We examine the validity of surface approximation for breakup reactions using a fully quantum-mechanical model proposed by Ichimura, Austern, and Vincent (IAV). Analogous to the semiclassical picture, we introduce radial cut-offs to scattering waves in the IAV framework, which we refer to as IAV-cut. Systematic calculations are conducted for nonelastic breakup reactions induced by ${}^6\mathrm{Li}$ and deuterons at various incident energies. A comparison between the results obtained from IAV and IAV-cut is performed. The excellent agreement observed between IAV and IAV-cut in ${}^6\mathrm{Li}$ induced reactions, regardless of incident energy and target nuclei, signifies their insensitivity to the inner part of the scattering wave function, thus providing validation for the semiclassical picture. However, for deuteron induced breakup reactions, the IAV-cut results exhibit a suppression in the cross section, suggesting a strong dependence on the interior wave functions. This suppression is further enhanced as the incident energy increases.

The collective flow generated in relativistic heavy-ion collisions fluctuates from event to event. The fluctuations lead to a decorrelation of flow vectors measured in separate bins in phase space. These effects have been measured in experiments and observed in numerical simulations in hydrodynamic models. We present a simple random model of flow decorrelation in pseudorapidity. Analytical expressions for the flow factorization breaking coefficients for flow vectors, flow vector magnitudes, and flow angles are derived. The model explains the relations between different factorization breaking coefficients found in experimental data and model simulations. In particular, it is found that the flow angle decorrelation constitutes about one half of the total flow vector decorrelation.

In this work, we explore the properties of isospin asymmetric quark matter in quark stars (QSs). The isospin chemical potential, the isospin asymmetry, the quark matter symmetry energy, the equation of state (EOS) of strange quark matter (SQM), and the maximum mass of QSs are also studied by using different quark phenomenological models. Our results indicate that the parameter space of the quark phenomenological models for the quark matter symmetry energy and the EOS of the star matter can be reduced by considering the recent mass-radius estimates of PSR $\mathrm{J}0740+6620$, PSR $\mathrm{J}0030+0451$, 4U 1702-429, and the central compact star within the supernova remnant HESS J1731-347.

The equation of state of neutron-rich nuclear matter is of interest to both nuclear physics and astrophysics. We have demonstrated the consistency between laboratory and astrophysical nuclear matter in neutron stars by considering low-density nuclear physics constraints (from ${}^{208}\mathrm{Pb}$ neutron-skin thickness) and high-density astrophysical constraints (from neutron star global properties). We have used both quark-level and hadron-level models, taking the quark mean-field (QMF) model and the relativistic mean-field (RMF) model as examples, respectively. We have constrained the equation of states of neutron stars and some key nuclear matter parameters within the Bayesian statistical approach, using the first multimessenger event GW170817/AT 2017gfo, as well as the mass-radius simultaneous measurements of PSR $\mathrm{J0030}+0451$ and PSR $\mathrm{J0740}+6620$ from NICER, and the neutron-skin thickness of ${}^{208}\mathrm{Pb}$ from both PREX-II measurement and ab initio calculations. Our results show that, compared with the RMF model, the QMF model's direct coupling of quarks with mesons and gluons leads to the evolution of the in-medium nucleon mass with the quark mass correction. This feature enables the QMF model a wider range of model applicability, as shown by a slow drop of the nucleon mass with density and a large value at saturation that is jointly constrained by nuclear physics and astronomy.

In this work, we carried out a detailed study of the factors affecting the fission dynamics of selected even-even actinide nuclei within a quasiclassical statistical approach based on the Langevin formalism. Essentially, the influence of initial conditions and geometrical criteria for spontaneous and induced fission of ${}^{236}\mathrm{U}$ as for the test case are worked out and then, using the knowledge thus acquired, we perform more extensive calculations for selected nuclei of $\mathrm{U}, \mathrm{Pu}, \mathrm{Cm}, \mathrm{Cf}$, and $\mathrm{Fm}$ isotopic chains. Potential energy surfaces (PES) are calculated within a macroscopic-microscopic approach in a three-dimensional space of the so-called Fourier deformation parameters representing the square of surface radius function in cylindrical coordinates. We also use the Lublin-Strasbourg Drop and folded-Yukawa mean-field models to estimate the full PES for these isotopes. The restoration of the particle number in the superfluid BCS-like approach is realized within the generator coordinate method with the Gaussian Overlap Approximation in the one-dimensional gauge-angle space. The tensors of inertia and friction, which play the role of transport coefficients, are given respectively within the hydrodynamic Werner-Wheeler approximation and what we usually call the “wall” formula. The main part of our research focuses on studying the conditions imposed on the solutions of the Langevin equations. In particular, we analyze the effect of the initial point distribution used to generate Langevin trajectories on resulting fragment mass and total kinetic energy distributions. Furthermore, we derive a way to optimize the size of the neck showing up on a nuclear surface in the final stage of its evolution to fission, taking into account the random and sudden natures of its rupture. Neck thicknesses generated with an appropriate normal distribution reproduce reasonably well the empirical fragment mass distributions in the lighter actinides along various excitation energies. However, for heavier actinides, such as $\mathrm{Cf}$ and $\mathrm{Fm}$, the capability of our model to reproduce the final fragmentation seems to be limited.

As part of an effort to better understand the structure of neutron-rich, rare-earth nuclei that are involved in the $r$ process, an experiment aimed at the ${\beta }^{-}$-decay spectroscopy of ${}^{157}\mathrm{Nd}$ was performed. The CARIBU source provided an isobarically separated $A=157$ beam which was delivered to the SATURN decay station at Argonne National Laboratory. A half-life of $t_{1/2}=1.17\left(4\right)$ s was measured for the ${}^{157}\mathrm{Nd}$ decay, which is in agreement with a previously reported value. A level scheme based on the ${}^{157}\mathrm{Nd}{\beta }^{-}$ decay was established for the first time. The level at 1703 keV in the daughter ${}^{157}\mathrm{Pm}$ nucleus was assigned the $\pi \mathrm{7/2[523]}$ configuration and it was found to be populated quite strongly as a result of an allowed-unhindered “spin-flip” transition from the $\nu \mathrm{5/2[523]}$ ground state in ${}^{157}\mathrm{Nd}$.

Nuclear isomers provide an opportunity to investigate the role of the single-particle configuration and its exotic rearrangements in nuclear stability, away from the shell closures. We explored the configurations of translead isomers from Pb to U and their stability relative to ground states, and then we investigated their well-defined $\alpha$-decay modes relative to the ground-state decays. The $\alpha$-preformation probability $S_{\alpha }$ is deduced from the experimental half-life and that calculated without implementing $S_{\alpha }$, within the preformed cluster model based on the Wentzel–Kramers–Brillouin tunneling penetrability and assault frequency in terms of the Skyrme $\alpha +$ core potential. We found that the single valence $Z=83,85,87$ protons ($\pi 1h^{1,3,5}{}_{{9/2}^{-}}$) and $N=127$ neutron ($\nu 2g^1{}_{{9/2}^{+}}$) outside the doubly magic Pb core play a main role in enhancing the stability of translead isomers, whether they last in the original orbital or promote to another one, solely or coupled to another valence nucleon. The spin-gap isomers of high spin may be attributed to coupling of two protons or neutrons to stretched large spin, and then they jointly couple with a single valence nucleon. For favored $\alpha$ decays, the isomers indicate larger $\alpha$-preformation probability than ground states. The decays from isomeric states of lower energy to higher daughter states and that involve a change in parity exhibit not only less $S_{\alpha }$ but also less relative stability than the higher-to-lower decays and those keep the parity unchanged, respectively. Increasing the difference in spin of the isomer relative to its daughter nucleus is found to enhance its stability, yielding larger half-live and smaller preformation probability.

With the recent emergence of fast nuclear reactors, there has been a corresponding increasing interest in ${}^{238}\mathrm{U}$-related nuclear data. However, while existing literature data span much of the energy ranges of interest for the prompt fission neutron spectrum (PFNS) for neutron-induced fission of ${}^{238}\mathrm{U}$, most literature data sets are highly correlated, and thus new, independent measurements of this quantity are needed. In this work, we report the results of a new measurement of the ${}^{238}\mathrm{U}$ PFNS at the Los Alamos Neutron Science Center for incident neutron energies from 1.5–20.0 MeV, and outgoing neutron energies of 0.01–10.0 MeV. With some notable exceptions, the present results generally agree with existing literature data, especially with regard to features relating to multichance fission and pre-equilibrium features in the PFNS, thus adding confidence to existing nuclear data evaluations and filling in gaps of knowledge at previously unmeasured incident neutron energies. This result is the third in a series of PFNS measurements by the Chi-Nu collaboration now spanning all three major actinides, ${}^{239}\mathrm{Pu}$, ${}^{235}\mathrm{U}$, and ${}^{238}\mathrm{U}$. Thus, for the first time, we report reliable experimental PFNS ratios and average PFNS energy comparisons for measurements of all three of these isotopes including accurate correlations between the different, but correlated experiments.

Background: Systematic measurement of $t$ and ${}^3\mathrm{He}$ knockout processes is planned. The weakly-bound nature of these nuclei may affect the interpretation of forthcoming knockout reaction data.

Purpose: We aim at clarifying breakup properties of $t$ and ${}^3\mathrm{He}$ by investigating their elastic and breakup cross sections.

Methods: We employ the four-body continuum-discretized coupled-channels method with the eikonal approximation to describe the reactions with $t$ and ${}^3\mathrm{He}$ projectiles.

Results: The breakup cross section of $t$ is found to be almost the same as that of ${}^3\mathrm{He}$ and is about one-third of that of $d$. Coulomb breakup plays negligible role in the breakup of $t$ and ${}^3\mathrm{He}$, in contrast to in the deuteron breakup reaction. It is found that $t$ and ${}^3\mathrm{He}$ tend to break up into three nucleons rather than $d$ and a nucleon.

Conclusions: It is shown that the breakup cross sections of $t$ and ${}^3\mathrm{He}$ are not as large as those of $d$ but non-negligible. Because about 80% of them corresponds to the three-nucleon breakup process, a four-body breakup reaction model is necessary to quantitatively describe the breakup of $t$ and ${}^3\mathrm{He}$.

Quasielastic scattering on ${}^{12}\mathrm{C}(e,e^{\prime }p)$ was measured in Hall C at Jefferson Lab for spacelike four-momentum transfer squared $Q^2$ in the range of $8\text{–}14.2{(\mathrm{GeV}/c)}^2$ with proton momenta up to $8.3\mathrm{GeV}/c$. The experiment was carried out in the upgraded Hall C at Jefferson Lab. It used the existing high-momentum spectrometer and the new super-high-momentum spectrometer to detect the scattered electrons and protons in coincidence. The nuclear transparency was extracted as the ratio of the measured yield to the yield calculated in the plane wave impulse approximation. Additionally, the transparency of the $1s_{1/2}$ and $1p_{3/2}$ shell protons in ${}^{12}\mathrm{C}$ was extracted, and the asymmetry of the missing momentum distribution was examined for hints of the quantum chromodynamics prediction of color transparency. All of these results were found to be consistent with traditional nuclear physics and inconsistent with the onset of color transparency.

Studies attempting to quantify the sensitivity of the $r$-process abundances to nuclear input have to cope with the fact that the theoretical models they rely on, rarely come with confidence intervals. This problem has been dealt with by either estimating these intervals and propagating them statistically to the final abundances using reaction networks within simplified astrophysical models, or by running more realistic astrophysical simulations using different nuclear-physics models consistently for all the involved nuclei. Both of these approaches have their strengths and weaknesses. In this work, we run $r$-process calculations for five trajectories using 49 different neutron-capture rate models. Our results shed light on the importance of taking into account shell effects and pairing correlations in the network calculations.

To increase the storage time of ultracold neutrons (UCNs) inside the material traps it is promising to cover the trap walls by liquid ${}^4\mathrm{He}$, a material which does not absorb neutrons at all. The rough side wall of UCN trap holds the required amount of ${}^4\mathrm{He}$ by the capillary effects, but the edges of the wall roughness remain insufficiently coated. Here we propose to apply an electric voltage to these rough side walls of UCN traps to increases the thickness of liquid He on the wall edges and to cover the entire wall surface by sufficiently thick helium films. This completely protects UCNs from being absorbed inside the trap walls. We estimate the required electric field and voltage for several possible designs of UCN traps. This improvement may give rise to a new generation of ultracold neutron traps with very long storage time. We also estimate the influence of this electric field on the dispersion of ripplons—the quanta surface waves, which give the main contribution to the inelastic UCN scattering at low temperature.

We sample over 500 relativistic mean-field theories constrained by chiral effective-field theory and properties of isospin-symmetric nuclear matter and test them against known stellar structure constraints. This includes a recent mass and radius measurement of a compact object in supernova remnant HESS J1731-347, with an unusually low mass of $M=0.{77}_{-0.17}^{+0.20}{M}_{\odot }$ and a compact radius of $R=10.4_{-0.78}^{+0.86}$ km. We show that none of the sampled nuclear models meet all constraints at the $68\%$ credibility level, but that hybrid equations of state with a quark-matter inner core and nuclear outer core easily can. This indicates a tension between astrophysical constraints and low-energy nuclear theory.

Our previous investigation of neutron-star crusts, based on the functional BSk24, led to a substantial reduction of the pasta mantle when Strutinsky integral and pairing corrections were added on top of the fourth-order extended Thomas-Fermi (ETF) method. Here, our earlier calculations are widened to a larger set of functionals within the same family and we find that the microscopic corrections weaken significantly the influence of the symmetry energy. In particular, the correlation observed at the pure ETF level between the density for the onset of pasta formation and the symmetry energy vanishes, not only for the $L$ coefficient but also for the symmetry-energy values at the relevant densities. Moreover, the inclusion of microscopic corrections results in a much lower abundance of pasta for all functionals.

We brought to light the primordial importance and relevance of the neck-formation/neck-length parameter defined within the two center shell model, especially for the synthesis of new superheavy elements. We have implemented the quantum mechanical fragmentation theory in the dynamical cluster-decay model for the decay of a hot and rotating compound nuclear system. This theory provides a central idea to understanding the nucleus-nucleus collisions and the subsequent decay processes together such as fission and evaporation residue, etc. Our recently published result in the case of $Z=116$ and 118 has became a thrust of this work; we have successfully predicted the practical range of the cross sections of decay channels without tracing the experimental data. Henceforth, we can show that the neck-length parameter has a genuine power to predict the approximate cross section values for unknown decay channels. Such calculations may be useful for guiding experimentalists to choose adequate systems for the production of future superheavy elements

Lifetimes of the low-lying yrast states $2^{+}$, $4^{+}$, and $6^{+}$ of the unstable nucleus ${}^{182}\mathrm{Os}$ were measured using digital fast-timing techniques. The lifetimes of the $4^{+}$ and $6^{+}$ states were determined for the first time. The remeasured value for the lifetime of the $2_1^{+}$ state was taken into account to evaluate the discrepancy between two inconsistent literature values. The lifetimes and extracted $B\left(E2\right)$ values are presented and discussed in terms of collective signatures and transitional phenomena. The $B(E2;4_1^{+}\to 2_1^{+})/B(E2;2_1^{+}\to 0_1^{+})$ ratio of 1.39(7) supports the interpretation of ${}^{182}\mathrm{Os}$ as a rigid rotor. This value is discussed in the context of these of the neighboring isotopes and isotones and calculations in the framework of the interacting boson model 1. Additionally, competing influences from the near lying collective deformed region, $\gamma$-soft rotors, X(5) symmetry, and neighboring regions of shape coexistence in low excitation states are assumed to influence the structure of the nucleus of interest: The trend of the excitation energies of the $\gamma$- and $K^{\pi }=0$–bands in the osmium isotopic chain change remarkably at ${}^{182}\mathrm{Os}$. This consideration helps to us delimit and understand the structural transitions in the isotopic and isotonic chains that intersect at ${}^{182}\mathrm{Os}$.

Radioactive dynamics of unstable nuclei are subject to nuclear deformation. The experimentally identified cluster radioactivities in the trans-lead region are reexamined using an improved density-dependent cluster model in this work, where the role of deformation is fully taken into account. Especially, the effects of nuclear diffuseness polarization [Phys. Rev. C 88, 064327 (2013)], a nontrivial distortion of the nuclear surface due to deformation, are further investigated in the calculations of cluster radioactivity as well. In the present work, we generalize a new unified form of deformation-dependent diffuseness in the nuclear density distribution by introducing an adjustable parameter, whose sign determines the specific surface polarization mode, while its amplitude together with the deformation parameters handle the surface polarization degree of a deformed nucleus. Within this diffuseness correction, we first examine the improved model's capability of investigating the properties of cluster radioactivity. The experimental half-lives are found to be well reproduced with a factor of $\approx 3$. Sequentially we consider three different surface polarization modes for the emitted cluster in the calculations and compare their impacts on the properties of cluster radioactivity. Distinct features and effects of these three surface polarization modes are presented in detail. As a result, it is found that the three different surface polarization modes may alter the geometry of daughter-cluster interactions, leading to a fluctuation of the cluster radioactivity half-lives. It is expected this work can serve as a helpful reference for both the experimental and theoretical studies of nuclear structures in the future.

Heavy-flavor jets are powerful tools to gain insight into the in-medium partonic energy-loss mechanisms and the quark-gluon plasma's (QGP) transport properties in high-energy nuclear collisions. In this work we present the first theoretical study of the longitudinal momentum fraction $z_{\left|\right|}$ carried by heavy-flavor mesons in jets in $\mathrm{Pb}+\mathrm{Pb}$ collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$. The $\mathrm{p}+\mathrm{p}$ baseline is provided by powheg$+\mathrm{p}$ythia8, which matches the next-to-leading-order hard processes with the parton shower. We employ a Monte Carlo transport model, which considers the collisional and radiative partonic energy loss, to simulate the evolution of heavy-flavor jets in the expanding QGP medium. We observe steeper $z_{\left|\right|}$ distributions of ${\mathrm{B}}^0$ jets compared to those of ${\mathrm{D}}^0$ jets at the same kinematics region in $\mathrm{p}+\mathrm{p}$ collisions, which may be a hint of the harder jet fragmentation function of b jets compared to c jets in vacuum. In $\mathrm{A}+\mathrm{A}$ collisions, it is shown that the jet quenching effect would generally decrease the values of $z_{\left|\right|}$. We have made a systematical study on how several factors, including jet $p_{\mathrm{T}}$, jet radius $R$, and collision centrality, would influence the medium modification of $z_{\left|\right|}$ distributions of a ${\mathrm{D}}^0$ jet. In addition, we predict visibly stronger nuclear modifications of ${\mathrm{B}}^0$-jet $z_{\left|\right|}$ distributions compared to a ${\mathrm{D}}^0$ jet within the same $p_{\mathrm{T}}$ windows as a result of the much steeper initial $z_{\left|\right|}$ distribution of the ${\mathrm{B}}^0$ jet in vacuum.

Measurements of the suppression and correlations of dijets is performed using $3\mu {\mathrm{b}}^{-1}$ of Xe+Xe data at $\sqrt{s_{NN}}=5.44$ TeV collected with the ATLAS detector at the CERN Large Hadron Collider. Dijets with jets reconstructed using the $R=0.4$ anti-$k_t$ algorithm are measured differentially in jet $p_{\text{T}}$ over the range of 32 to 398 GeV and the centrality of the collisions. Significant dijet momentum imbalance is found in the most central Xe+Xe collisions, which decreases in more peripheral collisions. Results from the measurement of per-pair normalized and absolutely normalized dijet $p_{\text{T}}$ balance are compared with previous $\mathrm{Pb}+\mathrm{Pb}$ measurements at $\sqrt{s_{NN}}=5.02$ TeV. The differences between the dijet suppression in Xe+Xe and $\mathrm{Pb}+\mathrm{Pb}$ are further quantified by the ratio of pair nuclear-modification factors. The results are found to be consistent with those measured in $\mathrm{Pb}+\mathrm{Pb}$ data when compared in classes of the same event activity and when taking into account the difference between the center-of-mass energies of the initial parton scattering process in Xe+Xe and $\mathrm{Pb}+\mathrm{Pb}$ collisions. These results should provide input for a better understanding of the role of energy density, system size, path length, and fluctuations in the parton energy loss.

Excited levels in ${}^{92}\mathrm{Kr}$, ${}^{96}\mathrm{Zr}$, and ${}^{98}\mathrm{Mo}$ nuclei were reinvestigated using high-statistics multiple-$\gamma$ coincidence data measured with the EXILL and FIPPS Ge arrays, following neutron-induced fission of ${}^{235}\mathrm{U}$ and neutron capture on a ${}^{97}\mathrm{Mo}$ target, respectively. The experimental goal was to search for new levels, especially with low spins, as well as to firm up spin-parity assignments to known levels. In total of 16 new levels with 64 new or corrected decays and 35 new or improved spin-parity assignments were observed in the three nuclei. We also performed large-scale shell-model calculations to learn more about the microscopic structure of levels in these nuclei. The evolution of collectivity in $N=56$ isotones is discussed, stressing the important role of various single-particle excitations, in particular of the $\pi g_{9/2}$ orbital, in the shape evolution in the region.