The pre- and postscission neutron multiplicities have been determined for the fission of the compound nucleus (CN) ${}^{206}\mathrm{Rn}$, induced by the reaction ${}^{28}\mathrm{Si}+{}^{178}\mathrm{Hf}$ within the excitation energy interval of 61.0–90.0 MeV. We intentionally formed the CN ${}^{206}\mathrm{Rn}$, which is below the shell closure CN, to examine the variation in N/Z with total neutron multiplicity, as data for other compound nuclei of ${}^{208,210,212,214,216}\mathrm{Rn}$ have already been published in the literature. The present experimental investigations between N/Z and total multiplicities validate the theoretical claims made by various calculations. Specifically, it was observed that the total neutron multiplicity decreases as the compound nucleus approaches the shell closure and subsequently increases as it moves away from the shell closure. Furthermore, we have observed that, below the neutron shell closure, the dissipation in compound nuclei escalates with rising excitation energy, remains stable at the shell closure CN, and thereafter diminishes with increasing excitation energy above the shell closure CN.

We apply the nonequilibrium Green's function (NEGF) method to microscopically evaluate fission cross sections for the neutron induced ${}^{235}\mathrm{U}(n,f)$ reaction. While the model space was restricted only to seniority zero configurations in the previous applications of the NEGF method, we remove this restriction and include seniority nonzero configurations as well. In such a model space, a proton-neutron interaction is active, for which we introduce a random interaction. We find that the seniority nonzero configurations significantly increase the fission cross sections, and thus the fission-to-capture branching ratios, even though they are still underestimated by about one order of magnitude as compared to the experimental data. In addition, we also find that the fission dynamics is governed by only a small number of eigenstates of the model Hamiltonian.

In the present work, based on the deformed Gamow-like model, we quantitatively investigate the effect of ultra-intense laser fields on the cluster radioactivity process. The calculated results indicate that the cluster radioactivity penetration probability can be altered by ultra-intense laser fields to some finite extent. In addition to numerical results, a modified approximate formula to rapidly estimate and obtain a more reasonable value for the rate of change of the cluster radioactivity penetration probability is provided. Furthermore, we study the correlation between the decay energy of different cluster radioactivity nuclei and the maximum instantaneous rate of change of the cluster radioactivity penetration probability. The results show that for nuclei emitting the same type of cluster, those with lower decay energy are more susceptible to ultra-intense laser fields. The relationship between laser characteristics and the average rate of change of the cluster radioactivity penetration probability is also discussed. The calculations display that lasers with shorter wavelength have a more pronounced effect on the average rate of change in pulse duration. Finally, utilizing the deformed Gamow-like model, we predict the half-lives of potential cluster radioactive candidates and explore the influence of laser pulse on them to determine the possible experimental object of the laser-assisted cluster radioactivity.

The nature and structure of high-energy resonance states in ${}^8\mathrm{Be}$, located just below and above the $p+{}^7\mathrm{Li}$ threshold, are investigated in detail. A microscopic many-cluster and many-channel model is employed to study the formation of these resonances. This model includes three distinct three-cluster configurations: ${}^4\mathrm{He}+{}^3\mathrm{H}+p$, ${}^4\mathrm{He}+{}^3\mathrm{He}+n$, and ${}^4\mathrm{He}+d+d$, enabling a comprehensive treatment of all major binary decay channels of ${}^8\mathrm{Be}$, namely ${}^4\mathrm{He}+{}^4\mathrm{He}$, $p+{}^7\mathrm{Li}$, $n+{}^7\mathrm{Be}$, and $d+{}^6\mathrm{Li}$. The primary focus of our analysis is the structure and dominant decay channels of the twin $1^{+}$, $2^{+}$, $3^{+}$, and $4^{+}$ resonance states. Additionally, we propose and implement a model to clarify how the $2^{+}$ resonance states lying below the $p+{}^7\mathrm{Li}$ threshold are formed. We demonstrate that these resonances are Feshbach-type states arising due to coupling of the open ${}^4\mathrm{He}+{}^4\mathrm{He}$ channel with the closed channels $p+{}^7\mathrm{Li}$, $n+{}^7\mathrm{Be}$, and $d+{}^6\mathrm{Li}$ at these energies. Overall, the present approach provides a realistic description of the experimentally observed resonance spectrum near the ${}^7\mathrm{Li}+p$ decay threshold, including negative-parity states $1^{-}$ and $2^{-}$. Our results are consistent with other microscopic calculations but offer more detailed insight into the internal structure and decay pathways of these resonances.

Background: Data on reaction cross section ${\sigma }_R$ of proton scattering are available for ${}^{\mathrm{nat}}\mathrm{Pb}$ (natural lead) and ${}^{159}\mathrm{Tb}$. In addition, data on ${\sigma }_R$ and/or interaction ones ${\sigma }_I$ are available for Mg, Na, and Ar isotopes.

Purpose: Our aim is to determine neutron skin thickness $r_{\mathrm{skin}}$ for ${}^{\mathrm{nat}}\mathrm{Pb}$ and ${}^{159}\mathrm{Tb}$ and to investigate effects of deformation for Mg, Na, and Ar isotopes.

Methods: We use the chiral (Kyushu) $g$-matrix folding model for lower energies and the folding model based on the Love-Franey (LF) $t$-matrix for higher energies.

Results: For ${}^{159}\mathrm{Tb}$, our skin value is $r_{\mathrm{skin}}=0.273\pm 0.073$ fm. As for ${}^{24}\mathrm{Mg}$, our matter radius $r_m\left({\sigma }_R\right)=3.03\pm 0.08$ fm determined from ${\sigma }_R$ includes effects of deformation, whereas the corresponding $r_m\left({\sigma }_I\right)=2.79\pm 0.15$ fm does not. Effects of deformation are seen for Mg isotopes, ${}^{21,23}\mathrm{Na}$, and ${}^{40}\mathrm{Ar}$.

Conclusion: Our result $r_{\mathrm{skin}}=0.271\pm 0.008$ fm for ${}^{\mathrm{nat}}\mathrm{Pb}$ agrees with $r_{\mathrm{skin}}^{208}\left(\mathrm{PREX}\text{−}\mathrm{II}\right)=0.283\pm 0.071$ fm for ${}^{208}\mathrm{Pb}$, where we assume $A=208$ for ${}^{\mathrm{nat}}\mathrm{Pb}$.

Driven by recent laboratory experiments and astronomical observations, significant advances have deepened our understanding of neutron-star physics. NICER's Pulse Profile Modeling has refined our knowledge of neutron star masses and radii, while gravitational-wave detections have revealed key insights into the structure of neutron stars. Particularly relevant is the extraction of the tidal deformability by the LIGO-Virgo collaboration and the most recent determination of stellar radii by NICER, both suggesting a relatively soft equation of state (EOS) at intermediate densities. Additionally, measurements from the PREX collaboration and from pulsar timing suggest instead that the EOS is stiff in the vicinity of saturation density and at the highest densities accessible to date. But how stiff can the EOS be at these very high densities? Recent events featuring compact objects near the “lower mass gap” have raised questions about the existence of very massive neutron stars. Motivated by this finding and in light of new refinements to theoretical models, we explore the possibility that these massive objects may indeed be rapidly rotating neutron stars. We explore how rotation affects both the maximum neutron star mass and their associated radii, and discuss the implications they may have on the equation of state.

Nuclear physics seeks to describe both bound and unbound states within a unified predictive framework. While coordinate-space quantum Monte Carlo (QMC) methods have successfully computed bound states for systems with $A\le 12$, their application to unbound states remains limited. In this work, we advance the QMC approach by implementing the integral relations method within the Green's function Monte Carlo (GFMC) framework, representing a significant methodological advance. This method infers long-range amplitudes in the wave function from integrals over the short-range interaction region. By evaluating these integrals using GFMC wave functions with the Argonne $v_{18}$ potential, we validate the approach by accurately reproducing neutron–$\alpha$ phase shifts, in agreement with existing benchmarks. This approach provides a systematic pathway for studying more complex nuclear systems, including coupled-channels scattering and the effects of three-nucleon forces. It is a powerful tool for advancing ab initio calculations in nuclear reactions, paving the way for a unified framework that consistently describes bound and scattering states within a single theoretical approach.

This paper describes the development of the Four Model Tree Ensemble (FMTE). The FMTE is a composite of machine learning models trained on experimental binding energies from the Atomic Mass Evaluation (AME) 2012. The FMTE predicts binding energy values for all nuclei with $N>7$ and $Z>7$ from AME 2020 with a standard deviation of 76 keV and a mean average deviation of 34 keV. The FMTE model was developed by combining three new models with one prior model. The new models presented here have been trained on binding energy residuals from mass models using four machine learning approaches. The models presented in this work leverage shape parameters along with other physical features. We have determined the preferred machine learning approach for binding energy residuals is the least-squares boosted ensemble of trees. This approach appears to have a superior ability to both interpolate and extrapolate binding energy residuals. A comparison with the masses of isotopes that were not measured previously and a discussion of extrapolations approaching the neutron drip line have been included.

Neutrinoless double-beta decay of nuclei represents one of the most promising methods for uncovering physics beyond the standard model. In this context, ${}^{76}\mathrm{Ge}$ stands out as a particularly attractive candidate, as it can serve as an intrinsic component in semiconductor detectors. If the neutrinoless process occurs in ${}^{76}\mathrm{Ge}$, its signature would appear as a distinct peak at the $Q$ value of $2039\mathrm{keV}$. A neutron activation measurement was performed on a germanium sample isotopically enriched in ${}^{76}\mathrm{Ge}$ at the DT neutron generator of TU Dresden. The measurement confirmed the presence of $\gamma$ rays with energies of $2033.1\pm 0.5\mathrm{keV}$, $2035.5\pm 0.4\mathrm{keV}$, and $2040.22\pm 0.26\mathrm{keV}$ originating from the decays of ${}^{74}\mathrm{Ga}$ and ${}^{76}\mathrm{Ga}$. These $\gamma$ rays lie in close proximity to the expected neutrinoless double-beta decay signal of ${}^{76}\mathrm{Ge}$.

There is a growing body of evidence highlighting that multinucleon transfer (MNT) reactions offer a unique advantage in synthesizing neutron-rich nuclei within the $N=126$ region. However, forecasting the yields of products for specific projectile and target combinations, as well as their corresponding detection areas, remains theoretically challenging. This research aims to investigate the impact of different incident energies and projectile-target combinations on the yields of the MNT process in the terra incognita region of nuclei around $N=126$ based on the improved CLIM-H model. We systematically test the current model against well-measured MNT reactions, including ${}^{136}\mathrm{Xe}+{}^{209}\mathrm{Bi}$, ${}^{136}\mathrm{Xe}+{}^{238}\mathrm{U}$, and ${}^{136}\mathrm{Xe}+{}^{198}\mathrm{Pt}$. The production of nuclei with $N=126$ in these reactions is specifically studied and compared. Additionally, the use of heavy radioactive isotopes as projectiles in MNT reactions is explored. Findings indicate that for the unknown nuclei ${}^{203}\mathrm{Ir}_{126}$, ${}^{202}\mathrm{Os}_{126}$, ${}^{201}\mathrm{Re}_{126}$, ${}^{200}\mathrm{W}_{126}$, and ${}^{199}\mathrm{Ta}_{126}$, the total cross sections in ${}^{210}\mathrm{Pb}+{}^{198}\mathrm{Pt}$ are significantly higher compared to other reactions. The suitable angular distribution for detecting the above isotopes is also presented.

The yrast states in even-even $N=80$ nuclei are studied within the frameworks of both the large-scale shell model and the nucleon-pair approximation by using optimized effective interaction. Both calculations reproduce most of the experimental data for yrast $2_1^{+}\text{−}{8}_1^{+}$ states. Abrupt inconsistency between these two sets of calculations for the ${10}_1^{+}\text{−}{16}_1^{+}$ states is found to be a reflection of the type-II shell evolution, which is also seen in the effective single-particle energies of proton levels, at the ${10}_1^{+}$ states. This suggests a strong correlation between the type-II shell evolution and the evolution of nucleon-pair structure, which leads to fragility of optimized nucleon pairs of the ground states for states with spins higher than ten. By further consideration of nucleon pairs specifically optimized for the ${10}_1^{+}$ state with a new variational procedure in our configuration space, we are able to improve substantially the consistency between calculated results in the nucleon-pair approximation and those of the exact shell-model calculation.

Background: Single-crystal chemical vapor deposited (sCVD) diamond detectors offer a unique method to study cross sections of reactions on carbon since they can be used as active targets. Previous studies analyzing neutrons on carbon using these detectors were primarily focused on lower-energy neutrons and reactions, and some of these did not have sufficient energy resolution to isolate the contributions of reaction channels with similar Q values.

Purpose: This work extends neutron-induced reaction cross section measurements to higher energies, relevant to rare isotope facilities. These measurements can be used to inform and benchmark simulation of experiments that require neutron detection, particularly those utilizing organic scintillators. For some experiments, simulations are used to extract physics information from experimental data, reinforcing the need for accurate simulations.

Methods: Two sCVD diamond detectors were used as active targets at the Los Alamos Neutron Science Center (LANSCE), where neutrons up to 800 MeV are produced via spallation.

Results: Relative cross sections are reported from incident neutron (kinetic) energies $E_n=12$ MeV up to 55 MeV for ${}^{12}\mathrm{C}(n,{\alpha }_0)$, up to 46 MeV for ${}^{12}\mathrm{C}(n,d_0)$, and up to 27 MeV for ${}^{12}\mathrm{C}(n,p_0)$ and ${}^{12}\mathrm{C}(n,p_1)$. These measurements extend these cross sections to energies higher than those of previous studies.

Conclusions: Good agreement is found between this work and recent experimental data from the EXFOR database in the neutron energies where the studies overlap. This work supports the need to update the ENDF evaluation for the ($n,{\alpha }_0)$ channel with more recent data and provides data that could allow for an evaluation of the ($n,p_0$), ($n,p_1$), and ($n,d_0$) channels. These cross sections will increase the accuracy of simulations by extending the energy range for which empirical cross sections are available and including new reaction channels.

The pseudorapidity density distributions of charged particles and the transverse-momentum spectra of identified particles in proton-proton ($pp$) collisions at the center-of-mass energies ranging from $\sqrt{s}=200$ GeV to 13 TeV have been systematically studied using the newly released parton and cascade model paciae 4.0 based on pythia 8.3. The available experimental data are well reproduced across all analyzed aspects. This theoretical method can be easily extended to anywhere the experimental data for $pp$ collisions are currently unavailable. Furthermore, since $pp$ collisions serve as the baseline for heavy-ion collisions, our results can provide a valuable resource for both experimentalists and theorists.

We investigate the volume and lifetime of the high-baryon-density matter created in heavy-ion collisions and estimate the optimal collision-energy range to realize the high-baryon-density region over a large space-time volume. We simulate central collisions of gold ions for the center-of-mass energy per nucleon pair $\sqrt{s_{NN}}=2.4-19.6\mathrm{GeV}$ with a microscopic transport model JAM. We discover that the optimal range is around $\sqrt{s_{NN}}=3-5\mathrm{GeV}$, where a baryon density exceeding three times the normal nuclear density is realized with a substantially large space-time volume. Higher and lower energies are disfavored due to short lifetime and low density, respectively. We also point out that event-by-event fluctuations of the space-time density profile are large, indicating the importance of the event selection in the experimental analysis.

The Young-Koppel (YK) model describes comprehensively the interaction of slow neutrons with diatomic gases such as ${\mathrm{H}}_2$ and ${}^2\mathrm{H}_2$. This paper reports on the first experimental results of ultracold neutron (UCN) scattering over a wide temperature range vindicating the YK model for gaseous ${}^2\mathrm{H}_2$ and showing an important difference in the temperature dependence to a low-energy low-temperature approximation (LETA). LETA is confirmed, however, to be valid for monoatomic gases such as Ne. Calculated cross sections for other noble gases were also confirmed for ultracold neutrons. Finally, the total cross section of UCNs in ${\mathrm{H}}_2$ gas was measured and analyzed applying the Young-Koppel model, however, in a more limited temperature range, confirming the theoretical prediction.

This work reports on the study of the decay properties along the ${}^{257}\mathrm{Db}$ decay chain using the GABRIELA setup. The first observation of a high-K isomer in ${}^{257}\mathrm{Db}$ is presented. In addition, an unreported $\alpha$-decay branch in ${}^{249}\mathrm{Md}$ has been evidenced, allowing constraints the differences in energy of the $\alpha$-decaying levels in ${}^{249}\mathrm{Md}, {}^{253}\mathrm{Lr}$ and ${}^{257}\mathrm{Db}$. Finally, the combination of the observed fine structure $\alpha$-decay from the high-spin state in ${}^{257}\mathrm{Db}$ with the first observation the internal decay in ${}^{253}\mathrm{Lr}$ requires a revision of the level and decay scheme. In particular, a change of parity for the high-spin state from $9/2^{+}$ to $9/2^{-}$ in ${}^{257}\mathrm{Db}$ is suggested, and the implications of such a change are also discussed.

Background: With the recent lifetime measurements of the $2^{+}$ states in ${}^{116}\mathrm{Te}$ and ${}^{118}\mathrm{Te}$, the evolution of the collectivity in the midshell region of the Te isotopic chain is starting to reveal itself. However, more information on the structure of the ground-state bands and the nature of the collectivity can be gathered from studying the odd-mass systems, in which lifetimes have not been extensively studied.

Purpose: The purpose of the present work is to investigate the structure of low-lying excited states of the $\nu h_{11/2}$ band in the odd-mass systems ${}^{117}\mathrm{Te}$ and ${}^{119}\mathrm{Te}$, that correspond to the ground-state band in even-even Te.

Methods: Lifetimes of low-lying states in the $\nu h_{11/2}$ band of ${}^{117}\mathrm{Te}$ are measured for the first time and remeasured in ${}^{119}\mathrm{Te}$, using the recoil distance Doppler shift technique, and analyzed with the differential decay curve method in coincidence mode.

Results: The lifetimes and $B$(E2) values of the first two transitions, $15/2^{-}\to 11/2^{-}$ and $19/2^{-}\to 15/2^{-}$, in the $\nu h_{11/2}$ band, are determined in both ${}^{117}\mathrm{Te}$ and ${}^{119}\mathrm{Te}$. From the lifetimes, the $B$(E2) values and corresponding $B_{4/2}$ ratios are determined. The results are compared to systematics in both even-$A$ and odd-$A$ Te isotopes, as well as with theoretical results from the large-scale shell model and interacting boson model calculations.

Conclusions: While the energy levels of ${}^{117}\mathrm{Te}$ and ${}^{119}\mathrm{Te}$, similarly to ${}^{118}\mathrm{Te}$, exhibit textbook vibrational behavior, the unexpectedly small $B_{4/2}$ ratios of these odd-mass nuclei point to a puzzling discrepancy and question the vibrational nature of these states.

Background: Searching for $\alpha$ condensation around a core nucleus, a new class of nuclear clustering, is an interesting topic. Previous theoretical studies predicted ${}^{16}\mathrm{O}+2\alpha$ condensed states. However, in those studies, the strong mixing with nonresonant states made the identification of true resonant states nontrivial.

Purpose: To address this issue, we aim to provide a more robust theoretical verification of the ${}^{16}\mathrm{O}+2\alpha$ condensation. Our goal is to clearly identify the resonant states and predict their properties, such as decay widths.

Method: We employ the real-time evolution method (REM), which generates physically important basis states using the equation of motion, minimizing contamination from the continuum. The analytical continuation in the coupling constant (ACCC) was used to estimate the $\alpha$-decay widths.

Results: The present calculations show much better convergence of eigenstates, and the $0_3^{+}$ and $0_4^{+}$ states show remarkable isoscalar monopole transition strengths, which are in good agreement with the predictions of Ichikawa et al. The small $\alpha$-decay widths for these states suggest that experimental observation appears feasible.

Conclusion: The present results show the reasonable agreement with a previous work, firmly establishing the $0_3^{+}$ and $0_4^{+}$ states approximately 5 and 1 MeV below the ${}^{16}\mathrm{O}+2\alpha$ threshold as candidates for the $2\alpha$ condensation around the core nucleus ${}^{16}\mathrm{O}$. The REM proved effective in identifying these states.

Silicon has become an unavoidable element in the circuitry central to everyday life. In turn, the interactions of silicon isotopes with neutrons for nuclear physics applications, among other motivations, have become increasingly important to understand. The dominant isotope of silicon, ${}^{28}\mathrm{Si}$, is thus of primary interest for enhanced understanding for neutron transport calculations and related investigations. Unfortunately, the existing measurement database for neutron scattering reactions on ${}^{28}\mathrm{Si}$ is minimal, and nuclear data evaluations on this topic have not been updated for decades. This article details new measurements of the ${}^{28}\mathrm{Si}(n,n^{\prime }\gamma )$ reaction utilizing multiple analysis methods available within the correlated gamma neutron array for scattering (CoGNAC). Specifically, high-precision near-threshold results and high-incident-energy results were obtained using the $\gamma$-only and correlated $n\text{−}\gamma$ techniques. First-ever measurements of the correlated $n\text{−}\gamma$ angular distribution for particles emitted following population of the first excited state in ${}^{28}\mathrm{Si}$ were obtained as well, which provide unique insight into theoretical descriptions of the inelastic neutron scattering reaction mechanism itself and detailed guidance for nuclear reaction models. The results agree well with literature data where they exist, and substantially expand on the current database for neutron reactions on ${}^{28}\mathrm{Si}$.

We have studied ${}^{32}\mathrm{Si}$ and ${}^{29}\mathrm{Al}$ using ${}^{12}\mathrm{C}({}^{22}\mathrm{Ne},2\mathrm{p})$ and ${}^{12}\mathrm{C}({}^{22}\mathrm{Ne},\alpha \mathrm{p})$ fusion-evaporation reactions. In both cases, we observed significant population of high-spin structures distinct from the ground-state yrast bands. In ${}^{32}\mathrm{Si}$, most of the high-energy states feed into a $J^{\pi }=5^{-}$ nanosecond isomer. In ${}^{29}\mathrm{Al}$, we identified a rotor-like negative-parity band with a $J^{\pi }=7/2^{-}$ band-head. Doppler shift lifetime measurements were performed for all observed states. These results were compared to shell model calculations and interpreted in terms of proton and neutron cross-shell excitation.