The charge (mass) distributions of fission fragments resulting from low- and high-energy fission of the even-even nuclei ${}^{254-260,264}\mathrm{Fm}$, ${}^{258-264}\mathrm{No}$, and ${}^{262-266}\mathrm{Rf}$ are studied with the statistical scission-point model. The calculated results are compared with the available experimental data. In contrast to the experimental data, the calculated mass distribution for ${}^{258}\mathrm{Fm}$(s.f.) is strikingly similar to the experimental one for ${}^{257}\mathrm{Fm}$(s.f.). The transformation of the shape of charge distribution with increasing isospin and excitation energy occurs gradually and in a similar fashion like that of the mass distribution, but slower. For ${}^{254}$Fm(i.f.), ${}^{257}$Fm($n_{th}$,f), and ${}^{260}\mathrm{Fm}$(s.f.), the unexpected difference (symmetric or asymmetric) between the shapes of charge and mass distributions is predicted for the first time. At some critical excitation energy, the saturation of the symmetric component of charge (mass) yields is demonstrated.

A formalism to study the mode-by-mode response to the energy deposition of external hard partons propagating in a relativistic fluid is developed, based on a semianalytical solution of conformal fluid dynamics. The soft-particle production resulting from the jet-medium interaction is calculated, and the recoil of the viscous medium is studied for different orientations of the relativistic jets and for different values of the specific shear viscosity $\eta /s$.

In this article, we calculate the magnetization and other thermodynamical quantities for strongly magnetized quark matter within the Nambu–Jona-Lasinio model at zero temperature. We assume two scenarios: chemically equilibrated charge neutral matter present in the interiors of compact stars and zero-strangeness isospin-symmetric matter created in nuclear experiments. We show that the magnetization oscillates with density but in a much more smooth form than what was previously shown in the literature. As a consequence, we do not see the unphysical behavior in the pressure in the direction perpendicular to the magnetic field that was previously found. Finally, we also analyze the effects of a vector interaction on our results.

The collective structures of ${}^{75}\mathrm{Ge}$ have been studied for the first time via the ${}^{74}\mathrm{Ge}(\alpha ,2p1n){}^{75}\mathrm{Ge}$ fusion-evaporation reaction. Two negative-parity bands and one tentative positive-parity band built on the $\nu p_{1/2},\nu f_{5/2}$, and $\nu g_{9/2}$ states, respectively, are established and compared with the structures in the neighboring $N=43$ isotones. According to the configuration-constrained potential-energy surface calculations, a shape transition from oblate to prolate along the isotopic chain in odd-$A$ Ge isotopes is suggested to occur at ${}^{75}\mathrm{Ge}$. The properties of the bands in ${}^{75}\mathrm{Ge}$ are analyzed in comparison with the triaxial particle rotor model calculations.

The proton-proton momentum correlation function from different rapidity regions is systematically investigated for the Au + Au collisions at different impact parameters and different energies from $400A$ MeV to $1500A$ MeV in the framework of the isospin-dependent quantum molecular dynamics model complemented by the Lednický-Lyuboshitz analytical method. In particular, the in-medium nucleon-nucleon cross-section dependence of the correlation function is brought into focus, while the impact parameter and energy dependence of the momentum correlation function are also explored. The sizes of the emission source are extracted by fitting the momentum correlation functions using the Gaussian source method. We find that the in-medium nucleon-nucleon cross section obviously influences the proton-proton momentum correlation function, which is from the whole-rapidity or projectile or target rapidity region at smaller impact parameters, but there is no effect on the mid-rapidity proton-proton momentum correlation function, which indicates that the emission mechanism differs between projectile or target rapidity and mid-rapidity protons.

The normalized ${}^{238}\mathrm{U}(n,f)/{}^{235}\mathrm{U}(n,f)$ cross section ratio has been measured using the NIFFTE fission Time Projection Chamber (fissionTPC) from the reaction threshold to $30\mathrm{MeV}$. The fissionTPC is a two-volume MICROMEGAS time projection chamber that allows for full three-dimensional reconstruction of fission-fragment ionization profiles from neutron-induced fission. The measurement was performed at the Los Alamos Neutron Science Center, where the neutron energy is determined from neutron time of-flight. The ${}^{238}\mathrm{U}(n,f)/{}^{235}\mathrm{U}(n,f)$ ratio reported here is the first cross section measurement made with the fissionTPC, and will provide new experimental data for evaluation of the ${}^{238}\mathrm{U}(n,f)$ cross section, an important standard used in neutron-flux measurements. Use of a development target in this work prevented the determination of an absolute normalization, to be addressed in future measurements. Instead, the measured cross section ratio has been normalized to ENDF/B-VIII.$\beta 5$ at 14.5 MeV.

We evaluate the effects of preequilibrium dynamics on observables in ultrarelativistic heavy-ion collisions. We simulate the initial nonequilibrium phase within a multiphase transport (AMPT) model, while the subsequent near-equilibrium evolution is modeled using (2+1)-dimensional relativistic viscous hydrodynamics. We match the two stages of evolution carefully by calculating the full energy-momentum tensor from AMPT and using it as input for the hydrodynamic evolution. We find that when the preequilibrium evolution is taken into account, final-state observables are insensitive to the switching time from AMPT to hydrodynamics. Unlike some earlier treatments of preequilibrium dynamics, we do not find the initial shear viscous tensor to be large. With a shear viscosity to entropy density ratio of 0.12, our model describes quantitatively a large set of experimental data on Pb+Pb collisions at the Large Hadron Collider over a wide range of centrality: differential anisotropic flow $v_n\left(p_T\right)(n=2–6)$, event-plane correlations, correlation between $v_2$ and $v_3$, and cumulant ratio $v_2\left\{4\right\}/v_2\left\{2\right\}$.

The low-energy recoiling ions from the $\beta$ decay of ${}^{134}\mathrm{Sb}$ were studied by using the Beta-decay Paul Trap. Using this apparatus, singly charged ions were suspended in vacuum at the center of a detector array used to detect emitted $\beta$ particles, $\gamma$ rays, and recoil ions in coincidence. The recoil ions emerge from the trap with negligible scattering, allowing $\beta$-decay properties and the charge-state distribution of the daughter ions to be determined from the $\beta$-ion coincidences. First-forbidden $\beta$-decay theory predicts a $\beta \text{−}\nu$ correlation coefficient of nearly unity for the $0^{-}$ to $0^{+}$ transition from the ground state of ${}^{134}\mathrm{Sb}$ to the ground state of ${}^{134}\mathrm{Te}$. Although this transition was expected to have a nearly 100% branching ratio, an additional 17.2(52)% of the $\beta$-decay strength must populate high-lying excited states to obtain an angular correlation consistent with unity. The extracted charge-state distribution of the recoiling ions was compared with existing $\beta$-decay results and the average charge state was found to be consistent with the results from lighter nuclei.

In this work we reinvestigate the spectroscopy of ${}^{13}\mathrm{C}$ at excitation energies larger than the $\alpha$ emission threshold ($E_x>10.648\mathrm{MeV}$) by means of a comprehensive $R$-matrix fit of experimental data concerning $\alpha +{}^9\mathrm{Be}$ collisions at low energies. Owing to the analysis of many reaction channels in a broad energy range, we improved the current knowledge on the level scheme of ${}^{13}\mathrm{C}$, by contributing to remove uncertain $J^{\pi }$ assignments for several states. Some tentative speculations on the existence of molecular bands associated to cluster structures in this nucleus are also discussed.

Spontaneous breaking of continuous symmetries of a nuclear many-body system results in the appearance of zero-energy restoration modes. These so-called spurious Nambu-Goldstone modes represent a special case of collective motion and are sources of important information about the Thouless-Valatin inertia. The main purpose of this work is to study the Thouless-Valatin rotational moment of inertia as extracted from the Nambu-Goldstone restoration mode that results from the zero-frequency response to the total-angular-momentum operator. We examine the role and effects of the pairing correlations on the rotational characteristics of heavy deformed nuclei in order to extend our understanding of superfluidity in general. We use the finite-amplitude method of the quasiparticle random-phase approximation on top of the Skyrme energy density functional framework with the Hartree-Fock-Bogoliubov theory. We have successfully extended this formalism and established a practical method for extracting the Thouless-Valatin rotational moment of inertia from the strength function calculated in the symmetry-restoration regime. Our results reveal the relation between the pairing correlations and the moment of inertia of axially deformed nuclei of rare-earth and actinide regions of the nuclear chart. We have also demonstrated the feasibility of the method for obtaining the moment of inertia for collective Hamiltonian models. We conclude that from the numerical and theoretical perspective, the finite-amplitude method can be widely used to effectively study rotational properties of deformed nuclei within modern density functional approaches.

The cross section of the ${}^{197}\mathrm{Au}(n,2n){}^{196}\mathrm{Au}$ reaction has been determined at six energies ranging from 15.3–20.9 MeV by means of the activation technique, relative to the ${}^{27}\mathrm{Al}(n,\alpha ){}^{24}\mathrm{Na}$ reaction. Quasimonoenergetic neutron beams were produced via the ${}^3\mathrm{H}(d,n){}^4\mathrm{He}$ reaction at the 5.5 MV Tandem T11/25 accelerator laboratory of NCSR “Demokritos”. After the irradiations, the induced $\gamma$-ray activity of the target and reference foils was measured with high-resolution HPGe detectors. The cross section for the high spin isomeric state (${12}^{-}$) was determined along with the sum of the ground ($2^{-}$), the first ($5^{+}$), and second (${12}^{-}$) isomeric states. Theoretical calculations were carried out with the codes empire 3.2.2 and talys 1.8. Optimum input parameters were chosen in such a way as to simultaneously reproduce several experimental reaction channel cross sections in a satisfactory way, namely the ($n,\mathrm{elastic}$), ($n,2n$), ($n,3n$), ($n,p$), ($n,\alpha$), and ($n$,total) ones.

The transfer yields mass spectra were measured in ${}^{11}\mathrm{B},{}^{12,13}\mathrm{C},{}^{28}\mathrm{Si}\left({}^{18}\mathrm{O},{}^{17}\mathrm{O}\right)$ and ${}^{11}\mathrm{B},{}^{12,13}\mathrm{C},{}^{28}\mathrm{Si}\left({}^{18}\mathrm{O},{}^{16}\mathrm{O}\right)$ reactions at 84 MeV. The two-neutron transfer (2NT) and the one-neutron transfer (1NT) cross sections were extracted for all the systems. The 2NT cross section is found comparable to the 1NT one and remarkably larger than that predicted assuming no correlations among the two transferred nucleons and only natural parity states are populated via the $\left({}^{18}\mathrm{O},{}^{16}\mathrm{O}\right)$ two-neutron transfer reaction. Calculations based on the constrained molecular dynamics model show that such behavior is uniquely a consequence of neutron pairing correlations in the ${}^{18}\mathrm{O}$ ground state.

The potential-energy surfaces of an extended set of heavy and superheavy even-even nuclei with $92\le Z\le 126$ and isospins $40\le N-Z\le 74$ are evaluated within the recently developed Fourier shape parametrization. Ground-state and decay properties are studied for 324 different even-even isotopes in a four-dimensional deformation space, defined by nonaxiality, quadrupole, octupole, and hexadecapole degrees of freedom. Nuclear deformation energies are evaluated in the framework of the macroscopic-microscopic approach, with the Lublin-Strasbourg drop model and a Yukawa-folded mean-field potential. The evolution of the ground-state equilibrium shape (and possible isomeric, metastable states) is studied as a function of $Z$ and $N$. $\alpha$-decay $Q$ values and half-lives, as well as fission-barrier heights, are deduced. In order to understand the transition from asymmetric to symmetric fission along the Fm isotopic chain, the properties of all identified fission paths are investigated. Good agreement is found with experimental data wherever available. New interesting features about the population of different fission modes for nuclei beyond Fm are predicted.

We discuss the forward-backward correlations of harmonic flow in $\mathrm{Pb}+\mathrm{Pb}$ collisions at the CERN Large Hadron Collider, applying standard multibin measures as well as new measures proposed here. We illustrate the methods with hydrodynamic model simulations based on event-by-event initial conditions from the wounded quark model with asymmetric rapidity emission profiles. Within the model, we examine independently the event-plane angle and the flow magnitude decorrelations. We find a specific hierarchy between various flow decorrelation measures and confirm certain factorization relations. We find qualitative agreement of the model and the data from the ATLAS and CMS Collaborations.

A protoneutron star (PNS) is a newly formed compact object in a core collapse supernova. In this paper, the neutrino emission from the cooling process of a PNS is investigated using two types of nuclear equation of state (EOS). It is found that the neutrino signal is mainly determined by the high-density EOS. The neutrino luminosity and mean energy are higher and the cooling time scale is longer for the softer EOS. Meanwhile, the neutrino mean energy and the cooling time scale are also affected by the low-density EOS because of the difference in the population of heavy nuclei. Heavy nuclei have a large scattering cross section with neutrinos owing to the coherent effects and act as thermal insulation near the surface of a PNS. The neutrino mean energy is higher and the cooling time scale is longer for an EOS with a large symmetry energy at low densities, namely a small density derivative coefficient of the symmetry energy, $L$.

The shell-model-like approach is implemented to treat the cranking many-body Hamiltonian based on the covariant density functional theory including pairing correlations with exact particle number conservation. The self-consistency is achieved by iterating the single-particle occupation probabilities back to the densities and currents. As an example, the rotational structures observed in the neutron-rich nucleus ${}^{60}\mathrm{Fe}$ are investigated and analyzed. Without introducing any ad hoc parameters, the bandheads, the rotational spectra, and the relations between the angular momentum and rotational frequency for the positive-parity band A and negative-parity bands B and C are well reproduced. The essential role of the pairing correlations is revealed. It is found that for band A, the band crossing is due to the change of the last two occupied neutrons from the $1f_{5/2}$ signature partners to the $1g_{9/2}$ signature partners. For the two negative-parity signature partner bands B and C, the band crossings are due to the pseudocrossing between the $1f_{7/2,5/2}$ and the $1f_{5/2,1/2}$ orbitals. Generally speaking, the deformation parameters $\beta$ for bands A, B, and C decrease with rotational frequency. For band A, the deformation jumps from $\beta \approx 0.19$ to $\beta \approx 0.29$ around the band crossing. In comparison with its signature partner band C, band B exhibits appreciable triaxial deformation.

The charge-symmetry-breaking (CSB) effect in a nuclear medium that gives rise to the first-order symmetry energy in finite nuclei is discussed in detail in the present paper. For heavy and superheavy nuclei with large neutron excesses, it should be nonnegligible in high-precision mass predictions, and importantly it affects the stability of these nuclei. Combined with this CSB effect, the Coulomb energy is constrained by using the experimental Coulomb displacement energy of mirror nuclei, and then the mass-dependent symmetry energy coefficients of heavy nuclei are reextracted with the experimental ${\beta }^{-}$-decay energies of heavy odd-$A$ nuclei and with the experimental mass differences. Based on these results, we probe the neutron skin thickness $\mathrm{\Delta }{R}_{np}$ of ${}^{208}\mathrm{Pb}$ and the density-dependent symmetry energy coefficient of nuclear matter. $\mathrm{\Delta }{R}_{np}$ in ${}^{208}\mathrm{Pb}$ is found to be $0.158\pm 0.014\mathrm{fm}$, and the slopes $L$ of the symmetry energy coefficient at densities of $\rho =0.16$ and $\rho =0.11{\mathrm{fm}}^{-3}$ are estimated to be $42\pm 8$ and $42\pm 3\mathrm{MeV}$, respectively. These results would be meaningful to discriminate between the models and the predictions that are relevant for the investigations on properties of nuclei and of neutron stars.

The Borromean drip-line nucleus ${}^{17}\mathrm{Ne}$ has been suggested to possess a two-proton halo structure in its ground state. In the astrophysical $rp$-process, where the two-proton capture reaction ${}^{15}\mathrm{O}(2p,\gamma ){}^{17}\mathrm{Ne}$ plays an important role, the calculated reaction rate differs by several orders of magnitude between different theoretical approaches. To add to the understanding of the ${}^{17}\mathrm{Ne}$ structure we have studied nuclear and electromagnetic dissociation. A 500 MeV/u ${}^{17}\mathrm{Ne}$ beam was directed toward lead, carbon, and polyethylene targets. Oxygen isotopes in the final state were measured in coincidence with one or two protons. Different reaction branches in the dissociation of ${}^{17}\mathrm{Ne}$ were disentangled. The relative populations of $s$ and $d$ states in ${}^{16}\mathrm{F}$ were determined for light and heavy targets. The differential cross section for electromagnetic dissociation (EMD) shows a continuous internal energy spectrum in the three-body system ${}^{15}\mathrm{O}+2p$. The ${}^{17}\mathrm{Ne}$ EMD data were compared to current theoretical models. None of them, however, yields satisfactory agreement with the experimental data presented here. These new data may facilitate future development of adequate models for description of the fragmentation process.

Background: Since the first experimental observation, two-nucleon radioactivity has gained renewed attention since the early 2000s. The ${}^6\mathrm{Be}$ system is the lightest two-proton ground-state emitter, while ${}^{16}\mathrm{Be}$ was recently proposed to be the first two-neutron ground-state emitter ever observed. A proper understanding of their properties and decay modes requires a reasonable description of the three-body continuum.

Purpose: Study the ground-state properties of ${}^6\mathrm{Be}$ and ${}^{16}\mathrm{Be}$ within a general three-body model and investigate their nucleon-nucleon correlations in the continuum.

Method: The pseudostate (PS) method in hyperspherical coordinates, using the analytical transformed harmonic oscillator (THO) basis for three-body systems, is used to construct the ${}^6\mathrm{Be}$ and ${}^{16}\mathrm{Be}$ ground-state wave functions. These resonances are approximated as a stable PS around the known two-nucleon separation energy. Effective core-$N$ potentials, constrained by the available experimental information on the binary subsystems ${}^5\mathrm{Li}$ and ${}^{15}\mathrm{Be}$, are employed in the calculations.

Results: The ground state of ${}^{16}\mathrm{Be}$ is found to present a strong dineutron configuration, with the valence neutrons occupying mostly an $l=2$ state relative to the core. The results are consistent with previous $R$-matrix calculations for the actual continuum. The case of ${}^6\mathrm{Be}$ shows a clear symmetry with respect to its mirror partner, the two-neutron halo ${}^6\mathrm{He}$: The diproton configuration is dominant, and the valence protons occupy an $l=1$ orbit.

Conclusions: The PS method is found to be a suitable tool in describing the properties of unbound $\text{core}+N+N$ ground states. For both ${}^{16}\mathrm{Be}$ and ${}^6\mathrm{Be}$, the results are consistent with previous theoretical studies and confirm the dominant dinucleon configuration. This favors the picture of a correlated two-nucleon emission.