This study employs the isospin-dependent Boltzmann-Uehling-Uhlenbeck model to simulate intermediate-energy heavy-ion collisions between prolate nuclei ${}^{24}\mathrm{Mg}$. The emphasis is on investigating the influence of centrality and orientation in several collision scenarios. The final-state particle multiplicities and anisotropic flows are primarily determined by the eccentricity and the area of the initial overlap. This not only provides feedback on the collision systems, but also, to some extent, provides a means to explore the fine structure inside deformed nuclei. Additionally, nonpolarized collisions are further discussed. These results contribute to the understanding of the geometric effects in nuclear reactions, and aid in the exploration of other information on reaction systems, such as the equation of state and nuclear high-momentum tail.

Evidence for a flavor asymmetry between the $\overline{u}$ and $\overline{d}$ quark distributions in the proton has been found in deep-inelastic scattering and Drell-Yan experiments. The pronounced dependence of this flavor asymmetry on $x$ (fraction of nucleon momentum carried by partons) observed in the Fermilab E866 Drell-Yan experiment suggested a drop of the $\overline{d}\left(x\right)/\overline{u}\left(x\right)$ ratio in the $x>0.15$ region. We report results from the SeaQuest Fermilab E906 experiment with improved statistical precision for $\overline{d}\left(x\right)/\overline{u}\left(x\right)$ in the large $x$ region up to $x=0.45$ using the 120 GeV proton beam. Two different methods for extracting the Drell-Yan cross section ratios, ${\sigma }^{pd}/2{\sigma }^{pp}$, from the SeaQuest data give consistent results. The $\overline{d}\left(x\right)/\overline{u}\left(x\right)$ ratios and the $\overline{d}\left(x\right)-\overline{u}\left(x\right)$ differences are deduced from these cross section ratios for $0.13<x<0.45$. The SeaQuest and E866/NuSea $\overline{d}\left(x\right)/\overline{u}\left(x\right)$ ratios are in good agreement for the $x\lesssim 0.25$ region. The new SeaQuest data, however, show that $\overline{d}\left(x\right)$ continues to be greater than $\overline{u}\left(x\right)$ up to the highest $x$ value ($x=0.45$). The new results on $\overline{d}\left(x\right)/\overline{u}\left(x\right)$ and $\overline{d}\left(x\right)-\overline{u}\left(x\right)$ are compared with various parton distribution functions and theoretical calculations.

In nuclear astrophysics, ${}^{141}\mathrm{Pr}$ is mainly produced by an $s$ process, which has a neutron magic number $(N=82)$ leading to its low capture cross section and strongly affecting the $s$ process. Its neutron capture cross section is an important input parameter for nuclear astrophysical network calculations. According to the EXFOR database, the measurement precision for the ${}^{141}\mathrm{Pr}(n,\gamma )$ cross section should be improved in the resolved and unresolved resonance region. The $(n,\gamma )$ cross section of ${}^{141}\mathrm{Pr}$ was measured between 1 eV and 500 keV at the Back-n facility of the Chinese Spallation Neutron Source using the time-of-flight (TOF) method. The prompt $\gamma$ rays were detected by four ${\mathrm{C}}_6{\mathrm{D}}_6$ liquid scintillator detectors, and the data was analyzed using the pulse-height weighting technique (PHWT). The majority of results are in agreement with the evaluated data libraries ENDF/B-VIII.0, JENDL-5.0, and TENDL-2021, with some significant exceptions for small resonances. The multilevel $R$-matrix Bayesian code sammy was used to extract the resonance parameters of ${}^{141}\mathrm{Pr}$ in the resolved resonance region. And the Maxwell average cross section (MACS) from $kT=5$ to 100 keV is calculated in the temperature range of the $s$-process nucleosynthesis model. In particular, at $kT=30$ keV the MACS value of ${}^{141}\mathrm{Pr}$ is $145.0\pm 13.7$ mb, which shows an obvious discrepancy with the Karlsruhe Astrophysical Database of Nucleosynthesis in Stars (KADoNiS) recommended value $111.4\pm 1.4$ mb.

Nuclei in the vicinity of driplines have been receiving a lot of attention in nuclear structure studies. In the nuclei, the continuum coupling is crucial in reproducing weakly bound and unbound phenomena. To calculate observables of the nuclei as open quantum systems, we have developed valence-space effective operators in the complex-energy Berggren basis using many-body perturbation theory. We focus on the Gamow-Teller $\beta$ decay in the $\mathit{sd}$ shell. The two- plus three-nucleon force from the chiral effective field theory, named EM1.8/2.0, has been used. The Gamow shell model which takes the continuum coupling into account can properly reproduce experimental observations of weakly bound and unbound states. The $\beta$-decay isospin asymmetry between the dripline nucleus ${}^{22}\mathrm{Si}$ and its mirror partner ${}^{22}\mathrm{O}$ is reproduced, in which the $s_{1/2}$ continuum plays a key role. Significant Thomas-Ehrman shift is seen through mirror energy differences between the mirror daughters ${}^{22}\mathrm{Al}$ and ${}^{22}\mathrm{F}$, in which the continuum effect plays an important role.

Background: The appearance of isomeric states in neutron-rich nuclei can provide a wealth of information on the underlying nuclear configurations as a progression is made from stable to exotic nuclei. These states can be characterized by measuring the half-lives and transition probabilities associated with their deexcitations. Recent studies on neutron-rich Si isotopes near $N=20$ and approaching $N=28$ have revealed states with intruder configurations resulting from multiple-particle, multiple-hole excitations across the closed shell gaps. These intruder states appear at low excitation energies along the Si isotopic chain, pointing to a diminished shell gap at $N=28$.

Purpose: The experiment was set up to directly measure the half-lives of isomeric states in neutron-rich nuclei populated via $\beta$ decay.

Methods: ${}^{37}\mathrm{Al}$ and ${}^{38}\mathrm{Al}$ isotopes were produced in the projectile fragmentation reaction of a ${}^{48}\mathrm{Ca}$ primary beam at NSCL. The isotopes were implanted into a ${\mathrm{CeBr}}_3$ detector, populating excited states of interest in ${}^{37}\mathrm{Si}$ following their ${\beta }^{-}$ and ${\beta }^{-}\mathrm{n}$ decay, respectively. Ancillary arrays of HPGe and ${\mathrm{LaBr}}_3\left(\mathrm{Ce}\right)$ detectors were used to detect $\beta$-delayed $\gamma$ rays. The half-lives of populated isomeric states were measured using the $\beta -\gamma$ timing method.

Results: The half-life of the 68-keV $(7/2_1^{-})$ state in ${}^{37}\mathrm{Si}$ was measured for the first time as 9.1(7) ns, while that of the 156-keV $(3/2_1^{-})$ state was 3.20(4) ns, consistent with a previously reported value. The reduced transition probabilities and transition matrix elements associated with the $\gamma$-ray decay from these excited states to the $(5/2_1^{-})$ ground state were extracted and agree with results from shell model calculations.

Conclusions: The characterization of the $(7/2_1^{-})$ and $(3/2_1^{-})$ states in ${}^{37}\mathrm{Si}$ validates shell model predictions of low-lying nanosecond isomers in neutron-rich odd-$A$ Si isotopes approaching the $N=28$ shell gap.

Background: $\beta$-decay half-life is sensitive to the shell structure near the Fermi levels. Nuclear deformation thus impacts the $\beta$-decay properties.

Purpose: A first-order shape-phase transition in neutron-rich Zr isotopes is predicted by some models. We investigate the $\beta$-decay half-lives of neutron-rich nuclei around ${}^{110}\mathrm{Zr}$, where the shape-phase transition is predicted to occur, to see if the $\beta$-decay half-life can be an indicator of the shape changes.

Method: The proton-neutron quasiparticle random-phase approximation (RPA) is adopted to calculate the Gamow-Teller transitions. In addition, we apply the quasiparticle-vibration coupling (PVC) to consider the phonon couplings.

Results: The spherical and oblate configurations give similar half-lives but shorter ones than the prolate configuration at the RPA level. The PVC effect further reduces the half-lives in general, but the effect is smaller for the deformed configuration than that for the spherical one. As a result, it makes the shape change from the oblate configuration to the spherical configuration visible. Therefore, a sudden shortening of $\beta$-decay half-lives is always found at the nuclear shape changes.

Conclusions: $\beta$-decay half-life is an indicator of the shape-phase transition. The shape mixing and the roles of the triaxial deformation are subject to study in the future.

Metal tubes plated with nickel-phosphorus are used in many fundamental physics experiments that use ultracold neutrons (UCN) because of their ease of fabrication. These tubes are usually polished to an average roughness of $25\text{–}150\mathrm{nm}$. However, there is no scattering model that accurately describes UCN scattering on such a rough guide surface with a mean-square roughness greater than $5\mathrm{nm}$. We, therefore, developed a scattering model for UCN in which scattering from random surface waviness with a size larger than the UCN wavelength is described by a microfacet Bidirectional Reflectance Distribution Function model (mf-BRDF model), and scattering from smaller structures by the Lambert's cosine law (Lambert model). For the surface waviness, we used the statistical distribution of surface slope measured by an atomic force microscope on a sample piece of guide tube as an input of the model. This model was used to describe UCN transmission experiments conducted at the pulsed UCN source in J-PARC. In these experiments, a UCN beam collimated to a divergence angle smaller than $\pm 6^{\circ }$ was directed into a guide tube with a mean-square roughness of 6.4 to $17\mathrm{nm}$ at an oblique angle, and the UCN transport performance and its time-of-flight distribution were measured while changing the angle of incidence. The mf-BRDF model combined with the Lambert model with scattering probability $p_L=0.039\pm 0.003$ reproduced the experimental results well. We have thus established a procedure to evaluate the characteristics of UCN guide tubes with a surface roughness of approximately $10\mathrm{nm}$.

This paper investigates the impacts of the different surface energy coefficients on the compound nucleus decay modes during heavy ion fusion reactions, with focus given to the superheavy nuclei (SHN) in the range of $Z=112$–118. The evaporation-residue (ER) cross sections were calculated for different surface asymmetric constants, $k_s$ and surface energy constants, ${\gamma }_0$. In these calculations, the dinuclear system model and proximity potential, along with considering deformed nuclei, were employed. Comparing the experimental data and this theoretical approach, the best values of $k_s$ and ${\gamma }_0$ are 0.7546 and $0.9180\mathrm{MeV}{\mathrm{fm}}^{-2}$, respectively. Furthermore, this new model was used to investigate the probability of synthesis of experimentally unknown heavier systems with $Z=119$ and 120. There exist five promising combinations to synthesize SHN with $Z=119$: (a) $\mathrm{Cf}(\mathrm{Sc},3n){}^{291}119$ with the ER cross section, ${\sigma }_{3n}=417.1\mathrm{fb}$ at the incident energy $E_{\mathrm{c}.\mathrm{m}.}=219\mathrm{MeV}(E^{*}=39.84\mathrm{MeV})$, (b) $\mathrm{Cf}(\mathrm{Sc},4n){}^{290}119$ with the ER cross section, ${\sigma }_{4n}=138.5\mathrm{fb}$ at the incident energy $E_{\mathrm{c}.\mathrm{m}.}=221\mathrm{MeV}(E^{*}=41.84\mathrm{MeV})$, (c) ${}^{247}\mathrm{Bk}(\mathrm{Ti},3n){}^{294}119$ with the ER cross section, ${\sigma }_{3n}=11.2\mathrm{fb}$ at the incident energy $E_{\mathrm{c}.\mathrm{m}.}=226\mathrm{MeV}(E^{*}=35.15\mathrm{MeV})$, (d) $\mathrm{Es}(\mathrm{Ca},3n){}^{299}119$ with the ER cross section, ${\sigma }_{3n}=9115.15\mathrm{fb}$ at the incident energies $E_{\mathrm{c}.\mathrm{m}.}=208\mathrm{MeV}(E^{*}=32.14\mathrm{MeV})$, and e) $\mathrm{Es}(\mathrm{Ca},4n){}^{298}119$ with the ER cross section, ${\sigma }_{4n}=735.46\mathrm{fb}$ at the incident energies $E_{c.m.}=210\mathrm{MeV}(E^{*}=34.14\mathrm{MeV})$. In addition, it is found that the best combinations to synthesize SHN with $Z=120$ are $\mathrm{Cf}(\mathrm{Ti},3n){}^{296}120$ with the ER cross section, ${\sigma }_{3n}=51.19\mathrm{fb}$ at the incident energy $E_{\mathrm{c}.\mathrm{m}.}=228\mathrm{MeV}(E^{*}=33.19\mathrm{MeV})$, and $\mathrm{Cf}(\mathrm{Ti},3n){}^{298}120$ with the ER cross section, ${\sigma }_{3n}=43.17\mathrm{fb}$ at the incident energy $E_{\mathrm{c}.\mathrm{m}.}=227\mathrm{MeV}(E^{*}=33.82\mathrm{MeV})$.

We employ the Boltzmann transport model to study the charmonium regeneration with nonthermal charm quarks in relativistic heavy-ion collisions. As heavy quarks do not reach kinetic thermalization in the quark-gluon plasma (QGP), the final transverse momentum distribution of regenerated charmonium depends on the degree of charm quark kinetic thermalization. When the charm momentum distribution becomes harder, more charm quarks are distributed in the middle ($3<p_T<6$ $\text{GeV}\text{/}c$) and high ($p_T\ge 6$ $\text{GeV/}c$) $p_T$, where the production of regenerated charmonium also becomes larger. In this work, we explore the degree of charm quark kinetic thermalization qualitatively and its effect on the charmonium distribution. With nonthermal momentum distribution of charm quarks in the coalescence process, the nuclear modification factor $R_{AA}\left(p_T\right)$ of charmonium enhances at middle $p_T$. Besides, the elliptic flow $v_2\left(p_T\right)$ of charmonium also enhances at middle $p_T$ as more regenerated charmonium are distributed in this $p_T$ region. The theoretical calculations with nonthermal charm distribution explain well the $p_T$ dependence of charmonium $R_{AA}$ and $v_2$, which indicates that charm quarks do not reach complete kinetic thermalization in the QGP when charmonium are regenerated.

The nuclear dependence of the inclusive inelastic electron scattering cross section (the EMC effect) has been measured for the first time in ${}^{10}\mathrm{B}$ and ${}^{11}\mathrm{B}$. Previous measurements of the EMC effect in $A\le 12$ nuclei showed an unexpected nuclear dependence; ${}^{10}\mathrm{B}$ and ${}^{11}\mathrm{B}$ were measured to explore the EMC effect in this region in more detail. Results are presented for ${}^9\mathrm{Be}$, ${}^{10}\mathrm{B}$, ${}^{11}\mathrm{B}$, and ${}^{12}\mathrm{C}$ at an incident beam energy of 10.6 GeV. The EMC effect in the boron isotopes was found to be similar to that for ${}^9\mathrm{Be}$ and ${}^{12}\mathrm{C}$, yielding almost no nuclear dependence in the EMC effect in the range $A=4\text{–}12$. This represents important new data supporting the hypothesis that the EMC effect depends primarily on the local nuclear environment due to the cluster structure of these nuclei.

The nuclear symmetry energy and its behavior with density has been recently evaluated with enhanced value by PREX-2 experiment. This new values enables direct Urca neutrino emission process to be functioning in the dense matter inside neutron stars. With this new outlook we study the cooling rate of canonical mass neutron stars and compare with available observational cooling data. We find most of the isolated neutron star thermal profile is compatible with the cooling of canonical mass star including superfluidity suppression.

We have analyzed the systematics of $b$ and $c$ coefficients of the quadratic isobaric multiplet mass equation (IMME) using the newly measured masses of the upper $fp$-shell nuclei in the experimental cooler storage ring (CSRe) in Lanzhou. The $c$ coefficient for the $A=70$, $T=1$ isospin multiplet is found to be negative, which is severely deviating from overall systematics and in conflict with theoretical expectations of the isospin symmetry. This anomaly is analyzed and attributed to the presently adopted mass of ${}^{70}\mathrm{Br}$ in the latest Atomic Mass Evaluation (AME2020). Under the assumption of a smooth variation of Coulomb energy differences with changing mass number $A$, the ground-state mass excess of ${}^{70}\mathrm{Br}$ is deduced to be $-51934\left(16\right)$ keV, which is 508(22) keV more bound than the adopted value. Using this mass value, the calculated $c$ coefficient of IMME at $A=70$ fits well into the systematics, and the obtained corrected $Ft$ value for the $0^{+}\to 0^{+}$ superallowed $\beta$ decay of ${}^{70}\mathrm{Br}$ is consistent with the world-average value.

The spin cutoff parameter for ${}^{59}\mathrm{Ni}$ has been studied from different types of experimental data including neutron angular distributions from the ${}^{56}\mathrm{Fe}(\alpha ,n){}^{59}\mathrm{Ni}$ reaction, spin of discrete levels, the level density from the proton evaporation spectrum of the ${}^{54}\mathrm{Fe}({}^6\mathrm{Li},p){}^{59}\mathrm{Ni}$ reaction and neutron resonance spacing. Experimental data points were compared with calculations using models widely used in literature. It was found that the available empirical models overestimate data points in the energy region below the neutron separation energy, while microscopic calculations which take into account pairing correlations within Hartree-Fock $+$ Bardeen-Cooper-Schrieffer approach are consistent with data. It confirmed earlier findings that pairing correlations play an important role and need to be taken into account when the spin cutoff parameter is calculated below the neutron separation energy.

The $\alpha$ decay of the neutron-deficient ${}^{190}\mathrm{At}$ isotope was observed following the ${}^{103}\mathrm{Rh}({}^{90}\mathrm{Zr},3n){}^{190}\mathrm{At}$ reaction at Argonne National Laboratory. The reaction products were separated from the beam using the Argonne Gas-Filled Analyzer and implanted into a double-sided Si strip detector. The spatial and temporal correlations between implanted nuclei and subsequent $\alpha$ decays towards the known daughter isotope ${}^{186}\mathrm{Bi}$ were used to identify and characterize ${}^{190}\mathrm{At}$ nuclei. Two possible decay scenarios are proposed for the ${}^{190}\mathrm{At}\to {}^{186}\mathrm{Bi}$ decay.

The low-lying structure of ${}^{13}\mathrm{Be}$ has remained an enigma for decades. Despite numerous experimental and theoretical studies, large inconsistencies remain. Being both unbound and one neutron away from ${}^{14}\mathrm{Be}$, the heaviest bound beryllium nucleus, ${}^{13}\mathrm{Be}$ is difficult to study through simple reactions with weak radioactive-ion beams or more complex reactions with stable-ion beams. Here, we present the results of a study using the ${}^{12}\mathrm{Be}(d,p){}^{13}\mathrm{Be}$ reaction in inverse kinematics using a 9.5 MeV per nucleon ${}^{12}\mathrm{Be}$ beam from the ISAC-II facility. The solid deuteron target of IRIS was used to achieve an increased areal thickness compared to conventional deuterated polyethylene targets. The $Q$-value spectrum below $-4.4$ MeV was analyzed using a Bayesian method with geant4 simulations. A three-point angular distribution with the same $Q$-value gate was fit with a mixture of $s$- and $p$-wave, $s$- and $d$-wave, or pure $p$-wave transfer. The $Q$-value spectrum was also compared with geant simulations obtained using the energies and widths of states reported in four previous works. It was found that our results are incompatible with works that revealed a wide $5/2^{+}$ resonance but shows better agreement with ones that reported a narrower width.

Systematic measurements of 51 isotopic cross sections from fragmentation reactions of 240 MeV/nucleon ${}^{12,14}\mathrm{C}$, ${}^{14,16}\mathrm{N}$, and ${}^{16}\mathrm{O}$ projectiles on a carbon target were performed at the RIBLL2 separator and the external target facility (ETF) of the Heavy-Ion Research Facility in Lanzhou (HIRFL). Our experimental cross sections produced by fragmentation of three stable projectiles, i.e., ${}^{12}\mathrm{C}$, ${}^{14}\mathrm{N}$, and ${}^{16}\mathrm{O}$, were compared with some previous experimental data measured at different energies. The comparison indicates that our experimental data are in generally good agreement with previous experimental data. Tens of new isotopic cross sections produced by fragmentation of two unstable projectiles ${}^{14}\mathrm{C}$ and ${}^{16}\mathrm{N}$ were also measured in this work. All cross sections measured in this work were used for benchmarking three fragmentation models, i.e., ABRABLA, NUCFRG, and FRACS. Most experimental data can be well reproduced by these fragmentation models, but there are severe discrepancies for some isotopic cross sections from fragmentation of unstable projectiles.

Background: The description of deuteron-induced inclusive reactions has been an important subject in direct nuclear reaction studies and nuclear data science. For proton-induced inclusive processes, the semiclassical distorted wave model (SCDW) is one of the most successful models based on quantum mechanics.

Purpose: We improve SCDW for deuteron-induced inclusive processes and clarify the importance of the proper treatment of the kinematics of the deuteron inside a nucleus.

Methods: The double differential cross section (DDX) of the inclusive deuteron-emission process $(d,d^{\prime }x)$ is described by one-step SCDW. The changes in the kinematics due to the distortion effect, the refraction effect, are taken into account by the local semiclassical approximation.

Results: The calculated DDXs of $(d,d^{\prime }x)$ reasonably reproduce experimental data in the small energy-transfer region and at forward and middle angles with some exceptions. The angular distributions of $(d,d^{\prime }x)$ are improved by including the refraction effect.

Conclusion: The proper treatment of the changes in the kinematics of the deuteron inside a nucleus is necessary in describing the ($d,d^{\prime }x$) reaction. The effect of the changes on the DDX of $(d,d^{\prime }x)$ is significant compared to on the proton-induced inclusive process $(p,p^{\prime }x)$ because of the stronger distortion effect on the deuteron.

The availability of high-intensity, heavy-ion beams coupled to sensitive, large solid-angle-acceptance spectrometers has enabled a detailed examination of the fission fragments produced in induced-fission reactions. The abrasion-fission process involves the formation of projectile-like prefragments in violent nuclear collisions at relative energies in excess of 100 MeV/u. At intermediate energies below this threshold, experiments suggest a change in the prefragment kinematic qualities. Information regarding the influence of this transitional phase upon the evolution of nuclei approaching the point of scission is scarce. In this article, data are presented for over 200 nuclei from nickel to palladium produced in abrasion-fission reactions of a 80 MeV/u ${}^{238}\mathrm{U}$ beam. Cross sections were obtained following yield measurements performed for the principal charge states of the identified fission fragments and a detailed analysis of the ion transmission. A full kinematic analysis of the fission fragments has been performed using the LISE${}^{++}$ software package, where the trajectory of an ion passing through a spectrometer can be reconstructed based upon measurements at the focal plane. The results obtained at the S800 spectrograph are compared with predictions obtained with a three-fission progenitor (3EER) model. Systematic studies of fission-fragment properties continue to provide a valuable experimental benchmark for theoretical efforts directed toward describing this complex decay channel, that is important in the context of planning experiments to explore the neutron-rich region of the nuclear chart at rare-isotope beam facilities.

Within the model A in the Hohenberg's dynamical universality classification, we investigate the critical slowing down effects on the critical fluctuations driven by the expanding quark-gluon plasma, using a trajectory and cooling rate obtained from hydrodynamics. We numerically solved the Langevin dynamics of the nonconserved order parameter field and find that, compared with commonly used Hubble-like expansion, the cooling rate of a realistic hydrodynamic system is pretty large and the associated critical slowing down effects strongly suppress the higher-order cumulants of the order parameter field (e.g., $C_4$). Furthermore, for an evolving system that approaches the critical point, such critical slowing down suppression overcomes the enhancement of the critical fluctuations, which indicates that the largest fluctuations of the order parameter field (i.e., $C_2$) do not necessarily associate with the evolving trajectory closest to the critical point.

We study the flow harmonic distribution in collisions of deformed nuclei. To do this, we use the standard Gram-Charlier method to find the higher-order correction to the well-known Bessel-Gaussian distribution. We find that, apart from the necessity of including a shift parameter ${\overline{v}}_n$, the modified flow distribution accurately describes the distribution of flow harmonics in a system formed after collisions of deformed nuclei with quadrupole and octupole deformity. Using the shifted radial distribution arising from this method, we scrutinize the effect of deformation on flow distribution. We also propose a way to measure ${\overline{v}}_2$ in deformed-nucleus collisions.