the $1^{-}$ LD extracted with a fluctuation analysis in the energy region of the isovector giant dipole resonance.

Results: The $E1$ GSF is compared to parametrizations recommended by the RIPL-3 database showing systematic deficiencies of all models in the energy region around neutron threshold. The new data for the poorly known spin-flip $M1$ resonance call for a substantial revision of the model suggested in RIPL-3. The total GSF derived from the present data is larger in the PDR energy region than the Oslo data but the strong fluctuations due to the low LD resulting from the double shell closure of ${}^{208}\text{Pb}$ prevent a conclusion on a possible violation of the BA hypothesis. Using the parameters suggested by RIPL-3 for a description of the LD in ${}^{208}\text{Pb}$ with the back-shifted Fermi gas model, remarkable agreement between the two experiments spanning a wide excitation energy range is obtained.

Conclusions: Systematic parametrizations of the $E1$ and $M1$ GSF parts need to be reconsidered at low excitation energies. The good agreement of the LD provides an independent confirmation of the approach underlying the decomposition of GSF and LD in Oslo-type experiments.

There are excellent opportunities to produce excited heavy hyperresidues in relativistic hadron and peripheral heavy-ion collisions. We investigate the disintegration of such residues into hypernuclei via evaporation of baryons and light clusters and their fission. Previously these processes were well known for normal nuclei as the decay channels at low excitation energies. We have generalized these models for the case of hypermatter. In this way we make extension of nuclear reaction studies at low temperature into the strange sector. We demonstrate how the new decay channels can be integrated in the whole disintegration process. Their importance for mass and isotope distributions of produced hyperfragments is emphasized. New and exotic isotopes obtained within these processes may provide a unique opportunity for investigating hyperon interaction in nuclear matter.

It is shown that large chemical potential leads to the significant increase of multiplicity fluctuations for bosons, and makes the fluctuations infinite in the case of Bose-Einstein condensation. It allows us to distinguish between the models that explain the anomalous proton to pion ratio and the low transverse momentum enhancement of pion spectra in Pb+Pb collisions at the Large Hadron Collider within chemical equilibrium or nonequilibrium models. The effects of resonance decays, finite size of the system, requirements to the event statistics, different momentum cuts, and limited detector acceptance are considered. The obtained results show the possibility to observe a substantial increase of the normalized kurtosis for positively or negatively charged pions in the case of nonequilibrium or partial pion condensation using currently measured data.