Structure function data provide insight into the nucleon quark distribution. They are relatively straightforward to extract from the world's vast, and growing, amount of inclusive leptoproduction data. In turn, structure functions can be used to model the physical processes needed for planning and optimizing future experiments. In this paper a machine learning algorithm capable of predicting, using a unique set of parameters, the $F_2$ structure function, for four-momentum transfer $0.055\le Q^2\le 800.0{\mathrm{GeV}}^2$ and for Bjorken $x$ from $2.8\times {10}^{-5}$ to the pion threshold, is presented. The model was trained and reproduces the hydrogen and the deuterium data at a level comparable with the average uncertainty of the experimental data. Extending the model to heavier nuclei or expanding the kinematic range is straightforward. The model is at least ten times faster than existing grid-based structure functions parametrizations that rely on interpolation and a hundred times faster than models requiring convolutions, making it an ideal candidate for event generators and systematic studies.

Neutron scattering cross sections and angular distributions represent one of the most glaring sources of uncertainty in calculations of nuclear systems. Even simple nuclei like ${}^{12}\mathrm{C}$ show indications of errors in nuclear databases for scattering reactions. Measurements of inelastic neutron scattering have historically measured either the scattered neutrons or the nuclear deexcitation $\gamma$ emission. Only a very small number of experiments attempted correlated measurements of both the neutron and $\gamma$ data simultaneously, even though these $n\text{−}\gamma$ correlations could be essential for understanding particle transport in nuclear systems. In this work we describe a measurement of the $n, \gamma$, and correlated $n\text{−}\gamma$ angular distributions from the $Q=4.4398 \mathrm{MeV}$ ${}^{12}\mathrm{C}(n,n^{\prime }\gamma )$ reaction in a single experiment using an EJ-309 liquid scintillator detector array with wide angular coverage, and with a continuous incident neutron energy range from 6.5 to 16.5 MeV. We also provide a thorough covariance description of these results, including normalization of the probability distribution. While the measured $n$ distributions agree well with the relatively large number of available literature measurements, there are comparatively very few measurements of the $\gamma$ distributions from this reaction. However, our data support the presence of a nonzero $a_4$ Legendre polynomial component of the $\gamma$ angular distribution suggested in past measurements, which is currently not incorporated in the ENDF/B-VIII.0 library despite the use of these same literature data for evaluation of the ${}^{12}\mathrm{C}(n,n^{\prime }\gamma )$ cross section. The correlated $n\text{−}\gamma$ distribution measurements are limited to three measurements at incident neutron energies near 14 MeV. Our results do not generally agree with any of these literature measurements. We observe clear indications of significant changes in the $n$ distribution for specific $\gamma$-detection angles and vice versa especially near thresholds for other reaction channels, which shows the potential for significant bias in experiments that, for example, tag on inelastic scattering using a single or small number of $\gamma$-detection angles and could impact particle transport calculations.

High spin states of the neutron-rich ${}^{104}\mathrm{Mo}$ nucleus have been reinvestigated by analyzing the $\gamma$ rays in the spontaneous fission of ${}^{252}\mathrm{Cf}$ with Gammasphere. Both $\gamma \text{−}\gamma \text{−}\gamma$ and $\gamma \text{−}\gamma \text{−}\gamma \text{−}\gamma$ coincidence data were analyzed. A new $\mathrm{\Delta }I=1$ band has been discovered with a tentative $5^{-}$ band head, and is proposed to form a class of chiral vibrational doublets with another $4^{-}$ band previously found. Angular correlation measurements have been performed to determine the spins and parities. A new $3^{-}$ level has been added to one of the chiral doublet bands in ${}^{106}\mathrm{Mo}$. The origin of the chiral doublet bands in ${}^{104,106}\mathrm{Mo}$ is interpreted as a neutron $h_{11/2}$ particle and mixed $d_{5/2}, g_{7/2}$ hole coupled to the short and long axis, respectively. Triaxial projected shell model calculations have been performed for the chiral doublet bands in ${}^{104,106}\mathrm{Mo}$. The results show reasonably good agreement with the experimental data.

The angular momentum projection (AMP) method is implemented in the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) with the point-coupling density functional. The wave functions of angular momentum projected states are expanded in terms of the Dirac Woods-Saxon (WS) basis, providing a proper description of the asymptotic behavior of the wave functions. The contribution of continuum induced by the pairing is considered by treating the pairing correlation with the Bogoliubov transformation. We present the formulas and numerical checks for the DRHBc$+$AMP approach in detail and use it to study low-lying excited states of axially deformed nuclei. Our calculations show that neutron-rich magnesium isotopes ${}^{36,38,40}\mathrm{Mg}$ are all well-deformed nuclei. The low-lying spectra of these three nuclei are obtained. The ground-state rotational bands of ${}^{36,38,40}\mathrm{Mg}$ are reproduced reasonably well by using this new DRHBc$+$AMP approach with the density functional PC-F1.

In this paper, we systematically calculate the $\alpha$-cluster preformation factors and decay half-lives of light nuclei around two newly observed self-conjugate emitters ${}^{108}\mathrm{Xe}$ and ${}^{104}\mathrm{Te}$. The cluster-formation model is employed to calculate the preformation factors by using the experimental nuclear binding energies obtained from the recently updated atomic mass evaluation (AME2020). The binding energies calculated by the improved Weizsäcker-Skyrme formula (WS4) are also used to evaluate the preformation factors. The typical behaviors are obtained that the preformation factors of even-even nuclei are larger than those of odd-$A$ (even-odd and odd-even) nuclei and the latter are generally larger than those of odd-odd nuclei. Besides, due to Pauli blocking, the preformation factors for isotopic chains are decreased with the increasing neutron number. However, it is found that, as a result of the competition between the Pauli blocking and Coulomb repulsion effects for isotonic chains, the preformation factors are generally increased with the increasing proton number. Moreover, with these obtained preformation factors, the $\alpha$-decay half-lives of these light emitters are further calculated under the density-dependent cluster model. The calculated results are compared with experimental data, especially for the two newly observed emitters.

We study collective modes in anisotropic plasmas of quarks and gluons using a quasiparticle picture and a hard-loop approximation. We use a general class of anisotropic distribution functions, and we consider chirally asymmetric systems. We introduce a complete tensor basis to decompose the gluon polarization tensor into a set of nine scalar functions. We derive and solve the corresponding dispersion equations. Imaginary modes are particularly important because of their potential influence on plasma dynamics. We explore in detail their dependence on the chiral chemical potential and the parameters that characterize the anisotropy of the system. We show that our generalized distributions produce dispersion relations that are much richer in structure than those obtained with a simple one-parameter deformation of an isotropic distribution. In addition, the size and domain of the imaginary solutions are enhanced, relative to those obtained with a one-parameter deformation. Finally, we show that the influence of even a very small chiral chemical potential is significantly magnified when anisotropy is present.

Using the new results on coherent elastic neutrino-nucleus scattering data in cesium-iodide provided by the COHERENT experiment, we determine a new measurement of the average neutron rms radius of ${}^{133}\mathrm{Cs}$ and ${}^{127}\mathrm{I}$. In combination with the atomic parity violation (APV) experimental result, we derive the most precise measurement of the neutron rms radii of ${}^{133}\mathrm{Cs}$ and ${}^{127}\mathrm{I}$, disentangling for the first time the contributions of the two nuclei. By exploiting these measurements we determine the corresponding neutron skin values for ${}^{133}\mathrm{Cs}$ and ${}^{127}\mathrm{I}$. These results suggest a preference for models which predict large neutron skin values, as corroborated by the only other electroweak measurements of the neutron skin of ${}^{208}\mathrm{Pb}$ performed by PREX experiments. Moreover, for the first time, we obtain a data-driven APV+COHERENT measurement of the low-energy weak mixing angle with a percent uncertainty, independent of the value of the average neutron rms radius of ${}^{133}\mathrm{Cs}$ and ${}^{127}\mathrm{I}$, that is allowed to vary freely in the fit. The value of the low-energy weak mixing angle that we found is slightly larger than the standard model prediction.

A set of microscopic, covariant density-functional, and nonrelativistic Skyrme-type equations of state is employed to study the structure of purely nucleonic neutron stars at finite temperature. After examining the agreement with presently available astrophysical observational constraints, we find that the magnitude of thermal effects depends on the nucleon effective mass as well as on the stiffness of the cold equation of state. We evidence a fairly small but model-dependent effect of finite temperature on stellar stability that is correlated with the relative thermal pressure inside the star.

Recent experimental results for the cascade hypernucleus ${}_{\mathrm{\Xi }}{}^{15}\mathrm{C}$ (${}^{14}\mathrm{N}+{\mathrm{\Xi }}^{-}$) are analyzed together with data for ${}_{\mathrm{\Xi }}{}^{12}\mathrm{Be}$ and ${}_{\mathrm{\Xi }}{}^{13}\mathrm{B}$ within a Skyrme-Hartree-Fock theoretical approach. Optimal Skyrme parameters are determined for a consistent description of the KISO, IBUKI, KINKA, BNL-E885, BNL-E906, KEK-E224, and KEK-E176 data regarding these nuclei. The important role of deformation for ${}_{\mathrm{\Xi }}{}^{13}\mathrm{B}$ is pointed out. The shape of the ${\mathrm{\Xi }}^{-}$ mean field in ${}_{\mathrm{\Xi }}{}^{12}\mathrm{Be}$ is analyzed in some detail.

Although they are among the lightest nuclei, the hydrogen isotopes are not well understood both experimentally and theoretically. Indeed, besides the deuteron and triton, all known hydrogen isotopes are resonances of complex structure. Even more elusive is ${}^7\mathrm{H}$, which may have been observed experimentally and has been claimed to be a narrow resonance. Nevertheless, even its existence is controversial, and its theoretical study is difficult due to both its unbound character and large number of interacting valence nucleons. It is then the object of this paper to theoretically study the hydrogen isotopes ${}^{4–7}\mathrm{H}$ with the Gamow shell model and to perform, to our knowledge, the first direct calculation of unbound resonance hydrogen isotopes up to ${}^7\mathrm{H}$. As the Gamow shell model includes both continuum coupling and internucleon correlations, useful information can be obtained about poorly known unbound hydrogen isotopes. Our present calculations indicate that ${}^{4,6}\mathrm{H}$ ground states are fairly broad resonances, whereas those of ${}^{5,7}\mathrm{H}$ are narrow, which is in accordance with current experimental data. The results then suggest that, in particular, ${}^{5,7}\mathrm{H}$ should be more heavily studied, as they might well be among the most narrow neutron resonances of the light nuclear chart.

Global hyperon polarization, ${\overline{P}}_{\mathrm{H}}$, in $\mathrm{Au}+\mathrm{Au}$ collisions over a large range of collision energy, $\sqrt{s_{\mathrm{NN}}}$, was recently measured and successfully reproduced by hydrodynamic and transport models with intense fluid vorticity of the quark-gluon plasma. While naïve extrapolation of data trends suggests a large ${\overline{P}}_{\mathrm{H}}$ as the collision energy is reduced, the behavior of ${\overline{P}}_{\mathrm{H}}$ at small $\sqrt{s_{\mathrm{NN}}}<7.7$ GeV is unknown. Operating the STAR experiment in fixed-target mode, we measured the polarization of $\mathrm{\Lambda }$ hyperons along the direction of global angular momentum in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=3$ GeV. The observation of substantial polarization of $4.91\pm 0.81(\mathrm{stat}.)\pm 0.15(\mathrm{syst}.)\%$ in these collisions may require a reexamination of the viscosity of any fluid created in the collision, of the thermalization timescale of rotational modes, and of hadronic mechanisms to produce global polarization.

The search for the chiral magnetic effect (CME) has been a subject of great interest in the field of high-energy heavy-ion collision physics, and various observables have been proposed to probe the CME. Experimental observables are often contaminated with background contributions arising from collective motions (specifically elliptic flow) of the collision system. We present a method study of event-shape engineering (ESE) that projects the CME-sensitive ${\gamma }_{112}$ correlator and its variations (${\gamma }_{132}$ and ${\gamma }_{123}$) to a class of events with minimal flow. We discuss the realization of the zero-flow mode, the sensitivity on the CME signal, and the corresponding statistical significance for $\mathrm{Au}+\mathrm{Au}$, $\mathrm{Ru}+\mathrm{Ru}$, and $\mathrm{Zr}+\mathrm{Zr}$ collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV with a multiphase transport model, as well as a new event generator, event-by-event anomalous-viscous fluid dynamics.

The elliptic and triangular flow parameters of direct photons are known to be dominated by thermal radiations. The nonthermal contributions dilute the photon anisotropic flow by adding extra weight factor in the $v_n$ calculation. The discrepancy between experimental photon anisotropic flow data and results from theoretical model calculations is not well understood even after significant developments in the model calculations as well as in the experimental analysis methods. We show that the ratio of photon $v_n$ can be a potential observable in this regard by minimizing the nonthermal contributions. We calculate the $v_2/v_3$ of photons as a function of $p_T$ from heavy ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and compare the results with available experimental data. The ratio is found to be larger for peripheral collisions than for central collisions. However, the $p_T$ dependent behavior of the ratio is found to be different than the individual flow parameters. The ratio is found to be sensitive to the initial conditions of the model calculation at different $p_T$ regions compared to the individual anisotropic flow parameters. We show that the photon $v_1/v_2$ and $v_1/v_3$ along with the $v_2/v_3$ results may help us constrain the initial conditions in heavy ion collisions.

Two opposite parity bands I and II with eight new parity changing transitions have been identified in ${}^{79}\mathrm{Se}$ using the fusion-evaporation reaction ${}^{76}\mathrm{Ge}({}^9\mathrm{Be}$, $\alpha 2n$) at $E_{\mathrm{Lab}}\approx 31$ MeV. The $B\left(M1\right)$ and $B\left(E2\right)$ rates of bands I and II as well as $B\left(E1\right)$ values of the linking transitions between the two bands have been determined from lifetime measurements and are compared with reflection asymmetric triaxial particle rotor model calculations. The large $B\left(E1\right)$/$B\left(E2\right)$ ratios and $B\left(E1\right)$ transition rates indicate the existence of a strong octupole correlation in the ${}^{79}\mathrm{Se}$ nucleus. This is also supported by the calculated potential energy surface, based on the covariant density functional theory within the three-dimensional lattice approach, which is very soft for the octupole shape degree of freedom ${\beta }_{30}$. Extracted values of the intrinsic dipole moments $|D_0|$ from the $B\left(E1\right)$ rates for the lower spin states also indicate the octupole correlation in ${}^{79}\mathrm{Se}$.

The Coulomb and proximity potential model for deformed nuclei (CPPMDN) have been used to compute half-lives of two-proton ($2p$) radioactivity of ${}^6\mathrm{Be}, {}^{12}\mathrm{O}, {}^{16}\mathrm{Ne}, {}^{19}\mathrm{Mg}, {}^{45}\mathrm{Fe}, {}^{48}\mathrm{Ni}, {}^{54}\mathrm{Zn}$, and ${}^{67}\mathrm{Kr}$, and the values are compared with the experimental data. The predicted half-life values are also compared with six theoretical models and two empirical formulas. The standard deviation is least for the model CPPMDN ($\sigma =1.03$), compared to other theoretical models and formulas, which indicates that CPPMDN is the apt model for studying $2p$ radioactivity. I extended the model to predict half-lives of other 15 even-$Z$ nuclei for which $2p$ radioactivity is energetically possible with released energy, $Q_{2p}>0$, and hope that the predictions may serve as a guide for future experimental investigations. The observed linear nature of the new Geiger-Nuttall plot of ${log}_{10}\left[T_{1/2}\left(s\right)\right]$ computed using CPPMDN versus $(Z_d^{0.8}+{\ell }^{0.25})Q_{2p}^{-1/2}$, stresses the reliability of the model in predicting $2p$ radioactivity half-lives.

The impact of anisotropic pressure models in neutron stars (NSs) is increasing their compactness. Therefore, for the relatively soft NS equation of state (EOS), we can still obtain a relatively large maximum mass of NSs and a relatively short canonical NS radius. We systematically study the anisotropic NS properties using a refined EOS. We compare the results with the recent NS multimessenger constraints. We use a relativistic mean-field (RMF) model with the G3 parameter set to calculate the NS core EOSs. The standard SU(3) prescription and hyperon potential depths determine the hyperon coupling constants. We use the inner and outer crusts EOSs from Miyatsu et al. [Astrophys. J. 777, 4 (2013)]. We consider two kinds of EOSs at high densities: one with the maximum speed of sound in NS matter obeying the conformal bound, i.e., $v_s^{\max }=\frac{1}{\sqrt{3}}$ (WHSS) and one without considering this bound (WH). We have found for the WH EOS with $\mathrm{\Delta }=-1.8$ that NS properties predicted for an anisotropic NS based on the Horvat et al. model [Classical Quantum Gravity 28, 025009 (2011)] are entirely compatible with recent NS multimessenger constraints. Whether a $2.6M_{\odot }$ massive compact object observed in the GW190814 event is an anisotropic NS or not, we found that the compact object is not likely an anisotropic NS.

Background: The $\gamma$ decay of ${}^{12}\mathrm{C}$ levels above the particle emission threshold plays a crucial role in the production of ${}^{12}\mathrm{C}$ in astrophysical environments. The Hoyle state is fundamental in the helium-burning phase of red giant stars, while the 9.64-MeV level can be involved in higher temperature explosive environments.

Purpose: The aim of this work was to explore the feasibility of measuring the $\gamma$-decay widths of the 9.64-MeV state. The experiments were performed at Laboratori Nazionali del Sud of INFN (INFN-LNS), in Catania, using $\alpha$ and proton beams impinging on a carbon target.

Methods: The method used consists in the detection of all charged products and $\gamma$ rays emitted in the reaction, in order to strongly reduce the background.

Results: Few events of $\gamma$ decay of the 9.64-MeV level were observed in the reaction $\alpha +{}^{12}\mathrm{C}$. Also the decay yield of the Hoyle state was measured in both the measured reactions $\alpha +{}^{12}\mathrm{C}$ and $p+{}^{12}\mathrm{C}$.

Conclusions: The $\gamma$ decay of the 9.64-MeV level is, inside error bars, in reasonable agreement with the yield recently reported in literature by measuring the ${}^{12}\mathrm{C}$ residue. The observed yield is larger than previously accepted lower limit. Also, the decay yield of the Hoyle state seems larger than the one reported in literature, even if the limited statistics do not allow a definite conclusion.