Inclusive breakup is an important reaction mechanism of reactions induced by weakly bound nuclei. The Ichimura, Austern, and Vincent (IAV) model is widely used to analyze inclusive breakup processes and is based on a distorted wave Born approximation (DWBA). However, the validity of the DWBA form for inclusive breakup requires further exploration. In this study, we present a derivation of the IAV model, using the continuum-discretized coupled-channels (CDCC) wave function, and apply it to the $d+{}^{93}\mathrm{Nb}$ reaction. We examine the differences between the CDCC-IAV and DWBA-IAV models by artificially modifying the binding energy of the deuteron using two distinct types of optical potential. Our findings indicate that the CDCC method potentially provides a more fundamental description of the $d+A$ interaction and may provide a more realistic description of the interior part of the wave function. This study offers significant potential in increasing the precision and dependability of weakly bound nuclei inclusive breakup process estimation within a fully quantum mechanical model.

To reconstruct the impact parameter distributions from the selected events sample or centrality, which is defined by two observables, at intermediate energy heavy ion collisions, we extend the approach proposed by Das et al. [Phys. Rev. C 97, 014905 (2018)], Rogly et al. [Phys. Rev. C 98, 024902 (2018)], and Frankland et al. [Phys. Rev. C 104, 034609 (2021)]. Based on deep investigations of the fluctuation mechanism, we found that the intrinsic fluctuations are mainly generated in the microscopic stochasticity of initialization and nucleon-nucleon collisions in the nonequilibrium process of heavy ion collisions, and this leads the observables to fluctuate with respect to impact parameter in a Gaussian form. In this work, the multiplicity of the charged particles and the total transverse momentum of the light charged particles are used simultaneously to model-independently reconstruct the impact parameter distributions for selected events or centrality based on the Bayesian method. For sorting the centrality with two observables, we propose to use the $K$-means clustering method (an unsupervised machine learning algorithm), which can automatically sort events when the class number is given. Furthermore, the reconstructed impact parameter distributions from data of the two observables can be used to learn the correlation between multiplicity and transverse momentum at different centralities, which may be useful for understanding the fragmentation mechanism.

We train a deep convolutional neural network to predict hydrodynamic results for flow coefficients, average transverse momenta, and charged particle multiplicities in ultrarelativistic heavy-ion collisions from the initial energy density profiles. We show that the neural network can be trained accurately enough so that it can reliably predict the hydrodynamic results for the flow coefficients and, remarkably, also their correlations like normalized symmetric cumulants, mixed harmonic cumulants, and flow-transverse-momentum correlations. At the same time the required computational time decreases by several orders of magnitude. To demonstrate the advantage of the significantly reduced computation time, we generate ${10}^7$ initial energy density profiles from which we predict the flow observables using the neural network, which is trained using $5\times {10}^3$, and validated using $9\times {10}^4$ events per collision energy. We then show that increasing the number of collision events from $9\times {10}^4$ to ${10}^7$ can have significant effects on certain statistics-expensive flow correlations, which should be taken into account when using these correlators as constraints in the determination of the quantum chromodynamics matter properties.

Solar neutrino measurements have recently reached a level of sensitivity such that CNO fluxes can now be experimentally determined. While these first measurements are still only sensitive to the higher energy neutrinos resulting from the ${\beta }^{+}$ decays of ${}^{15}\mathrm{O}$ produced by the ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ reaction, future measurements will work towards detection of neutrinos from the ${\beta }^{+}$ decay of ${}^{13}\mathrm{N}$ from the ${}^{12}\mathrm{C}(p,\gamma ){}^{13}\mathrm{N}$ reaction. This paper reports on a recent measurement of the ${}^{12}\mathrm{C}(p,\gamma ){}^{13}\mathrm{N}$ reaction covering a broad laboratory energy range between 1.0 and 2.5 MeV. The measurement was made to better determine the overall normalization of the absolute cross section and to explore the interference effects between the two broad, overlapping resonances at proton energies of 0.460 and 1.689 MeV and the direct capture to the ground state of ${}^{13}\mathrm{N}$ in the framework of a multichannel $R$-matrix analysis. This work takes into account previous radiative capture as well as elastic ${}^{12}\mathrm{C}(p,p){}^{12}\mathrm{C}$ scattering data, making uncertainty estimations using a Bayesian framework, to determine a reliable extrapolation of the low energy $S$ factor towards the stellar energy range of CNO hydrogen burning. These new experimental results, and a detailed investigation of the past literature data, suggest that the resonant component of the cross section should be 30% lower than previously accepted.

The carbon burning process is a fundamental step of stellar evolution and governs the synthesis of chemical elements important for the formation of life. In this work, we utilize the microscopic hybrid $\alpha$-cluster $\left(\mathrm{H}\alpha \mathrm{C}\right)$ model and an analytical approach, both in the framework of the imaginary time method (ITM), to study the carbon fusion reaction towards zero energy. We obtain the values of the cross sections and astrophysical factors and we correlate our results to collective motion. We also include a calculation for the $2^{+}$ carbon fusion and discuss a possible experimental investigation. Our results confirm direct experimental and theoretical results close to the barrier, while suggesting possible $2^{+}$ mixtures in the indirect experimental data. Our study offers an accurate view of the burning process in the somewhat unexplored low energy region.

We report on the nature of ${}^{93m}\mathrm{Mo}$ isomer depletion as a result of nuclear excitation by electron capture in a resonant transfer process, accounting for highly excited open-shell atomic states to better reflect realistic beam-based conditions. The improved model provided an enhancement of ${}^{93m}\mathrm{Mo}$ depletion. The new probabilities for ${}^{93m}\mathrm{Mo}$ isomer depletion are compared with two available experimental results and previous models. The excited-state configurations provide probabilities that are a factor of about 20 higher than those obtained from the ground-state-configuration approach without Compton profiles.

The potential barriers in the cold fission valley were determined within the original generalized liquid drop model, which takes into account the proximity energy, the charge and mass asymmetries, the microscopic shell and pairing corrections, and quasimolecular one- and two-body shapes. Due to microscopic effects and the proximity energy, double-humped fission barriers appear. The calculations were done within four hypotheses for the heaviest proton magic number: 114, 116, 118, and 120. The calculated partial or total fission half-lives of actinides and superheavy nuclei follow roughly the trend of the experimental data, the agreement being better for $Z=118$.

In this paper a state-of-the-art version of the nucleon-pair approximation to the nuclear shell model is suggested. The configuration space is constructed by stepwise coupling collective nucleon pairs with given spin. The one-body and two-body matrix elements, as well as the overlaps, are calculated in terms of the $M$-scheme nucleon-basis states, without resorting to any angular momentum couplings. Many redundant commutations are avoided by using the Wigner-Eckart theorem and an algorithm similar to the coefficients of fractional parentage in the nuclear shell model calculations. Numerical experiments demonstrate the overwhelming computational superiority in comparison to all previous approaches of nucleon-pair shell model, particularly for the shell model Hamiltonian in the form of effective interactions. In addition, we exemplify this state-of-the-art version of the nucleon-pair approximation by even-even rare-earth ${}^{142–152}\mathrm{Nd}$ isotopes, for which the model space is constructed by using $SDGI$ nucleon pairs, and the Hamiltonian is adopted as $V_{\mathrm{low}\text{−}k}$ potential. Our calculation of the nucleon-pair approximation is able to reproduce reasonably the low-lying energy states of those Nd isotopes, where the seniority-type, vibrational, transitional, and rotational modes are described on the same footing, without adjusting any parameter.

The ${}^{25}\mathrm{Al}(p,\gamma ){}^{26}\mathrm{Si}$ reaction bypasses production of potentially observable ${}^{26}\mathrm{Al}$ in novae and strongly influences the nova contribution to galactic ${}^{26}\mathrm{Al}$. The nuclear structure of ${}^{26}\mathrm{Si}$ directly impacts estimates of the astrophysical ${}^{25}\mathrm{Al}(p,\gamma ){}^{26}\mathrm{Si}$ reaction rate, and reactions such as ${}^{28}\mathrm{Si}(p,t){}^{26}\mathrm{Si}$ have been used to understand this structure. Since the original publication of ${}^{28}\mathrm{Si}(p,t){}^{26}\mathrm{Si}$ data [D. W. Bardayan et al., Phys. Rev. C 65, 032801(R) (2002)], a number of subsequent publications have greatly clarified the level scheme of ${}^{26}\mathrm{Si}$, and this article reports on a reconsideration of these original data in light of the new results.

The neutron capture cross section and the capture $\gamma$-ray spectrum of ${}^{88}\mathrm{Sr}$ were measured in the keV energy regions: 10–89 keV and 510 keV. Between 34 and 89 keV, the present data are larger than evaluated cross sections which are based on a set of resonance parameters measured in past experiments. To investigate the impact of the present results to the stellar nucleosynthesis, the Maxwellian-averaged neutron capture cross section (MACS) was calculated using the present experimental results. The calculated MACS were about 10% smaller than the values from a previous work [Koehler et al., Phys. Rev. C 62, 055803 (2000)]. On the other hand, the present and previous MACS become in good agreement when the contribution from the direct neutron capture process that has been theoretically calculated is removed from the previous MACS. This suggests that the previous work might overestimate the contribution of the direct capture process. The present experimental capture $\gamma$-ray spectrum shows that primary transition intensities to the low-lying states of ${}^{89}\mathrm{Sr}$ drastically change with the neutron energy. The ratio between the ground and first excited state transitions was compared with estimation derived from the resonance parameters and theoretical prompt $\gamma$-ray spectrum from the $\left(lJ\right)$ neutron capture states. The estimation disagrees with the experimental values between 34 and 89 keV. This disagreement suggests that there are missed or $\left(lJ\right)$-misassigned resonances in the previous resonance analysis.

The characteristic cluster structures and low separation energies of weakly bound stable nuclei and their influence on the fusion process remain the subject of interest on experimental as well as theoretical fronts. To understand the fusion the dynamics of weekly bound nuclei, a comparison of fusion cross sections in reactions involving weakly bound projectiles ${}^{6,7}\mathrm{Li}$ on ${}^{235,238}\mathrm{U}$ targets was carried out within the collective clusterization approach of the dynamical cluster decay model (DCM) using deformed configuration effects included up to quadrupole deformations $\left({\beta }_{2i}\right)$ for two nuclei having optimum orientations ${\theta }^{\mathrm{opt}.}$ at similar center-of-mass energies $\left(E_{\mathrm{c}.\mathrm{m}.}\right)$. The fission excitation functions are tuned with respect to the available experimental data using the same neck length parameter $\left(\mathrm{\Delta }R\right)$, the only free parameter in the model. Signatures of fusion enhancement and incomplete fusion (ICF) were observed at below-barrier energies, which is consistent with the experimental results. The plausible segregation of CF (complete fusion) and ICF was also made within the formalism.

We recently introduced new concepts, implemented in EPOS4, which allows us to consistently accommodate factorization and saturation in high-energy proton-proton and nucleus-nucleus collisions in a rigorous parallel scattering framework. EPOS4 has a modular structure and in this paper, we present in detail how the “single scattering module” (the main EPOS4 building block) is related to perturbative QCD and how these calculations are performed, with particular care being devoted to heavy flavor contributions. We discuss similarities and differences compared to the usual pQCD approach based on factorization.

Background: Charged-current neutrino-nucleon reactions, generally called Urca processes, are crucial actors of a neutron star's thermal evolution. The so-called direct processes show a pronounced threshold under which the reaction is kinematically suppressed. This suppression does not apply to modified Urca processes, which involve interaction with an additional nucleon. Calculations of the modified Urca neutrino rates were established for cold neutron star matter and for dilute hot matter, in both cases under strong assumptions.

Purpose: In this paper, we revise the calculations of the modified Urca neutrino rates for dense and hot matter, and for different compositions. We study the influence of different approximations used in previous computations.

Methods: We derive expressions for the rates of modified Urca neutrino emissivity within thermal field theory and perform the phase space integration numerically using mainly importance sampling Monte Carlo techniques. The neutrino emissivity of modified and direct processes are established and compared.

Results: We find in particular that the modified Urca process is not necessarily suppressed with respect to the direct process above the threshold of the latter at moderate densities and temperatures, in contrast to what is generally assumed. Numerical results are confirmed by an estimation of the ratio of modified to direct Urca rates with a simple analytic approximation, thereby showing the regimes of suppression for the modified processes depending on temperature and density.

Conclusion: These results show that modified Urca rates have to be considered carefully upon evaluating neutrino opacities in dense and warm matter.

We report the first results from a new approach for measuring the ${}^3\mathrm{He}$ neutron incoherent scattering length $b_i$. $b_i$ is directly proportional to the difference $\mathrm{\Delta }b=b_{+}-b_{-}$ in the two low-energy $s$-wave neutron-nucleus scattering amplitudes $b_{+}$ and $b_{-}$, corresponding to the singlet $J=0$ and triplet $J=1$ states of the neutron-${}^3\mathrm{He}$ interaction, respectively. An accurate measurement of $b_i$ can help distinguish among different models of three-nucleon interactions by comparison to ab initio nuclear theory calculations. The neutron birefringence caused by $\mathrm{\Delta }b$ results in neutron spin rotation around the nuclear polarization. We measured $\mathrm{\Delta }b$ using polarized neutron spin rotation and the transmission of neutrons through a ${}^3\mathrm{He}$ gas target polarized in situ by spin-exchange optical pumping. This brief test measurement performed on the J-NSE Phoenix neutron spin echo spectrometer, yielded $\mathrm{\Delta }b=[-5.27\pm 0.05$ (stat.) $-0.05$ (syst.)] fm. We argue that this method can be improved in precision to resolve the discrepancies between two prior measurements of $b_i$ which are dependent on the polarized absorption cross section ${\sigma }_p$. With absolute ${}^3\mathrm{He}$ polarization measurement via nuclear magnetic resonance (NMR) (in a properly shaped cell) concurrent with accurate neutron transmission measurements, ${\sigma }_p$ can be measured to obtain independent values of $b_{+}$ and $b_{-}$.

We investigate the pairing properties of state-of-the-art semilocal coordinate-space and semilocal momentum-space regularized chiral interactions. Specifically, we calculate the pairing gaps in the ${}^{3}SD_1$ channel of symmetric nuclear matter and in ${}^1\mathrm{S}_0$ and ${}^{3}PF_2$ channels of pure neutron matter within the BCS approximation using these chiral interactions. We evaluate the truncation errors of chiral expansions of the pairing gaps with a Bayesian approach. We find overall weak regulator dependence and robust convergence from low to high densities for the ${}^{3}SD_1$ and ${}^1\mathrm{S}_0$ pairing gaps, while we find chaotic behavior for the ${}^{3}PF_2$ results. We compare the converged results of the chiral interactions with the results of the Argonne v18 (Av18) potential. Their discrepancies in the ${}^{3}SD_1$ and ${}^{3}PF_2$ channels at high densities demonstrate that the nucleon-nucleon interactions in these two channels may need further constraints at high scattering energies. We have also investigated the effect of the tensor force on the ${}^{3}SD_1$ and ${}^{3}PF_2$ pairing gaps. The apparently different tensor force effects of the chiral interactions and the Av18 potential for the ${}^{3}SD_1$ and ${}^{3}PF_2$ pairing gaps indicate that the tensor components of these interactions are quite different.

We investigate the influence of neutron emission in the fission of ${}^{227}\mathrm{Pa}$ populated by complete fusion of ${}^{19}\mathrm{F}$ with ${}^{208}\mathrm{Pb}$ at various excitation energies ($E^{*}$). Mass gated pre-scission neutron multiplicities (${\nu }_{\mathrm{pre}}$) were determined by fragment-neutron angular correlation and time of flight of fission fragments and neutrons using the National Array of Neutron Detectors facility. Obtained $\mathrm{Mass}-{\nu }_{\mathrm{pre}}$ correlation showed that, at lower $E^{*}=24.2$ and 32.4 MeV, larger ${\nu }_{\mathrm{pre}}$ is correlated with asymmetric mass division. On the other hand, at higher $E^{*}=46.1$ and 59.6 MeV, larger ${\nu }_{\mathrm{pre}}$ is correlated with symmetric mass division. The results were analyzed within the framework of the general description of fission observables GEneral description of Fission observables (GEF) model with multichance fission included. The analysis of fragment mass–total kinetic energy correlation for different chance fission clearly indicates a revival of shell effects at $E^{*}=24.2$ and 32.4 MeV as a consequence of sequential fission decay. At these energies, higher chance fission decreases the saddle point excitation energy considerably where shell effects are prominent. The interplay of shell mediated mass asymmetric fission and symmetric fission gives rise to an energy dependent $\mathrm{Mass}-{\nu }_{\mathrm{pre}}$ correlation. We have compared the experimental results with $\mathrm{Mass}-{\nu }_{\mathrm{pre}}$ correlation predicted by the GEF model. It is concluded that the correlation of larger ${\nu }_{\mathrm{pre}}$ with asymmetric mass at lower excitation energies is a signature of shell effects reinstated by sequential fission decay. At the two higher excitation energies, despite the multichance fission and consequent decrease in saddle point energy, the available excitation energy appears sufficient for the attenuation of shell effects.

A paramount goal in nuclear physics is to unify ab initio treatments of bound and unbound states. The position-space quantum Monte Carlo (QMC) methods have a long history of successful bound-state calculations in light systems but have seen minimal implementation in unbound systems. Here, we introduce a numerical method to improve the efficiency and accuracy of unbound-state calculations in QMC. As an initial application, we compute scattering observables for the smallest system available to probe three-body forces, the neutron-triton system, using variational Monte Carlo (VMC) wave functions. The method involves inferring long-range amplitudes in the wave function from integrals over the short-range region where all the particles interact. This approach using integral relations is well established in the literature; here, we develop it for the QMC framework. We validate our approach with a consistency check between short-range spectroscopic overlap functions computed from direct evaluation and from the integral relations; scattering amplitudes are long-range asymptotics of those overlaps. Comparison against published benchmark calculations using the same potential demonstrates that when applied to the current VMC wave functions, the integral method produces more accurate scattering observables than direct evaluation from the same variational wave function. However, it still differs noticeably from the exact results. Using additional interactions, we then present phase shifts and mixing parameters for the $n+{}^3\mathrm{H}$ system. In particular, we present one of the first applications of the Norfolk family of local coordinate-space chiral potentials in unbound systems of $A>2$. The Norfolk results accurately describe $s$-wave scattering but predict $p$-wave cross sections too large. Compared with previous QMC scattering calculations, the integral method avoids difficulties associated with the precise computation of energy differences and with convergence outside the interaction region, which is particularly severe in the variational calculation. Application of the integral method here paves the way for its use in Green's function Monte Carlo (GFMC) calculations. In GFMC, the wave functions are more accurate, but the high-precision convergence of their tails is slow, and there are additional difficulties in reading out amplitudes. The integral methods will address both of those remaining problems.

Production cross sections were measured for fragments produced by an 85 MeV/u ${}^{198}\mathrm{Pt}$ beam incident on a beryllium target. Event-by-event particle identification of $A, Z$, and $q$ for the reaction products was performed by employing energy loss, time-of-flight, magnetic rigidity, and total kinetic energy measurements. Over 70 nuclei in the Hf-Pt region were identified, including three isotopes first observed in this work: ${}^{191,192}\mathrm{Hf}$ and ${}^{189}\mathrm{Lu}$. Due to the existence of multiple charge states between H-like and C-like ions, a new analysis method was introduced, incorporating Monte Carlo calculations of charge state fractions for a given charge state of the projectile residue just after the reaction. For the first time, charge-state probability distribution functions after the reaction have been deduced from experimental data. This study provides insight into how to produce key nuclides near $N=126$ and the ability of a fragmentation residue to retain electrons from the primary beam.

In this study, we performed calculations and analyses of the structure functions of polarized nucleons and light nuclei, specifically ${}^3\mathrm{He}$ and ${}^3\mathrm{H}$, using second-order Feynman diagrams. Our investigation focused on two main aspects: First, we examined the symmetry properties of polarized light sea quarks. Second, we conducted a detailed investigation into the impacts of symmetry breaking on the structure functions of both nucleons and nuclei. To achieve this, we utilized the existing polarized parton distribution functions (polarized PDFs) available in the literature. These PDFs were used to calculate and compare the polarized structure functions $g_1$ and $g_2$ of the nuclei. Additionally, we examined and analyzed the Bjorken and Efremov-Leader-Teryaev sum rules by utilizing the moments of the polarized structure functions. The Lorentz color force components, namely $F_E^{y,n}$ and $F_B^{y,n}$, were determined using the twist-2, twist-3, and twist-4 matrix elements. When symmetry breaking is applied, it is observed that they have similar magnitudes but opposite signs. Our theoretical predictions for the polarized structure functions of nucleons and light nuclei, taking into account the symmetry breaking of light sea quarks, exhibit better agreement with experimental data.

The effects of the pairing force on the fission process including static and dynamics aspects are systematically studied, taking the induced fission of ${}^{240}\mathrm{Pu}$ as an example. The Skyrme density functional theory (DFT) is adopted to calculate the static potential energy surface (PES), the nucleon localization function, etc. with the Hartree-Fock-Bogoliubov (HFB) and the HFB–Lipkin-Nogami (HFBLN) methods for the static part. The fission dynamics is studied based on the time-dependent generator coordinate method (TDGCM). The sensitivity of the calculation results to the pairing force is investigated by reducing and enhancing its strength from the normal one by 10%. Our results show that the pairing force plays a significant role in many aspects of the fission process. A very sensitive dependence of the mass tensor on the pairing strength is found, which has an obvious impact on the fission dynamics. The fission yields of ${}^{240}\mathrm{Pu}$ with the normal pairing strength are consistent with the experimental data. However, the distribution of calculated fission yields becomes quite narrow for both enhanced and reduced pairing force cases, while the peak of the yields stays at the asymmetric fission side in the case of the reduced pairing strength, but in the case of enhanced pairing force it shifts toward the symmetric fission side. For the normal pairing force strength, our study shows that the calculated fission yield does not sensitively depend on the parameter related to the average particle number in the neck region for the determination of the scission line in the TDGCM approach within a reasonable range. It indicates that the fragments are formed early during the elongation of the fissioning nuclei, and a proper pairing force is essential for fission fragment distribution calculations.