The hindrance to complete fusion is studied as a function of the charge asymmetry of colliding nuclei and orbital angular momentum of the collision. The formation and evolution of a dinuclear system (DNS) in the heavy-ion collisions at energies near the Coulomb barrier is calculated in the framework of the DNS model. The DNS evolution is considered as nucleon transfer between its fragments. The results prove that a hindrance at formation of a compound nucleus (CN) is related with the quasifission process, which is breakup of the DNS into products instead to reach the equilibrated state of the CN. The role of the angular momentum in the charge (mass) distribution of the reaction products for the given mass asymmetry of the colliding nuclei has been demonstrated. The results of this work have been compared with the measured data for the quasifission yields in the ${}^{12}\mathrm{C}+{}^{204}\mathrm{Pb}$ and ${}^{48}\mathrm{Ca}+{}^{168}\mathrm{Er}$ reactions to show the role of the mass asymmetry of the entrance channel.

Within the possible least uncertainty on the nuclear incompressibility $K_0$, we examine effects of $K_0$ in heavy-ion collisions at intermediate energies. Based on simulations of Au $+$ Au collisions at 400 MeV/nucleon using an isospin- and momentum-dependent transport model, we find that the incompressibility $K_0$ indeed affects significantly the attainable density in central regions, and thus the particle productions and/or distributions at final states, e.g., nucleon rapidity distributions and yields of charged pions. Nevertheless, through examining the free neutron over proton ratios $n/p$, the neutron-proton differential transverse and directed flows as well as the charged pion ratio ${\pi }^{-}/{\pi }^{+}$ and its kinetic energy distribution, we find that these observables are less affected by the uncertainty of $K_0$, but mainly sensitive to the slope of symmetry energy at the saturation density. We also compare and discuss our results with the corresponding data.

The low-lying, low-spin levels of ${}^{74}\mathrm{Ge}$ were studied with the $(n,n^{\prime }\gamma )$ reaction. $\gamma$-ray excitation function measurements were performed at incident neutron energies from 1.6 to 3.8 MeV, and $\gamma$-ray angular distributions were measured at neutron energies of 2.0, 2.6, 3.0, 3.4, and 3.8 MeV. From these measurements, level spins, level lifetimes, $\gamma$-ray branching ratios, and multipole mixing ratios were determined, and a comprehensive level scheme approaching 3 MeV in excitation energy is presented. Low-lying collective band structures are identified, and a comparison of the level characteristics with large-scale shell-model calculations yields excellent agreement.

Magnetic dipole (M1) excitations of magic nuclei ${}^{48}\mathrm{Ca}, {}^{90}\mathrm{Zr}$, and ${}^{132}\mathrm{Sn}$ are investigated by a self-consistent Hartree-Fock (HF) plus subtracted second random-phase approximation (SSRPA) with Skyrme energy density functions (EDFs). We clarify the effects of the mixing of two-particle two-hole (2p-2h) configurations and tensor correlations in SSRPA on the excitation energies and the quenching of the $M1$ strength. It is shown that the 2p-2h configurations shift the $M1$ peak energies downwards by about 1.5 MeV in both ${}^{48}\mathrm{Ca}$ and ${}^{90}\mathrm{Zr}$. In contrast, the tensor correlations move the peaks upwards and improve the description of experimental data. We also show that the 2p-2h configurations largely fragment the $M1$ strength, and reduce the cumulative strengths around the main $M1$ peaks by about 25% and 27% in ${}^{48}\mathrm{Ca}$ and ${}^{90}\mathrm{Zr}$, respectively, compared with those of random-phase approximation (RPA), as an outcome of the combined effect with the tensor force. The $M1$ transitions in ${}^{132}\mathrm{Sn}$ are calculated by the same SSRPA model with the Skyrme EDF including the tensor terms.

Low-lying levels in the odd-mass nucleus ${}^{181}\mathrm{Ta}$ have been populated via nuclear resonance fluorescence using a quasimonoenergetic, linearly polarized photon beam at the High Intensity $\gamma$-ray Source ($\mathrm{HI}\gamma \mathrm{S}$) facility at Duke University. The spin and parity of the levels were determined from the azimuthal intensity asymmetry of resonantly scattered $\gamma$ rays with respect to the polarization plane of the incident photon beam. The electric and magnetic dipole strengths were obtained for excitation energies from 2.2 to 3.2 MeV. The results are discussed in terms of the nuclear scissors mode.

Spectrum-averaged cross-section (SACS) ratio measurement showing reduced uncertainties of measured SACS in two independent fission neutron fields is presented. The used prompt fission neutron fields correspond to the ${}^{252}\mathrm{Cf}$(sf) and ${}^{235}\mathrm{U}(n_{\mathrm{th}},f$) fission neutrons. The employed SACS in the ${}^{235}\mathrm{U}(n_{\mathrm{th}},f$) prompt fission neutron spectrum (PFNS) were measured using three different light water reactors: LR-0 and VR-1 zero power reactors and the LVR-15 10 MWt reactor. The employed SACS in the ${}^{252}\mathrm{Cf}$(sf) prompt fission neutron field were measured using a certified high-flux neutron source. Existing correlations among measured SACS in the two different neutron fields are estimated and used to reduce the uncertainty of measured SACS ratio for IRDFF dosimetry reactions. The derived set of measured SACS ratios with reduced uncertainty extends previous works into the higher-energy fission neutron range up to 20–30 MeV. The SACS ratio in ${}^{252}\mathrm{Cf}$(sf) and ${}^{235}\mathrm{U}(n_{\mathrm{th}},f$) PFNS can be used to probe the high-energy tail of the ${}^{235}\mathrm{U}(n_{\mathrm{th}},f$) fission neutron spectrum as the ${}^{252}\mathrm{Cf}$(sf) reference neutron spectrum is relatively well known. Derived experimental SACS ratio data. featuring low uncertainty are compared to the calculated dosimetry SACS ratio using the IRDFF-II dosimetry cross sections and the ${}^{235}\mathrm{U}(n_{\mathrm{th}},f$) ENDF/B-VII.1, ENDF/B-VIII.0, or JEFF-3.3 PFNS evaluations. The ENDF/B-VIII.0 evaluation of the ${}^{235}\mathrm{U}(n_{\mathrm{th}},f$) PFNS agrees well with derived SACS ratio data within quoted uncertainties. Other libraries predict a significantly lower fraction of ${}^{235}\mathrm{U}(n_{\mathrm{th}},f$) fission neutrons above 11 MeV of the outgoing neutron energy.

This paper presents recent experimental results on the yield of prompt fission $\gamma$ rays from the spontaneous fission of ${}^{252}\mathrm{Cf}$. We use an ionization chamber to tag fission events and measure the masses and kinetic energies of the fission fragments and trans-stilbene organic scintillators to measure the neutrons and $\gamma$ rays emitted by the fission fragments. The combination of the ionization chamber and trans-stilbene scintillators allows us to determine the properties of neutrons and $\gamma$ rays in coincidence with the fragments. The yield of $\gamma$ rays is known to be influenced by the angular momenta (AM) of the fission fragments. We present experimental evidence indicating that the total $\gamma$-ray multiplicity, i.e., the sum of both fragments' emission, saturates at sufficiently high internal fragment excitation energies. We also observe distinct behaviors for the yield of $\gamma$ rays from the light and heavy fragments, which for certain mass and total kinetic energy (TKE) regions are weakly or anticorrelated, indicating the presence of complex AM generation modes. We also observed a mass- and TKE-dependent anisotropy of the $\gamma$ rays, which challenges and expands on the conventional notion that the fragments' AM are always aligned perpendicularly to the fission axis. Moreover, the dependence of the anisotropy on mass and TKE indicates a dependence of these properties on the specific fission channels, thus providing an insight into the deformations and dynamics in fission and their connection with experimentally observable quantities.

The PHENIX experiment has performed a systematic study of identified charged-hadron $({\pi }^{\pm },$ $K^{\pm },$ $p,$ $\overline{p})$ production at midrapidity in $p+\mathrm{Al}$, ${}^3\mathrm{He}+\mathrm{Au}$, and $\mathrm{Cu}+\mathrm{Au}$ collisions at $\sqrt{s_{{}_{NN}}}=200\mathrm{GeV}$ and $\mathrm{U}+\mathrm{U}$ collisions at $\sqrt{s_{{}_{NN}}}=193\mathrm{GeV}$. Identified charged-hadron invariant transverse-momentum $\left(p_T\right)$ and transverse-mass $\left(m_T\right)$ spectra are presented and interpreted in terms of radially expanding thermalized systems. The particle ratios of $K/\pi$ and $p/\pi$ have been measured in different centrality ranges of large ($\mathrm{Cu}+\mathrm{Au}$ and $\mathrm{U}+\mathrm{U}$) and small ($p+\mathrm{Al}$ and ${}^3\mathrm{He}+\mathrm{Au}$) collision systems. The values of $K/\pi$ ratios measured in all considered collision systems were found to be consistent with those measured in $p+p$ collisions. However, the values of $p/\pi$ ratios measured in large collision systems reach the values of $\approx 0.6$, which is a factor of $\approx 2$ larger than in $p+p$ collisions. These results can be qualitatively understood in terms of the baryon enhancement expected from hadronization by recombination. Identified charged-hadron nuclear-modification factors ($R_{AB}$) are also presented. Enhancement of proton $R_{AB}$ values over meson $R_{AB}$ values was observed in central ${}^3\mathrm{He}+\mathrm{Au}$, $\mathrm{Cu}+\mathrm{Au}$, and $\mathrm{U}+\mathrm{U}$ collisions. The proton $R_{AB}$ values measured in the $p+\mathrm{Al}$ collision system were found to be consistent with $R_{AB}$ values of $\varphi$, ${\pi }^{\pm }$, $K^{\pm }$, and ${\pi }^0$ mesons, which may indicate that the size of the system produced in $p+\mathrm{Al}$ collisions is too small for recombination to cause a noticeable increase in proton production.

This paper provides a thorough examination of the $x{F}_3$ structure functions in deep-inelastic scattering through a comprehensive QCD analysis. Our approach harnesses sophisticated mathematical techniques, namely, the Mellin transform combined with Gegenbauer polynomials. We have employed the Jacobi polynomials approach for analysis, conducting investigations at three levels of precision: next-to-leading order (NLO), next-to-next-to-leading order $\left({\mathrm{N}}^2\mathrm{LO}\right)$, and next-next-next-to-leading order $\left({\mathrm{N}}^3\mathrm{LO}\right)$. We have performed a comparison of our sets of valence-quark parton distribution functions with those of recent research groups, specifically CT18 and MSHT20 at NLO and ${\mathrm{N}}^2\mathrm{LO}$, and MSTH23 at ${\mathrm{N}}^3\mathrm{LO}$, which are concurrent with our current analysis. The combination of Mellin transforms with Gegenbauer polynomials proves to be a powerful tool for investigating the $x{F}_3$ structure functions in deep-inelastic scattering and the results obtained from our analysis demonstrate a favorable alignment with experimental data.

Background: $\gamma$-ray spectroscopy studies of the Sn isotopes provide important information on nuclear structure and shell evolution across the long isotopic chain between the doubly-magic ${}^{100}\mathrm{Sn}$ and ${}^{132}\mathrm{Sn}$ nuclei. These studies also offer great value to test and tune nuclear models which can then be applied to other regions of the nuclear chart.

Purpose: We aim to expand the level scheme of ${}^{118}\mathrm{Sn}$ by populating low-spin states in the range of 3–5 MeV and determine their angular momentum for the possible connection of these states to pygmy quadrupole Resonances, a new phenomenon observed in the neighboring ${}^{112,114,124}\mathrm{Sn}$ isotopes as a resonance-like structure in the 3–5 MeV range.

Method: Excited states in ${}^{118}\mathrm{Sn}$ were populated via the ${}^{117}\mathrm{Sn}(n,\gamma ){}^{118}\mathrm{Sn}$ reaction at the Institut Laue-Langevin in Grenoble, France. The FIssion Product Prompt gamma-ray Spectrometer (FIPPS), an array of eight n-type high purity Germanium clover detectors augmented with eight additional clover detectors from IFIN “Horia Hulubei” were used to detect $\gamma$ rays from excited states in ${}^{118}\mathrm{Sn}$. The array provides a superior efficiency for $\gamma$-ray detection and nearly $4\pi$ coverage for the measurements of angular correlations for spin assignment of excited nuclear levels.

Results: Through $\gamma \text{−}\gamma$ coincidences, 112 excited states were identified with 57 being newly placed in the level scheme. From these states, 567 $\gamma$-ray transitions were observed with 501 being newly identified. Many levels were identified in the 3–5 MeV region. Further, an indirect measurement of the $E0$ transition which decays from the $0_3^{+}$ state to the 2p-2h, $0_2^{+}$ state was performed and the $q_K^2(E0/E2)$ and $X(E0/E2)$ for this transition were determined to be 12.7(11) and 6.3(5), respectively. The ${10}^3\times {\rho }^2\left(E0\right)$ was determined to be $>38$ based on a half-life limit of $<200$ ps of the 2057-keV, $0_3^{+}$ level.

Conclusions: The abundant spectroscopic information on ${}^{118}\mathrm{Sn}$ obtained in the present experiment is an important input to the theoretical description of nuclei in the region and highlights the capabilities of the FIPPS array at ILL in conjunction with neutron capture reactions. Many states identified in the 3–5 MeV region could very likely have $J=2^{+}$ and contribute to the pygmy quadrupole resonances.

Simulations of quantum systems in finite volume have proven to be a useful tool for calculating physical observables. Such studies to date have focused primarily on understanding the volume dependence of binding energies, from which it is possible to extract asymptotic properties of the corresponding bound state, as well as on extracting scattering information. For bound states, all properties depend on the size of the finite volume, and for precision studies it is important to understand such effects. In this work, we therefore derive the volume dependence of the mean squared radius of a two-body bound state, using a technique that can be generalized to other static properties in the future. We test our results with explicit numerical examples and demonstrate that we can robustly extract infinite-volume radii from finite-volume simulations in cubic boxes with periodic boundary conditions.

In this paper we explicitly study dominant nucleon-pair configurations in low-lying states of deformed nuclei in two cases; the first is the schematic Elliott's SU(3) model with valence nucleons in the $pf$ shell, and the second is the effective $V_{\mathrm{low}-k}$ interaction with valence protons in the 50-82 shell and valence neutrons in the 82-126 shell, exemplified by ${}^{146}\mathrm{Ba}$ and ${}^{148}\mathrm{Ce}$. We find that the $SD$ nucleon-pair configurations are more predominant in low-lying states of these deformed nuclei than expected. Mixings of nucleon-pair configurations beyond the conventional $SD$-pair subspace, in particular, one-$G$ and/or one-$I$ nucleon-pair configurations, albeit small, are found to be necessary to reproduce the moment of inertia.

Ground state stable nuclei typically have near-spherical geometries but may exhibit exotic shapes and form $\alpha$-particle clusters within their bulk if given excitation energy and/or angular momentum. It is predicted that such clustering can promote the production of angular-momentum stabilized toroidal nuclei. Previous experiment and theory suggest that such states may be evidenced by narrow resonances at high excitation energy in peripheral intermediate energy heavy-ion collisions. There has been recent focus on potential evidence for toroidal states in the $\alpha$-particle disassembly of ${}^{28}\mathrm{Si}$ in collisions of ${}^{28}\mathrm{Si}+{}^{12}\mathrm{C}$ at 35 MeV/nucleon; however, prior evidence is limited by the angular resolution and statistical uncertainties that exist in the measurement. The present work aims to measure the excitation energy distribution for these disassembly events with improved angular resolution and reduced statistical uncertainty using the Forward Array Using Silicon Technology (FAUST). FAUST is equipped with resistive dual-axis duolateral (DADL) position-sensitive silicon detectors capable of submillimeter position resolution. The performance and response of the array was previously characterized in detail to accurately predict the expected resolution of measuring narrow resonances. The measured excitation energy distributions for 7- and 8-$\alpha$ disassembly events showed no strong evidence for highly excited states at the cross section and widths suggested by previous experiment. Further investigation of collision properties that lead to these exit channels revealed challenges in isolating clean projectile-mass decays, where many 7-$\alpha$ events do not originate from a single ${}^{28}\mathrm{Si}$ source. A statistical likelihood analysis was performed to determine the sensitivity of the present measurement for confidently determining resonant yield, providing an upper limit to toroidal high-spin isomer cross section as a function of the excitation energy and width of potential states.

We study the relaxation dynamics of the spin polarization of baryons (nucleon and $\mathrm{\Lambda }$ baryon), in a thermal pion gas as a simple model of the hadronic phase of the QCD plasma produced in relativistic heavy-ion collisions. For this purpose, we formulate the quantum kinetic theory for the spin density matrix of baryons in the leading order of the gradient expansion. Considering the baryon-pion elastic scattering processes as the dominant interaction between baryons and thermal pions, we compute the spin relaxation rate of nucleons and $\mathrm{\Lambda }$ baryons in a pion gas up to temperature 200 MeV. In the case of nucleons, we evaluate the spin relaxation rate in the $s$-channel resonance approximation, based on the known experimental data on $\mathrm{\Delta }$ resonances. We also estimate the spin relaxation rate for $\mathrm{\Lambda }$ baryons, based on experimental inputs and theoretical models for the low-energy $\mathrm{\Lambda }\pi$ scattering, including the chiral perturbation theory.

Flow harmonic coefficients, $v_n$, which are the key to studying the hydrodynamics of the quark-gluon plasma (QGP) created in heavy-ion collisions, have been measured in various collision systems and kinematic regions and using various particle species. The study of flow harmonics in a wide pseudorapidity range is particularly valuable to understand the temperature dependence of the shear viscosity to entropy density ratio of the QGP. This paper presents the first LHCb results of the second- and the third-order flow harmonic coefficients of charged hadrons as a function of transverse momentum in the forward region, corresponding to pseudorapidities between 2.0 and 4.9, using the data collected from PbPb collisions in 2018 at a center-of-mass energy of 5.02 $\text{TeV}$. The coefficients measured using the two-particle angular correlation analysis method are smaller than the central-pseudorapidity measurements at ALICE and ATLAS from the same collision system but share similar features.

In this work we study unitary neutron systems confined in a harmonic-oscillator trap, based on the BCS theory and the quasiparticle ring-diagram method. The low-momentum interaction $V_{\text{low-}k}$ renormalized from a fine-tuned CD-Bonn potential with the ${}^{1}S_0$ scattering length approaching the infinity is adopted. The energy ratios of trapped unitary neutron systems with various particle numbers, both those with magic numbers and those with nonmagic ones, to corresponding noninteracting systems, are shown to all flow to a constant value. The BCS wave functions for these trapped unitary systems, with different trap parameters and different particle numbers, manifest themselves with universal patterns: the effect of harmonic-oscillator shells is significant, and moreover, the orbits of the lowest valence shell are occupied with a uniform probability. We also discuss the self-energy given by the BCS calculation, and present a weighted sum rule satisfied by the monopole components of the unitary neutron-neutron interaction. In terms of these, the constant energy ratio independent of the trap parameter and the particle number can be interpreted.

A systematic analysis of parameters and properties of the Pauli resonance states is performed for light nuclei ${}^6\mathrm{Li}$, ${}^7\mathrm{Li}$, ${}^8\mathrm{Be}$, ${}^9\mathrm{Be}$, and ${}^{10}\mathrm{B}$, which are treated as two-cluster systems. The Pauli resonance states are redundant solutions of the resonating group method. They appear when one tries to use a more advanced description of the internal structure of interacting clusters. Our calculations are performed in the standard and advanced versions of the resonating group method. The standard version employs wave functions of the many-particle oscillator shell model to describe the internal motion of nucleons within each cluster. The advanced version is based on a three-cluster resonating group method. As in the standard version, the internal wave functions of three clusters are approximated by wave functions of the many-particle oscillator shell model. However, in the advanced version, a pair of clusters can form a bound state and then the third cluster is considered to interact with such two clusters, being in such the bound state. It is found that the Pauli resonance states in nuclei under consideration are observed at energies between 11 and 46 MeV, and their widths vary from 8 keV to 6.7 MeV. The analysis of the wave functions of Pauli resonance states and matrix elements of the norm kernel allowed us to formulate an effective method for eliminating Pauli resonance states. It is demonstrated that this method effectively eliminates all determined the Pauli resonance states.

We investigate theoretically a nonrelativistic trace anomaly and its impact on the low-temperature equation of state in spatially one-dimensional three-component fermionic systems with a three-body interaction, which exhibit a nontrivial three-body crossover from a bound trimer gas to dense fermionic matter with increasing density. By applying the $G$-matrix approach to the three-body interaction, we obtain the analytical expression for the ground-state equation of state relevant to the high-density degenerate regime and thereby address how the three-body contact or, equivalently, the trace anomaly emerges. The analytical results are compared with the recent quantum Monte Carlo data. Our study of the trace anomaly and the sound speed could have some relevance to the physics of hadron-quark crossover in compact stars.