Background: In recent decades, reactions involving weakly bound projectiles have been investigated by several research groups working in the nuclear physics field. Despite the relative success of a few theoretical models in addressing some reaction outcomes, many puzzling questions remain. A relatively large number of reactions with weakly bound nuclei have been systematically investigated at the Open Laboratory of Nuclear Physics of the University of São Paulo. The present data set is analyzed through coupled reaction channels calculations in the context of the double-folding São Paulo potential.

Purpose: The main goal of the present paper is to investigate nuclear reaction mechanisms for systems involving weakly bound projectiles.

Method: Angular distributions for several nuclear reaction processes were measured for the ${}^{6,7}\mathrm{Li}+{}^{124}\mathrm{Sn}$ systems at energies around the Coulomb barrier. Fusion data obtained in other works for both systems at energies below and above the barrier are also analyzed in the present paper.

Results: Angular distributions of elastic and inelastic scattering, as well as transfer, were obtained at the 30B scattering chamber of the Open Laboratory of Nuclear Physics of the University of São Paulo. The effect of the couplings to some nonelastic states on the angular distributions is discussed throughout the paper. Fusion cross sections were also analyzed using the coupled reaction channels approach. A strong absorptive imaginary potential is necessary to explain the measured angular distributions and fusion excitation functions.

Conclusion: The theoretical calculations within the coupled reaction channels formalism provide an overall good agreement with the corresponding elastic, inelastic, transfer, and fusion data.

Excited states of ${}^{92}\mathrm{Nb}$ were investigated using the reactions ${}^{82}\mathrm{Se}({}^{14}\mathrm{N}, 4n)$ and ${}^{89}\mathrm{Y}({}^6\mathrm{Li}, 1p2n)$. Based on these experimental results, the level scheme was extended abundantly. The structures of both the positive and negative parity states have been compared with shell model calculations using the SNET interaction. Potential energy surface calculation using the configuration-constrained method was performed to study a rotational-like band in ${}^{92}\mathrm{Nb}$, and possible configuration of the band head has been discussed. The calculation indicates that it may be an oblate collective rotational band.

The momentum dependence of the nucleon mean-field potential in a wide momentum range can be an important factor to determine the $\mathrm{\Delta }$ resonance and pion production in intermediate-energy heavy-ion collisions. In particular, in neutron-rich systems such as ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ collisions, we need to carefully treat the momentum dependence because the neutron and proton potentials can have different momentum dependence, as characterized at low momenta by effective masses. In the present work, we rigorously calculate the collision terms of $NN\leftrightarrow N\mathrm{\Delta }$ and $\mathrm{\Delta }\leftrightarrow N\pi$ processes with the precise conservation of energy and momentum under the presence of momentum-dependent potentials for the initial and final particles of the process. The potentials affect not only the threshold condition for the process but also the cross section in general as a function of the momenta of the initial particles, which is treated in a natural way in the present work. Calculations are performed by combining the nucleon dynamics obtained by the antisymmetrized molecular dynamics (AMD) model with a newly developed transport code which we call sJAM. The calculated results for central ${}^{132}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ collisions at 270 MeV/nucleon clearly show that the momentum dependence of the neutron and proton potentials has a significant impact on the $NN\to N\mathrm{\Delta }$ process, and this information is strongly reflected in the charged pion ratio (${\pi }^{-}/{\pi }^{+}$). We also investigate the effects of the high-density symmetry energy and the isovector part of the potential of $\mathrm{\Delta }$ resonances on pion production, which we find are relatively small compared to the effect of the momentum dependence of the neutron and proton potentials.

In this paper we investigate the production of charmonium states in two- and three-photon fusion processes in nucleus-nucleus collisions at the CERN Large Hadron Collider energies. Our results indicate that the experimental study of these processes is feasible and can be used to constrain the theoretical decay widths and give information on the non $c\text{−}\overline{c}$ components of these states.

Based on the back-propagation neural networks and density functional theory, a supervised learning is performed firstly to generate the nuclear charge density distributions. The charge density is further calibrated to the experimental charge radii by a composite loss function. It is found that, when the parity, pairing, and shell effects are taken into account, about $96\%$ of the nuclei in the validation set fall within 2 standard deviations of the predicted charge radii. Moreover, the kink in charge radii on Hg isotopes has been successfully reproduced. The calibrated charge density is then mapped to the matter density and further mapped to the binding energies according to the Hohenberg-Kohn theorem. It provides an improved description of some nuclei in both binding energies and charge radii. Moreover, the anomalous overbinding in ${}^{48}\mathrm{Ca}$ implies that the segmental calibrations by neural networks for beyond-mean-field effects deserve further discussion.

Background: Even-even isotopes of Mo $(Z=42)$ and Ru $(Z=44)$ are nuclei close to the subshell closure at $Z=40$, where shape coexistence plays a significant role. As a result, their spectroscopic properties are expected to resemble those of Sr $(Z=38)$ and Zr $(Z=40)$. Exploring the evolution of these properties as they move away from the subshell closure is of great interest.

Purpose: The purpose of this study is to reproduce the spectroscopic properties of even-even ${}_{\phantom{961\text{–}}42}{}^{96–110}\mathrm{Mo}$ and ${}_{\phantom{961\text{–}}44}{}^{98–114}\mathrm{Ru}$ isotopes and to determine the influence of shape coexistence.

Method: We employed the interacting boson model with configuration mixing as the framework to calculate all the observables for Mo and Ru isotopes. We considered two types of configurations: 0-particle–0-hole and 2-particle–2-hole excitations. The model parameters were determined using a least-squares fitting to match the excitation energies and the $B\left(E2\right)$ transition rates.

Results: We obtained the excitation energies, $B\left(E2\right)$ values, two-neutron separation energies, nuclear radii, and isotope shifts for the entire chain of isotopes. Our theoretical results show good agreement with experimental data. Furthermore, we conducted a detailed analysis of the wave functions and obtained the mean-field energy surfaces and the nuclear deformation parameter, $\beta$, for all considered isotopes.

Conclusions: Our findings reveal that shape coexistence plays a significant role in Mo isotopes, with the crossing of intruder and regular configurations occurring at neutron number 60 $(A=102)$, which induces a quantum phase transition. In contrast, in Ru isotopes, the intruder states have minimal influence, remaining at higher energies. However, at neutron number 60, also a quantum phase transition occurs in Ru isotopes.

The impact of different diquark fragmentation mechanisms on proton, ${\pi }^{\pm }$, and $K^{\pm }$ spectra in $20\%$ central ${}^7\mathrm{Be}+{}^9\mathrm{Be}$ collisions has been investigated at the CERN Super Proton Synchrotron (SPS) energies using the Heavy Ion Jet Interaction Generator (hijing) code. The advanced popcorn (AP) string model of pythia 6.4 was employed, and two popcorn scenarios for diquark fragmentation were considered: The simple diquark model and the AP model. The AP mechanism allows for the implementation of beam remnant diquark fragmentation (BRDF), which occurs when a quark is expelled from a proton beam. The AP model provides two possible channels for baryon production from BRDF: The baryon-antibaryon $\left(B\overline{B}\right)$ configuration, as well as configurations such as $BM\overline{B}$ and $BMM\overline{B}$. In the diquark model, a $B\overline{B}$ is always produced from the diquark-antidiquark $(qq-\overline{q}\overline{q})$ pair production between the original $(q_0-{\overline{q}}_0)$ jet pair. It is shown that the diquark model is more suitable for explaining the proton density at midrapidity compared to the default AP approach, which exhibits an unusual arrangement of peaks and dips in proton spectra at midrapidity. However, the hijing/diquark calculations are not consistent with proton diffraction peaks and the production of new particles. On the other hand, the BRDF effects implemented in hijing/AP are found to be more suited for the description of proton stopping observables in central $\mathrm{Be}+\mathrm{Be}$ collisions, while still producing the correct ${\pi }^{\pm }$ and $K^{\pm }$ $dN/dy$ and $p_T$ spectra at midrapidity for the entire range of SPS energies.

We present an efficient method to prepare states of a many-body system on quantum hardware, first isolating individual quantum numbers and then using time evolution to isolate the energy. Our method in its simplest form requires only one additional auxiliary qubit. The total time evolved for an accurate solution is proportional to the ratio of the spectrum range of the trial state to the gap to the lowest excited state, a substantial improvement over other projection algorithms, and the accuracy increases exponentially with the time evolved. Isolating the quantum numbers is efficient because of the known eigenvalues, and increases the gap thus shortening the propagation time required. The success rate of the algorithm, or the probability of producing the desired state, is a simple function of measurement times and phases and is dominated by the square overlap of the original state to the desired state. We present examples from the nuclear shell model and the Heisenberg model. We compare this algorithm to previous algorithms for short evolution times and discuss potential further improvements.

We derive explicit expressions for the Landau sum rules for the case of the most general spin-dependent quasiparticle interaction including all possible tensor interactions. For pure neutron matter, we investigate the convergence of the sum rules at different orders of approximation. Employing modern nuclear Hamiltonians based on chiral effective field theory, we find that the inclusion of noncentral interactions improves the convergence of the sum rules only for low densities $(n\lesssim 0.1 {\mathrm{fm}}^{-3})$. Around nuclear matter saturation density, we find that even ostensibly perturbative nuclear interactions violate the sum rules considerably. By artificially weakening the strength of the nuclear Hamiltonian, the convergence can be improved.

The entanglement properties of neutron-proton scattering are investigated using a measure that counts the number of entangled pairs produced by the action of a scattering operator on a given initial neutron-proton state. All phase shifts relevant for scattering at laboratory energies up to 350 MeV are used. Entanglement is found to depend strongly on the initial state. Entanglement is maximized in very low energy scattering if the initial spin state is $|\uparrow \downarrow \rangle$, but not if the initial state is $|\uparrow \uparrow \rangle$. At such energies the Hamiltonian obeys Wigner SU(4) symmetry, and an entanglement maximum is a sign of that symmetry. At higher energies the angular dependence of entanglement is strong and the entanglement is large for many scattering angles. The tensor force is shown to play a significant role in producing entanglement at laboratory kinetic energies greater than about 50 MeV.

The empirical spectra and $E2$ decay rates in ${}^{110,112,114,116}\mathrm{Cd}$ are shown to be consistent with a vibrational interpretation for low-lying normal states, coexisting with a single deformed $\gamma$-soft band of intruder states. The observed deviations from this paradigm show up in particular nonyrast states, which are properly described by a Hamiltonian with U(5) partial dynamical symmetry. The latter is characterized by a good (broken) symmetry in most (in selected) normal states, weakly coupled to intruder states.

Background: The pairing correlation in weakly bound nuclei causes a mixing among bound and unbound configurations. A remarkable consequence is the emergence of the quasiparticle resonance, which has been predicted with the coordinate space Hartree-Fock-Bogoliubov (HFB) theory, but not yet observed experimentally.

Purpose: We discuss possible observation of quasiparticle resonances in decay spectrum of unbound nuclei near the neutron drip-line. We deal with an example of unbound nucleus ${}^{21}\mathrm{C}$ which disintegrates to ${}^{20}\mathrm{C}$ and a neutron.

Method: We describe a scattering state consisting of ${}^{20}\mathrm{C}$ and a neutron in the framework of the HFB formalism. We assume that a nucleon knockout reaction produces a doorway state of the decay, and we evaluate the decay spectrum by taking an overlap of the doorway state and the scattering state of ${}^{20}\mathrm{C}+n$. A numerical calculation was performed with the Woods-Saxon potential and a density-dependent effective pairing interaction.

Results: We show that the quasiparticle resonance appears as low-lying peaks in the decay spectrum of ${}^{21}\mathrm{C}$. They originate from the weakly bound single-neutron orbits $2s_{1/2}$ and $1d_{5/2}$, but emerge as unbound resonant quasiparticle states under the influence of the neutron pairing correlation. The resonance energy and the width of the calculated quasiparticle resonances are consistent with an experimental observation whereas they are sensitive to the neutron pairing correlation.

Conclusion: The results suggest that nucleon knockout reactions populating the unbound nucleus ${}^{21}\mathrm{C}$ provide realistic opportunity of experimentally observing the quasiparticle resonance and of disclosing the pairing correlation in neutron-rich nuclei.

Dispersion corrections to elastic electron scattering from ${}^{208}\mathrm{Pb}$ at energies up to 150 MeV are estimated within the second-order Born approximation. All strong transient nuclear excited states with angular momentum up to $L=3$ and natural parity are taken into consideration. It is found that at small scattering angles the high-lying $L=1$ isovector states provide the dominant contribution to the dispersive change of the differential cross section and of the beam-normal spin asymmetry. At the back-most angles these changes are considerably smaller and are basically due to the isoscalar $L=2$ and, to a lesser extent, $L=3$ states. In comparison with the findings for ${}^{12}\mathrm{C}$, the dispersive cross-section modifications for ${}^{208}\mathrm{Pb}$ are significantly larger, while the spin-asymmetry changes are much smaller at all angles. The latter originates from the destructive interference of the multipole contributions in ${}^{208}\mathrm{Pb}$ that switch sign when proceeding from $L$ to $L+1$. This mechanism might be the origin of the small beam-normal spin asymmetries recently measured in ${}^{208}\mathrm{Pb}$ at much larger energies.

A simple model for medium modification of the jet function can be used to extract the jet energy loss distribution through a parameterized form. We carry out a comprehensive Bayesian analysis of the world data on single inclusive jet spectra in heavy-ion collisions at both BNL Relativistic Heavy Ion Collider and CERN Large Hadron Collider energies. We extract the average jet energy loss $\langle \mathrm{\Delta }E\rangle$ as a function of jet transverse momentum $p_T$ for each collision system and centrality independently. Assuming jet energy loss is proportional to the initial parton density $\rho \sim d{N}_{\mathrm{ch}}/d\eta /\pi R_{\mathrm{eff}}^2$ as estimated from the pseudorapidity density of charged hadron multiplicity $d{N}_{\mathrm{ch}}/d\eta$ and the effective system size $R_{\mathrm{eff}}\sim N_{\mathrm{part}}^{1/3}$ given by the number of participant nucleons $N_{\mathrm{part}}$, the scaled average jet energy loss $\langle \mathrm{\Delta }E\rangle /\rho \sim R_{\mathrm{eff}}^{0.59}{p}_T^{0.13}ln{p}_T$ for jet cone-size $R=0.4$ is found to have a momentum dependence that is slightly stronger than a logarithmic form while the system size or length dependence is slower than a linear one. The fluctuation of jet energy loss is, however, independent of the initial parton density or the system size.

The analyses of NICER data imply $R_{2.0M_{\odot }}=12.{41}_{-1.10}^{+1.00}\mathrm{km}$ and $R_{1.4M_{\odot }}=12.{56}_{-1.07}^{+1.00}\mathrm{km}$, indicating the lack of significant variation of the radii from $1.4M_{\odot }$ to $2.0M_{\odot }$. This feature cannot be reproduced by hadronic matter due to the softening of equation of state (EoS) by hyperon mixing, indicating the possible existence of quark phases in neutron-star interiors. Two models are used for quark phases: In the quark-hadron transition (QHT) model, quark deconfinement phase transitions from a hadronic-matter EoS are taken into account so as to give reasonable mass-radius ($MR$) curves by adjusting the quark-quark repulsions and the density dependence of the effective quark mass. In the quarkyonic model, the degrees of freedom inside the Fermi sea are treated as quarks, and neutrons exist at the surface of the Fermi sea, where $MR$ curves are controlled mainly by the thickness of neutron Fermi layer. The QHT and quarkyonic EoSs can be adjusted so as to reproduce radii, tidal deformabilities, pressure, and central densities inferred from the NICER analysis better than the nucleonic matter EoS, demonstrating the clear impacts of quark phases. Then, the maximum mass for the quakyonic-matter EoS is considerably larger than that for the QHT-matter EoS.

Within an isospin- and momentum-dependent Boltzmann-Uehling-Uhlenbeck transport model, we investigate the hard photons emission from neutron-proton bremsstrahlung in the reaction system of ${}^{208}\mathrm{Pb}+{}^{208}\mathrm{Pb}$ around Fermi energy. Effects of neutron skins in coordinate ($r$) space and proton skins in momentum ($k$) space on the time evolution, the angular distribution, and the transverse momentum spectra of hard photons with different energies are studied. It is shown that the emission of direct hard photons is sensitive to the neutron skin, which has larger effects for more energetic hard photons. Meanwhile, we find that the proton skins have an important influence on the emission of direct hard photons, and its effect is actually even larger than that of neutron skins. It needs to take the effect of proton skins into account when we determine the size of neutron skins by comparing transport mode predictions of hard photons with the corresponding experimental measurements.

The primordial elemental abundance composition of the first stars leads to questions about their modes of energy production and nucleosynthesis. The formation of ${}^{12}\mathrm{C}$ has been thought to occur primarily through the $3\alpha$ process, however, alternative reaction chains may contribute significantly, such as ${}^7\mathrm{Li}(\alpha ,\gamma ){}^{11}\mathrm{B}(\alpha ,n){}^{14}\mathrm{N}$. This reaction sequence cannot only bypass the mass $A=8$ stability gap, but could also be a source of neutrons in the first star environment. However, the efficiency of this reaction chain depends on the possible enhancement of its low energy cross section by $\alpha$-cluster resonances near the reaction threshold. A new study of the reaction ${}^{11}\mathrm{B}(\alpha ,n)$ ${}^{14}\mathrm{N}$ has been undertaken at the CASPAR underground facility at beam energies from $300\text{–}700\mathrm{keV}$. A $4\pi$ neutron detector in combination with pulse shape discrimination at low background conditions resulted in the ability to probe energies lower than previously measured. Resonance strengths were determined for both the resonance at a laboratory energy of $411\mathrm{keV}$, which was measured for the second time, and for a new resonance at $337\mathrm{keV}$ that has been measured for the first time. This resonance, found to be significantly weaker than previous estimates, dominates the reaction rate at lower temperatures ($T<0.2\mathrm{KG}$) and reduces the reaction rate in first star environments.

We investigate the question of the nature of compact stars, considering they may be neutron stars or hybrid stars containing a quark core, within the present constraints given by gravitational waves, radio-astronomy, x-ray emissions from millisecond pulsars and nuclear physics. A Bayesian framework is used to combine together all these constraints and to predict tidal deformabilities and radii for a 1.4 ${\mathrm{M}}_{\odot }$ compact star. We find that present gravitation wave and radioastronomy data favor stiff nucleonic equation of state (EoS) compatible with nuclear physics and that GW170817 waveform is best described for binary hybrid stars. Binary neutron stars with soft EoS could however not be totally excluded. In all cases, these data favor stiff quark matter, independently of the nuclear EoS, with a low value for the transition density ($n_{\mathrm{tr}}\in [0.18,0.35]{\mathrm{fm}}^{-3}$). Combining these results with constraints from x-ray observation supports the existence $1.4{\mathrm{M}}_{\odot }$ mass hybrid star, with a radius predicted to be about $R_{1.4}=12.22\left(45\right)\mathrm{km}$.