We show that the cusplike structure in the nuclear symmetry energy, a consequence of topology change, visible in the skyrmion lattice description of dense matter, is extremely robust. It is present in the Skyrme model—with the pion field only—and is left unscathed by massive degrees of freedom such as the vector mesons $\rho$ and $\omega$ and also the scalar meson introduced as a dilaton. It leads to the emergence of parity-doubling at the skyrmion–half-skyrmion transition and impacts on the nuclear symmetry energy “wilderness” landscape, weeding out roughly half of the wilderness. It is shown that a pseudoconformal sound velocity arises at a precocious density at which the cusp is formed. It is suggested that the topology change, being robust, could impact on the tidal deformability observed in gravity waves

Fine structure in the $\alpha$ decay of high-spin states in ${}^{156}\mathrm{Lu}$ and ${}^{158}\mathrm{Ta}$ has been identified by means of $\alpha \gamma$-coincidence analysis. One new $\alpha$ decay from ${}^{156}\mathrm{Lu}$ and two from ${}^{158}\mathrm{Ta}$ were identified, one of which was found to populate a previously unknown state in ${}^{154}\mathrm{Lu}$. The hindrance-factor systematics from all four odd-odd, $N=85$ nuclei with known $\alpha$-decaying, $\pi h_{11/2}$ coupled states were reviewed and are discussed. These proved consistent with the previously assigned $\left(\pi h_{11/2}\nu h_{9/2}\right){10}^{+}$ configuration of the $\alpha$-decaying state in ${}^{156}\mathrm{Lu}$, which differs from the $\left(\pi h_{11/2}\nu f_{7/2}\right)9^{+}$ assignments in the other three nuclei.

The decay of an excited ${}^{24}\mathrm{Mg}$ nucleus into six $\alpha$ particles is studied, from a selection of central ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ reactions at 95 MeV beam energy, measured with the GARFIELD-RCo apparatus. Kinematic correlations among the detected $\alpha$ particles allow investigating the decay mechanism leading to the full disassembly of ${}^{24}\mathrm{Mg}$ into $\alpha$ particles. Experimental data indicate that the decay proceeds through intermediate doorway states involving excited states of ${}^{12}\mathrm{C}$ and ${}^8\mathrm{Be}$, with an important branching ratio estimated to be of the order of 40%. The possibility of a simultaneous breakup of the hot source in three bodies ($\alpha$, ${}^8\mathrm{Be}$, ${}^{12}\mathrm{C}$) is excluded in favor of a sequential emission. This is confirmed by comparison with statistical model predictions, where the emission of ${}^8\mathrm{Be}$ in both its ground state and first excited state is considered. Residual differences with respect to the statistical model are observed, particularly in the branching ratio of the Hoyle state with respect to higher excitation energy ${}^{12}\mathrm{C}$ states.

The parity-violating (PV) nucleon-nucleon $\left(NN\right)$ interaction in the three-nucleon system is investigated using pionless effective field theory $\left(\mathrm{EFT}(\pi /)\right)$. This work shows that a next-to-leading order (NLO) PV three-body force is necessary, in contradiction with a previous claim [H. W. Grießhammer and M. R. Schindler, Eur. Phys. J. A 46, 73 (2010)]. Including three-body $P$- to $D$-wave transitions, PV three-nucleon observables are calculated to higher energies than previously considered. Using the recent large-$N_C$ analysis of the PV $NN$ interaction in $\mathrm{EFT}(\pi /)$, the current understanding of low energy PV few-body measurements is reassessed. The recent measurement of the asymmetry $A_{\gamma }$ in $\vec{n}p\to d\gamma$ from the NPDGamma Collaboration [D. Blyth et al. (NPDGamma), Phys. Rev. Lett. 121, 242002 (2018)], gives the value $g_4^{\left(N_C^{-1}\right)}=[-1.4\pm 0.63\left(\text{stat.}\right)\pm 0.09\left(\text{syst.}\right)]\times {10}^{-10}{\mathrm{MeV}}^{-1}$ for a next-to-next-to-leading order $\left({\mathrm{N}}^2\mathrm{LO}\right)$ in large-$N_C$ low energy constant (LEC). Using the large-$N_C$ hierarchy of LECs, the sizes of the leading order (LO) in large-$N_C$ LECs are estimated using an experimental bound on a parity violating asymmetry in $\vec{p}d$ scattering at $E_{\mathrm{lab}}=15$ MeV and a measurement of $\vec{p}p$ scattering at $E_{\mathrm{lab}}=13.6$ MeV. Comparing the size of the resulting $\mathrm{LO}(\mathcal{O}\left(N_C\right))$ in large-$N_C$ LECs to the ${\mathrm{N}}^2\mathrm{LO}(\mathcal{O}\left(N_C^{-1}\right))$ in large-$N_C$ LEC $g_4^{\left(N_C^{-1}\right)}$ shows they are roughly the same size, in contradiction with current large-$N_C$ counting.

The success of the ambitious programs of both long- and short-baseline neutrino-oscillation experiments employing liquid-argon time-projection chambers will greatly rely on the precision with which the weak response of the argon nucleus can be estimated. In the E12-14-012 experiment at Jefferson Lab Hall A, we studied the properties of the argon nucleus by scattering a high-quality electron beam off a high-pressure gaseous argon target. Here, we present the measured ${}^{40}\mathrm{Ar}(e,e^{\prime })$ double differential cross section at incident electron energy $E=2.222$ GeV and scattering angle $\theta =15.{54}^{\circ }$. The data cover a broad range of energy transfers, where quasielastic scattering and delta production are the dominant reaction mechanisms. The result for argon is compared to our previously reported cross sections for titanium and carbon, obtained in the same kinematical setup.

The level densities of ${}^{74,76}\mathrm{Ge}$ nuclei are studied with ${}^{68,70}\mathrm{Zn}({}^7\mathrm{Li},\mathrm{Xp})$ reactions. Proton evaporation spectra are measured at backward angles in a wide energy region, from about 2 to 25 MeV. The analysis of spectra allows for the testing of level density models used in modern reaction codes for practical cross-section calculations. Our results show that at excitation energies above the discrete level region, all level density models tested in this work overestimate the level densities that are needed to reproduce proton spectra from these reactions. The Gilbert and Cameron model, which includes the constant-temperature energy dependence of the level density, shows the best agreement with experiment, however, its parameters need to be adjusted to reflect the observed reduction of the level density at higher excitation energies.

General expressions for all parity-conserving polarization observables of elastic electron-nucleon scattering in the one-photon exchange approximation are derived for a general frame of reference, i.e., not assuming scattering off a nucleon at rest and not specializing to a specific system of coordinates. Essentially, the given expressions are also valid for the inverse process, i.e., nucleon scattering off electrons.

The proton-neutron symplectic model with Sp(12,$R$) dynamical algebra is applied to the description of the microscopic structure of the low-lying negative-parity states of the $K^{\pi }=0_1^{-}$ and $K^{\pi }=1_1^{-}$ bands in ${}^{154}\mathrm{Sm}$ without the introduction of additional degrees of freedom that are inherent to other approaches to odd-parity nuclear states. For this purpose, the model Hamiltonian is diagonalized in a U(6)-coupled basis, restricted to state space spanned by the fully symmetric U(6) irreps of the lowest odd irreducible representation of Sp(12,$R$). In this way, the positive- and negative-parity collective bands are treated on equal footing within the framework of the microscopic symplectic-based shell-model scheme. A good description of the energy levels of the two bands under consideration, as well as the reproduction of some energy splitting quantities which are usually introduced in the literature as a measure of the octupole correlations, is obtained. The microscopic structure of low-lying collective states with negative-parity in ${}^{154}\mathrm{Sm}$ shows that practically there are no admixtures from the higher shells and hence the presence of a very good U(6) dynamical symmetry. Additionally, the structure of the collective states under consideration shows also the presence of a good SU(3) quasidynamical symmetry.

The heaviest currently known nuclei, which have up to 118 protons, have been produced in ${}^{48}\mathrm{Ca}$ induced reactions with actinide targets. Among them, the element tennessine (Ts), which has 117 protons, has been synthesized by fusing ${}^{48}\mathrm{Ca}$ with the radioactive target ${}^{249}\mathrm{Bk}$, which has a half-life of 327 d. The experiment was performed at the gas-filled recoil separator TASCA. Two long and two short $\alpha$ decay chains were observed. The long chains were attributed to the decay of ${}^{294}\mathrm{Ts}$. The possible origin of the short-decay chains is discussed in comparison with the known experimental data. They are found to fit with the decay chain patterns attributed to ${}^{293}\mathrm{Ts}$. The present experimental results confirm the previous findings at the Dubna Gas-Filled Recoil Separator on the decay chains originating from the nuclei assigned to Ts.

We formulate the Jost function formalism based on the Hartree-Fock-Bogoliubov (HFB) theory which has been used to represent the nature of nuclear superfluidity. By using the Jost function based on the HFB, the $S$-matrix for the neutron elastic scattering by the open-shell nucleus can be represented analytically. Adopting the Woods-Saxon potential, we calculate the $S$-matrix poles and their trajectories by varying the pairing strength using the Jost function in order to see the pairing effect on the complex energy-momentum plane. The total cross sections of neutron elastic scattering are also analyzed, and some sharp or asymmetrical resonances (from the configuration mixing) due to the pairing effect are found in the cross section.

We present measurements of azimuthal correlations of charged hadron pairs in $\sqrt{s_{\mathit{NN}}}=200$ GeV $\mathrm{Au}+\mathrm{Au}$ collisions for the trigger and associated particle transverse-momentum ranges of $1<p_T^t<10\mathrm{GeV}/c$ and $0.5<p_T^a<10\mathrm{GeV}/c$. After subtraction of an underlying event using a model that includes higher-order azimuthal anisotropy $v_2, v_3$, and $v_4$, the away-side yield of the highest trigger-$p_T$($p_T^t>4\mathrm{GeV}/c$) correlations is suppressed compared with that of correlations measured in $p+p$ collisions. At the lowest associated particle $p_T$($0.5<p_T^a<1\mathrm{GeV}/c$), the away-side shape and yield are modified relative to those in $p+p$ collisions. These observations are consistent with the scenario of radiative-jet energy loss. For the low-$p_T$ trigger correlations ($2<p_T^t<4\mathrm{GeV}/c$), a finite away-side yield exists and we explore the dependence of the shape of the away-side within the context of an underlying-event model. Correlations are also studied differentially versus event-plane angle ${\mathrm{\Psi }}_2$ and ${\mathrm{\Psi }}_3$. The angular correlations show an asymmetry when selecting the sign of the difference between the trigger-particle azimuthal angle and the ${\mathrm{\Psi }}_2$ event plane. This asymmetry and the measured suppression of the pair yield out-of-plane is consistent with a path-length-dependent energy loss. No ${\mathrm{\Psi }}_3$ dependence can be resolved within experimental uncertainties.

We extend our earlier study on two-particle angular correlations in $pp$ collisions at low transverse momentum ($p_T$) to $p$-Pb, Pb-Pb, and Au-Au collisions at BNL Relativistic Heavy Ion Collider and CERN Large Hadron Collider energies. We mainly use the string melting version of a multiphase transport model with improved quark coalescence for this study. We start from the analysis of ${\pi }^{\pm },K^{\pm }$, and $p$($\overline{p}$) $p_T$ and rapidity distributions at different centralities. We then focus on two-particle angular correlations in $p$-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV and Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV. For $p$-Pb collisions, a near side depression in the angular correlation is observed for low $p_T$ proton pairs and $\mathrm{\Lambda }$ pairs but not for pion pairs or kaon pairs, similar to our earlier finding for $pp$ collisions at $\sqrt{s}=7$ TeV. This is also the case for very low multiplicity Pb-Pb and Au-Au collisions. We also find that parton interactions and the improved quark coalescence are mainly responsible for the depression feature in baryon pair angular correlations. However, no such baryon-baryon anticorrelations are observed in Pb-Pb and Au-Au collisions at higher multiplicities. Therefore our results suggest that low $p_T$ baryon-baryon angular anticorrelations have a strong multiplicity dependence.

Background: The ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ reaction is a widely studied nuclear reaction; however, it is still not understood with the required precision. It has a great importance both in Big Bang nucleosynthesis and in solar hydrogen burning. The low mass number of the reaction partners makes it also suitable for testing microscopic calculations.

Purpose: Despite the high number of experimental studies, none of them addresses the ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ reaction cross sections above 3.1-MeV center-of-mass energy. Recently, a previously unobserved resonance in the ${}^6\mathrm{Li}(\mathrm{p},\gamma ){}^7\mathrm{Be}$ reaction suggested a new level in ${}^7\mathrm{Be}$, which would also have an impact on the ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ reaction in the energy range above 4.0 MeV. The aim of the present experiment is to measure the ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ reaction cross section in the energy range of the proposed level.

Method: For this investigation the activation technique was used. A thin window gas-cell target confining ${}^3\mathrm{He}$ gas was irradiated using an $\alpha$ beam. The ${}^7\mathrm{Be}$ produced was implanted into the exit foil. The ${}^7\mathrm{Be}$ activity was determined by counting the $\gamma$ rays following its decay by a well-shielded high-purity germanium detector.

Results: Reaction cross sections have been determined between $E_{\text{cm}}=4.0\text{and}4.4$ MeV with 0.04-MeV steps covering the energy range of the proposed nuclear level. One lower-energy cross-section point was also determined to be able to compare the results with previous studies.

Conclusions: A constant cross section of around 10.5 $\mu \mathrm{b}$ was observed around the ${}^7\mathrm{Be}$ proton separation energy. An upper limit of 45 neV for the strength of a ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ resonance is derived.

Magnetic fields of order ${10}^{15}$ G have been measured at the surface of some neutron stars, and much stronger magnetic fields are expected to be present in the solid region beneath the surface. The effects of the magnetic field on the equation of state and on the composition of the crust due to Landau-Rabi quantization of electron motion are studied. Both the outer and inner crustal regions are described in a unified and consistent way within the nuclear-energy density functional theory.

The $T_z=-\frac{3}{2}$ nucleus ${}^{21}\mathrm{Mg}$ has been studied by Coulomb excitation on ${}^{196}\mathrm{Pt}$ and ${}^{110}\mathrm{Pd}$ targets. A 205.6(1)-keV $\gamma$-ray transition resulting from the Coulomb excitation of the ${\frac{5}{2}}^{+}$ ground state to the first excited ${\frac{1}{2}}^{+}$ state in ${}^{21}\mathrm{Mg}$ was observed for the first time. Coulomb excitation cross-section measurements with both targets and a measurement of the half-life of the ${\frac{1}{2}}^{+}$ state yield an adopted value of $B(E2;{\frac{5}{2}}^{+}\to {\frac{1}{2}}^{+})=13.3\left(4\right)$ W.u. A new excited state at 1672(1) keV with tentative ${\frac{9}{2}}^{+}$ assignment was also identified in ${}^{21}\mathrm{Mg}$. This work demonstrates a large difference in the $B(E2;{\frac{5}{2}}^{+}\to {\frac{1}{2}}^{+})$ value between $T=\frac{3}{2}, A=21$ mirror nuclei. The difference is investigated in the shell-model framework employing both isospin conserving and breaking USD interactions and using modern ab initio nuclear structure calculations, which have recently become applicable in the $sd$ shell.

Background: The recent observation of the unbound nucleus ${}^{11}\mathrm{O}$ offers the unique possibility to study how the structure and dynamics of two-proton ($2p$) decay is affected by the removal of one neutron from ${}^{12}\mathrm{O}$, and provides important information on the Thomas-Ehrman effect in the mirror pairs ${}_8{}^{11}\mathrm{O}_3\text{−}{}_3{}^{11}\mathrm{Li}_8$ and ${}_8{}^{12}\mathrm{O}_4\text{−}{}_4{}^{12}\mathrm{Be}_8$, which involve the $2p$ emitters ${}^{11}\mathrm{O}$ and ${}^{12}\mathrm{O}$.

Purpose: We investigate how continuum effects impact the structure and decay properties of ${}^{11}\mathrm{O}$ and ${}^{12}\mathrm{O}$, and their mirror partners.

Methods: We solve the three-body core-nucleon-nucleon problem using the Gamow coupled-channel (GCC) method. The GCC Hamiltonian employs a realistic finite-range valence nucleon-nucleon interaction and the deformed cores of ${}^{9,10}\mathrm{C}$, ${}^9\mathrm{Li}$, and ${}^{10}\mathrm{Be}$.

Results: We calculate the energy spectra and decay widths of ${}^{11}\mathrm{O}$ and ${}^{12}\mathrm{O}$ as well as those of their mirror nuclei. In particular, we investigate the dynamics of the $2p$ decay in the ground state of ${}^{12}\mathrm{O}$ by analyzing the evolution of the $2p$ configuration of the emitted protons as well as their angular correlations in the coordinate space. We also show how the analytic structure of the resonant states of ${}^{10}\mathrm{Li}$ and ${}^{10}\mathrm{N}$ impacts the low-lying states of ${}^{11}\mathrm{Li}$ and ${}^{11}\mathrm{O}$.

Conclusions: We demonstrate that, in both nuclei ${}^{11}\mathrm{O}$ and ${}^{12}\mathrm{O}$, there is a competition between direct and “democratic” $2p$ ground-state emission. The broad structure observed in ${}^{11}\mathrm{O}$ is consistent with four broad resonances, with the predicted $3/2_1^{-}$ ground state strongly influenced by the broad threshold resonant state in ${}^{10}\mathrm{N}$, which is an isobaric analog of the antibound (or virtual) state in ${}^{10}\mathrm{Li}$.

A triaxial projected shell model including configurations with more than four quasiparticles in the configuration space is developed and applied to investigate the recently reported five chiral doublets candidates in a single even-even nucleus ${}^{136}\mathrm{Nd}$. The energy spectra and transition probability ratios $B\left(M1\right)/B\left(E2\right)$ are reproduced satisfactorily. The configuration mixing along the rotational bands is studied by analyzing the intrinsic composition of the eigenfunctions. The chiral geometry of these nearly degenerate bands is examined by the K plot and the azimuthal plot, and the evolution from the chiral vibration to the static chirality with spin is clearly demonstrated for four pairs of partner bands. For bands D3 and D3-C, due to strong configuration mixing, their azimuthal plots show features of planar rotation and it is difficult to interpret them as chiral partners.

A central extension of the proton-neutron symplectic model (PNSM) with the semidirect structure $\mathrm{wsp}(12,R)\equiv \left[\mathrm{hw}\right(6\left)\right]\mathrm{sp}(12,R)$ is proposed. This extension, among its generators, contains the electric dipole operator, which allows one to calculate the reduced $E1$ transition strengths. The required matrix elements of the dipole transition operator are given explicitly. Using these matrix elements, I calculate the low-energy $B\left(E1\right)$ transition strengths between the states of the ground band and $K^{\pi }=0_1^{-}$ band for ${}^{154}\mathrm{Sm}$ and ${}^{238}\mathrm{U}$ and compare them with experiment. The results obtained reproduce well the experimental data for the two nuclei under consideration without the use of an effective charge, which could be considered as a significant achievement of the present approach.

The production cross sections of neutron-rich fission residues in reactions induced by ${}^{238}\mathrm{U}$ projectiles at $950A$ MeV impinging on Pb and Be targets are investigated at the Fragment Separator at GSI. These two targets allow us to investigate fission processes induced by two reaction mechanisms, Coulomb and nuclear excitations, and to study the role of these mechanisms in the neutron excess of the final fragments.

We investigate the impact of hydrodynamic fluctuations on correlation functions in a scale invariant fluid with a conserved $\text{U}\left(1\right)$ charge. The kinetic equations for the two-point functions of pressure, momentum, and heat energy densities are derived within the framework of stochastic hydrodynamics. The leading nonanalytic contributions to the energy-momentum tensor as well as the $\text{U}\left(1\right)$ current are determined from the solutions to these kinetic equations. In the case of a static homogeneous background we show that the long time tails obtained from hydrokinetic equations reproduce the one-loop results derived from statistical field theory. We use these results to establish bounds on transport coefficients. We generalize the stochastic equation to a background flow undergoing Bjorken expansion. We compute the leading fractional power $\mathcal{O}({\left(\tau T\right)}^{-3/2})$ correction to the $\text{U}\left(1\right)$ current and compare with the first-order gradient term.