We show how thermal mean field effects can be incorporated consistently in the hydrodynamical modeling of heavy-ion collisions. The nonequilibrium correction to the distribution function resulting from a temperature-dependent mass is obtained in a procedure which automatically satisfies the Landau matching condition and is thermodynamically consistent. The physics of the bulk viscosity is studied here for Boltzmann and Bose-Einstein gases within the Chapman-Enskog and 14-moment approaches in the relaxation time approximation. Constant and temperature-dependent masses are considered in turn. It is shown that, in the small mass limit, both methods lead to the same value of the ratio of the bulk viscosity to its relaxation time. The inclusion of a temperature-dependent mass leads to the emergence of the ${\beta }_{\lambda }$ function in that ratio, and it is of the expected parametric form for the Boltzmann gas, while for the Bose-Einstein case it is affected by the infrared cutoff. This suggests that the relaxation time approximation may be too crude to obtain a reliable form of $\zeta /{\tau }_R$ for gases obeying Bose-Einstein statistics.

A single, unifying measurement of the ${}^{239}\mathrm{Pu}$ capture cross section from 1 keV to 1.3 MeV has been performed for the first time using the Detector for Advanced Neutron Capture Experiments (DANCE) at the Los Alamos Neutron Science Center (LANSCE). The experimental method combines a prior experiment's characterization of prompt fission $\gamma$ rays in conjunction with a fission tagging detector with a separate experiment using a thick ${}^{239}\mathrm{Pu}$ sample to extract the neutron capture cross section in ratio to ${}^{239}\mathrm{Pu}(n,f)$. We have made new predictions of the capture cross section taking into account recent results for the $M1$ scissors mode present in other actinides. The results show deviations from current evaluations which are 30% higher at the highest energies, and will be used to improve calculations relevant for several applications.

As proposed recently by Fornal and Grinstein, neutrons can undergo a dark matter decay mode which has not yet been observed. Such a decay could explain the existing discrepancy between two different methods of neutron lifetime measurements. If such neutron decay is possible, then it should occur also in nuclei with sufficiently low neutron binding energy. We examine a few nuclear candidates for the dark neutron decay and we consider the possibilities of their experimental identification. In more detail we discuss the case of ${}^{11}\mathrm{Be}$ which appears as the most promising nucleus for the observation of neutron dark decay.

Background: Recent measurements of fusion cross sections for the ${}^{28}\mathrm{Si}+{}^{28}\mathrm{Si}$ system revealed a rather unsystematic behavior; i.e., they drop faster near the barrier than at lower energies. This was tentatively attributed to the large oblate deformation of ${}^{28}\mathrm{Si}$ because coupled-channels (CC) calculations largely underestimate the ${}^{28}\mathrm{Si}+{}^{28}\mathrm{Si}$ cross sections at low energies, unless a weak imaginary potential is applied, probably simulating the deformation. ${}^{30}\mathrm{Si}$ has no permanent deformation and its low-energy excitations are of a vibrational nature. Previous measurements of this system reached only 4 mb, which is not sufficient to obtain information on effects that should show up at lower energies.

Purpose: The aim of the present experiment was twofold: (i) to clarify the underlying fusion dynamics by measuring the symmetric case ${}^{30}\mathrm{Si}+{}^{30}\mathrm{Si}$ in an energy range from around the Coulomb barrier to deep sub-barrier energies, and (ii) to compare the results with the behavior of ${}^{28}\mathrm{Si}+{}^{28}\mathrm{Si}$ involving two deformed nuclei.

Methods: ${}^{30}\mathrm{Si}$ beams from the XTU tandem accelerator of the Laboratori Nazionali di Legnaro of the Istituto Nazionale di Fisica Nucleare were used, bombarding thin metallic ${}^{30}\mathrm{Si}$ targets (50 $\mu \mathrm{g}$/${\mathrm{cm}}^2$) enriched to $99.64\%$ in mass 30. An electrostatic beam deflector allowed the detection of fusion evaporation residues (ERs) at very forward angles, and angular distributions of ERs were measured.

Results: The excitation function of ${}^{30}\mathrm{Si}+{}^{30}\mathrm{Si}$ was measured down to the level of a few microbarns. It has a regular shape, at variance with the unusual trend of ${}^{28}\mathrm{Si}+{}^{28}\mathrm{Si}$. The extracted logarithmic derivative does not reach the $L_{\mathrm{CS}}$ limit at low energies, so that no maximum of the $S$ factor shows up. CC calculations were performed including the low-lying $2^{+}$ and $3^{-}$ excitations.

Conclusions: Using a Woods-Saxon potential the experimental cross sections at low energies are overpredicted, and this is a clear sign of hindrance, while the calculations performed with a M3Y + repulsion potential nicely fit the data at low energies, without the need of an imaginary potential. The comparison with the results for ${}^{28}\mathrm{Si}+{}^{28}\mathrm{Si}$ strengthens the explanation of the oblate shape of ${}^{28}\mathrm{Si}$ being the reason for the irregular behavior of that system.

The shell effects in multinucleon transfer process are investigated in the systems ${}^{136}\mathrm{Xe}$ + ${}^{198}\mathrm{Pt}$ and ${}^{136}\mathrm{Xe}$ + ${}^{208}\mathrm{Pb}$ within the dinuclear system (DNS) model. The temperature dependence of shell corrections on potential energy surface is taken into account in the DNS model and remarkable improvement for description of experimental data is noticed. The reactions ${}^{136}\mathrm{Xe}$ + ${}^{186}\mathrm{W}$ and ${}^{150}\mathrm{Nd}$ + ${}^{186}\mathrm{W}$ are also studied. It is found that due to shell effects the projectile ${}^{150}\mathrm{Nd}$ is more promising for producing transtarget nuclei rather than ${}^{136}\mathrm{Xe}$ with neutron shell closure.

Charge-dependent azimuthal correlations of same- and opposite-sign pairs with respect to the second- and third-order event planes have been measured in $p\text{Pb}$ collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=8.16\text{TeV}$ and $\text{PbPb}$ collisions at 5.02 TeV with the CMS experiment at the LHC. The measurement is motivated by the search for the charge separation phenomenon predicted by the chiral magnetic effect (CME) in heavy ion collisions. Three- and two-particle azimuthal correlators are extracted as functions of the pseudorapidity difference, the transverse momentum ($p_{\mathrm{T}}$) difference, and the $p_{\mathrm{T}}$ average of same- and opposite-charge pairs in various event multiplicity ranges. The data suggest that the charge-dependent three-particle correlators with respect to the second- and third-order event planes share a common origin, predominantly arising from charge-dependent two-particle azimuthal correlations coupled with an anisotropic flow. The CME is expected to lead to a $v_2$-independent three-particle correlation when the magnetic field is fixed. Using an event shape engineering technique, upper limits on the $v_2$-independent fraction of the three-particle correlator are estimated to be 13% for $p\text{Pb}$ and 7% for $\text{PbPb}$ collisions at 95% confidence level. The results of this analysis, both the dominance of two-particle correlations as a source of the three-particle results and the similarities seen between $\text{PbPb}$ and $p\text{Pb}$, provide stringent constraints on the origin of charge-dependent three-particle azimuthal correlations and challenge their interpretation as arising from a chiral magnetic effect in heavy ion collisions.

We carry out the study of finite nuclei, infinite nuclear matter, and neutron star properties with the newly developed relativistic force, the Institute of Physics Bhubaneswar-I (IOPB-I). Using this force, we calculate the binding energies, charge radii, and neutron-skin thickness for some selected nuclei. From the ground-state properties of superheavy nuclei ($Z=120$), it is noticed that considerable shell gaps appear at neutron numbers $N=172$, 184, and 198, manifesting the magicity at these numbers. The low-density behavior of the equation of state for pure neutron matter is compatible with other microscopic models. Along with the nuclear symmetry energy, its slope and curvature parameters at the saturation density are consistent with those extracted from various experimental data. We calculate the neutron star properties with the equation of state composed of nucleons and leptons in $\beta$-equilibrium, which are in good agreement with the x-ray observations by Steiner [Astrophys. J. 722, 33 (2010)] and Nättilä [Astron. Astrophys. 591, A25 (2016)]. Based on the recent observation of GW170817 with a quasi-universal relation, Rezzolla et al. [Astrophys. J. Lett. 852, L25 (2018)] have set a limit for the maximum mass that can be supported against gravity by a nonrotating neutron star in the range $2.01\pm 0.04\lesssim M\left(M_{\odot }\right)\lesssim 2.16\pm 0.03$. We find that the maximum mass of the neutron star for the IOPB-I parametrization is $2.15M_{\odot }$. The radius and tidal deformability of a canonical neutron star of mass $1.4M_{\odot }$ are 13.2 km and $3.9\times {10}^{36}\mathrm{g}{\mathrm{cm}}^2{\mathrm{s}}^2$, respectively.

We study the energy dependence of global polarization of ${\displaystyle \mathrm{\Lambda }}$ hyperons in peripheral Au-Au collisions. We combine the calculation of vorticity and strange chemical potential in the framework of the kinetic quark-gluon-string model with the anomalous mechanism related to the axial vortical effect. We pay special attention to the temperature-dependent contribution related to the holographic gravitational anomaly and find that the preliminary data from the BNL Relativistic Heavy Ion Collider are compatible with its suppression discovered earlier in lattice calculations.

Different versions of the effective-range function method for charged particle collisions are studied and compared. In addition, a novel derivation of the standard effective-range function is presented from the analysis of Coulomb wave functions in the complex plane of the energy. The recently proposed effective-range function denoted as ${\displaystyle {\mathrm{\Delta }}_{\ell }}$ [Ramírez Suárez and Sparenberg, Phys. Rev. C 96, 034601 (2017)] and an earlier variant [Hamilton et al., Nucl. Phys. B 60, 443 (1973)] are related to the standard function. The potential interest of ${\displaystyle {\mathrm{\Delta }}_{\ell }}$ for the study of low-energy cross sections and weakly bound states is discussed in the framework of the proton-proton ${}^1\mathrm{S}_0$ collision. The resonant state of the proton-proton collision is successfully computed from the extrapolation of ${\displaystyle {\mathrm{\Delta }}_{\ell }}$ instead of the standard function. It is shown that interpolating ${\displaystyle {\mathrm{\Delta }}_{\ell }}$ can lead to useful extrapolation to negative energies, provided scattering data are known below one nuclear Rydberg energy (${\displaystyle 12.5\mathrm{keV}}$ for the proton-proton system). This property is due to the connection between ${\displaystyle {\mathrm{\Delta }}_{\ell }}$ and the effective-range function by Hamilton et al. that is discussed in detail. Nevertheless, such extrapolations to negative energies should be used with caution because ${\displaystyle {\mathrm{\Delta }}_{\ell }}$ is not analytic at zero energy. The expected analytic properties of the main functions are verified in the complex energy plane by graphical color-based representations.

Background: Proton-induced $\alpha$-knockout reactions may allow direct experimental observation of $\alpha$ clustering in nuclei. This is obtained by relating the theoretical descriptions of clustering states to the experimental reaction observables. It is desired to introduce microscopic structure models into the theoretical frameworks for $\alpha$-knockout reactions.

Purpose: Our goal is to probe the $\alpha$ clustering in the ${}^{10}\mathrm{Be}$ nucleus by proton-induced $\alpha$-knockout reaction observables.

Method: We adopt an extended version of the Tohsaki-Horiuchi-Schuck-Röpke wave function of ${}^{10}\mathrm{Be}$ and integrate it with the distorted-wave impulse approximation framework for the calculation of $(p,p\alpha )$-knockout reactions.

Results: We make the first calculation for the ${}^{10}\mathrm{Be}(p,p\alpha ){}^6\mathrm{He}$ reaction at 250 MeV by implementing a microscopic $\alpha$-cluster wave function, and we predict the triple-differential cross section (TDX). Furthermore, by constructing artificial states of the target nucleus ${}^{10}\mathrm{Be}$ with compact or dilute spatial distributions, the TDX is found to be highly sensitive to the extent of clustering in the target nuclei.

Conclusions: These results provide reliable manifestation of $\alpha$ clustering in ${}^{10}\mathrm{Be}$.

Prior studies of nonequilibrium dynamics using anisotropic hydrodynamics have used the relativistic Anderson-Witting scattering kernel or some variant thereof. In this paper, we make the first study of the impact of using a more realistic scattering kernel. For this purpose, we consider a conformal system undergoing transversally homogenous and boost-invariant Bjorken expansion and take the collisional kernel to be given by the leading order $2\leftrightarrow 2$ scattering kernel in scalar $\lambda {\varphi }^4$. We consider both classical and quantum statistics to assess the impact of Bose enhancement on the dynamics. We also determine the anisotropic nonequilibrium attractor of a system subject to this collisional kernel. We find that, when the near-equilibrium relaxation-times in the Anderson-Witting and scalar collisional kernels are matched, the scalar kernel results in a higher degree of momentum-space anisotropy during the system's evolution, given the same initial conditions. Additionally, we find that taking into account Bose enhancement further increases the dynamically generated momentum-space anisotropy.

We theoretically investigate a possibility of an ${\eta }^{\prime }d$ bound state and its formation in the $\gamma d\to \eta d$ reaction. First, in the fixed center approximation to the Faddeev equations, we obtain an ${\eta }^{\prime }d$ bound state with a binding energy of $25\text{MeV}$ and width of $19\text{MeV}$, where we take the ${\eta }^{\prime }N$ interaction with a coupling to the $\eta N$ channel from the linear $\sigma$ model. Then, in order to investigate the feasibility from an experimental point of view, we calculate the cross section of the $\gamma d\to \eta d$ reaction at the photon energy in the laboratory frame around $1.2\text{GeV}$. As a result, we find a clear peak structure with the strength $\sim 0.2\text{nb}/\text{sr}$, corresponding to a signal of the ${\eta }^{\prime }d$ bound state in case of backward $\eta$ emission. This structure will be prominent because a background contribution coming from single-step $\eta$ emission off a bound nucleon is highly suppressed. In addition, the signal can be seen even in case of forward $\eta$ emission as a bump or dip, depending on the relative phase between the bound-state formation and the single-step background.

Proton inelastic scattering of ${}^{72,74}\mathrm{Ni}$ and ${}^{76,80}\mathrm{Zn}$ ions at energies around 235 MeV/nucleon was performed at the Radioactive Isotope Beam Factory and studied using $\gamma$-ray spectroscopy. Angular integrated cross sections for direct inelastic scattering to the $2_1^{+}$ and $4_1^{+}$ states were measured. The Jeukenne-Lejeune-Mahaux folding model, extended beyond 200 MeV, was used together with neutron and proton densities stemming from quasiparticle random-phase approximation (QRPA) calculations to interpret the experimental cross sections and to infer neutron to proton matrix element ratios. In addition, coupled-channels calculations with a phenomenological potential were used to determine deformation lengths. For the Ni isotopes, correlations favor neutron excitations, thus conserving the $Z=28$ gap. A dominance of proton excitation, on the other hand, is observed in the Zn isotopes, pointing to the conservation of the $N=50$ gap approaching ${}^{78}\mathrm{Ni}$. These results are in agreement with QRPA and large-scale shell-model calculations.

With the Wigner function moments (WFM) method the scissors mode of the actinides and rare earth nuclei are investigated. The unexplained experimental fact that in ${}^{232}\mathrm{Th}$ a double hump structure is found finds a natural explanation within WFM. It is predicted that the lower peak corresponds to an isovector spin scissors mode whereas the higher-lying states corresponds to the conventional isovector orbital scissors mode. The experimental situation is scrutinized in this respect concerning practically all results of $M1$ excitations.

Significant excesses of $J/\psi$ yield at very low transverse momentum ($p_T<0.3$ GeV/$c$) were observed by the ALICE and STAR collaborations in peripheral hadronic $A+A$ collisions. This is a sign of coherent photoproduction of $J/\psi$ in violent hadronic interactions. Theoretically, the photoproduction of $J/\psi$ in hadronic collisions raises questions about how spectator and nonspectator nucleons participate in the coherent reaction. We argue that the strong interactions in the overlapping region of incoming nuclei may disturb the coherent production, leaving room for different coupling assumptions. The destructive interference between photoproduction on ions moving in opposite directions also needs to be included. This paper presents calculations of $J/\psi$ production from coherent photon-nucleus ($\gamma +A\to J/\psi +A$) interactions in hadronic $A+A$ collisions at BNL Relativistic Heavy Ion Collider and CERN Large Hadron Collider energies with both nucleus and spectator coupling hypotheses. The integrated yield of coherent $J/\psi$ as a function of centrality is found to be significantly different, especially towards central collisions, for different coupling scenarios. Differential distributions as a function of transverse momentum, azimuthal angle, and rapidity in different centrality bins are also shown, and found to be more sensitive to the Pomeron coupling than to the photon coupling. These predictions call for future experimental measurements to help better understand the coherent interaction in hadronic heavy-ion collisions.

Cross sections for elastic and inelastic scattering of the weakly bound ${}^9\mathrm{Be}$ nucleus on a ${}^{120}\mathrm{Sn}$ target have been measured at seven bombarding energies around and above the Coulomb barrier. The elastic angular distributions are analyzed with a four-body continuum-discretized coupled-channels (CDCC) calculation, which considers ${}^9\mathrm{Be}$ as a three-body projectile ($\alpha +\alpha +n$). An optical model analysis using the São Paulo potential is also shown for comparison. The CDCC analysis shows that the coupling to the continuum part of the spectrum is important for the agreement with experimental data even at energies around the Coulomb barrier, suggesting that breakup is an important process at low energies. At the highest incident energies, two inelastic peaks are observed at 1.19(5) and 2.41(5) MeV. Coupled-channels (CC) calculations using a rotational model confirm that the first inelastic peak corresponds to the excitation of the $2_1^{+}$ state in ${}^{120}\mathrm{Sn}$, while the second one likely corresponds to the excitation of the $3_1^{-}$ state.

Using the α-cluster structure of colliding nuclei, the elastic scattering of ${}^6\mathrm{Li}+{}^{28}\mathrm{Si}$ at energies from 76 to 318 MeV has been investigated by the use of the real folding cluster approach. The results of the cluster analysis are compared with those obtained by the CDM3Y6 effective density- and energy-dependent nucleon-nucleon (NN) interaction based upon $G$-matrix elements of the M3Y-Paris potential. A Woods-Saxon (WS) form was used for the imaginary potential. For all energies and derived potentials, the diffraction region was well reproduced, except at $E_{\mathrm{lab}}=135$ and 154 MeV at large angle. These results suggest that the addition of the surface (DWS) imaginary potential term to the volume imaginary potential is essential for a correct description of the refractive structure of the ${}^6\mathrm{Li}$ elastic scattering distribution at these energies. The energy dependence of the total reaction cross sections and that of the real and imaginary volume integrals is also discussed.

Background: Recent time-dependent Hartree-Fock-Bogoliubov (TDHFB) calculations predict that superfluidity enhances fluctuations of the fusion barrier. This effect is not fully understood and not yet experimentally revealed.

Purpose: The goal of this study is to empirically investigate the effect of superfluidity on the distribution width of the fusion barrier.

Method: Two new methods are proposed in the present study. First, the local regression method is introduced and used to determine the barrier distribution. The second method, which requires only the calculation of an integral of the cross section, is developed to determine accurately the fluctuations of the barrier. This integral method, showing the best performance, is systematically applied to 115 fusion reactions.

Results: Fluctuations of the barrier for open-shell systems are, on average, larger than those for magic or semimagic nuclei. This is due to the deformation and the superfluidity. To disentangle these two effects, a comparison is made between the experimental width and the width estimated from a model that takes into account the tunneling, the deformation, and the vibration effect. This study reveals that superfluidity enhances the fusion barrier width.

Conclusions: This analysis shows that the predicted effect of superfluidity on the width of the barrier is real and is of the order of 1 MeV.