Prompt thermal neutron capture $\gamma$-ray cross sections ${\sigma }_{\gamma }$ were measured for the ${}^{23}$Na($n$,$\gamma$) reaction with guided cold neutron beams at the Budapest Reactor. The ${}^{24}$Na $\gamma$-ray cross sections were internally standardized with a stoichiometric NaCl target by using standard ${}^{35}$Cl($n$,$\gamma$)${}^{36}$Cl $\gamma$-ray cross sections. Transitions were assigned to levels in ${}^{24}$Na based primarily upon the known nuclear structure information from the literature, producing a nearly complete neutron capture decay scheme. The total radiative thermal neutron cross section ${\sigma }_0$ was determined from the sum of prompt $\gamma$-ray cross section populating the ground state as 0.540 (3) b, and from the activation $\gamma$-ray cross sections for the decay of ${}^{24}$Na as 0.542 (3) b. The isomer cross section ${\sigma }_0$ (${}^{23}$Na${}^m$, $t_{1/2}=20.20\text{ms})=0.501\left(3\right)$ b and the ${}^{24}$Na neutron separation energy $S_n=6959.352\left(18\right)$ keV were also determined in these experiments. New level spins and parities were proposed on the basis of new transition assignments and the systematics of reduced transition probabilities for the primary $\gamma$ rays.

Based on the hydrodynamic approach, the formation of exotic structures in head-on heavy ion collisions at 60 MeV/nucleon is explained. The physical explanation of the different structures' formation with dependence on the incompressibility coefficient is suggested. Within the developed approach the Rayleigh-Plateau mechanism is confirmed to be the origin of the fragments in the case of “stiff” equation of state of nuclear matter (with an incompressibility of 380 MeV). The cold breakdown of the system is suggested to be caused by the presence of the Coulomb force. The obtained results are compared with the existing Boltzmann-like theory calculations and the experimental data for the “doughnut” -like geometries.

The expanding dynamics in central ${}^{129}$ Xe + ${}^{120}$Sn collisions at 50 MeV/nucleon is investigated within the framework of the isospin-dependent quantum molecular dynamics model in combination with the statistical decay code gemini. The nonisotropic distributions in the fragment size and average kinetic energy are reproduced. The collective expansion energy and the Coulomb explosion energy of different fragments are extracted. We focus on the nonisotropic explosion of the colliding system and the difference of explosion energies of H, He, Li, and Be fragments. The radial flow energies are extracted at the polar angle ${\theta }_{c.m.}$ = 90${}^{\circ }$. From studying the beam energy dependence at 50–125 MeV/nucleon, the threshold energies of the radial flow are investigated. The time evolutions of the density and the collective velocity are investigated. It is found that the radial flow causes the system to expand in the isotropic direction, whereas the residual incident energy causes the system to extend along the longitudinal direction. The Pauli blocking is responsible for the nonisotropic nature of the collective velocity.

Recent relativistic mean field (RMF) calculations have provided nuclear distributions of some isotopes whose mass numbers are much larger than atomic numbers. For helium isotopes, the RMF calculation seems to be inappropriate because of the small mass numbers; however, applicable results are obtained for ${}^{6,8}$He nuclei. The author calculates observables of proton elastic scattering from the helium isotopes and discusses relations between observables and nuclear distributions of the isotopes by comparison of the calculated results with experimental data. The calculations are based on relativistic impulse approximation (RIA) at incident proton energy: 71 MeV for ${}^{4,6,8}$He, 300 and 500 MeV for ${}^4$He, and 0.7 GeV for ${}^6$He. Scattering observables are predicted for ${}^{6,8}$He at 200 MeV.

Starting from the Feynman diagram representation of multiple scattering we consider the polarized ${\chi }_c$(1$P$)-charmonia production in antiproton-nucleus reactions close to the threshold ($p_{\mathrm{lab}}=5–7$ GeV/$c$). The rescattering and absorption of the incoming antiproton and outgoing charmonium on nucleons are taken into account, including the possibility of the elastic and nondiagonal (flavor-conserving) scattering ${\chi }_{cJ}N\to {\chi }_{c{J}^{\prime }}N$, $J,J^{\prime }=0,1,2$. The elementary amplitudes of the latter processes are evaluated by expanding the physical ${\chi }_c$ states in the Clebsch-Gordan series of the $c\overline{c}$ states with fixed values of internal orbital angular momentum ($L_z$) and spin projections on the ${\chi }_c$ momentum axis. The total interaction cross sections of these $c\overline{c}$ states with nucleons have been calculated in previous works using the QCD factorization theorem and the nonrelativistic quarkonium model, and turned out to be strongly $L_z$ dependent due to the transverse size difference. This directly leads to finite values of the ${\chi }_c$-nucleon nondiagonal scattering amplitudes. We show that the ${\chi }_{c0}N\to {\chi }_{c2}N$ transitions significantly influence the ${\chi }_{c2}$ production with helicity zero at small transverse momenta. This can serve as a signal in future experimental tests of the quark structure of ${\chi }_c$ states by the PANDA Collaboration at the Facility for Antiproton and Ion Research (FAIR).

Neutral-current photon emission reactions with nucleons and nuclei are studied. These processes are important backgrounds for ${\nu }_{\mu }\to {\nu }_e$ $({\overline{\nu }}_{\mu }\to {\overline{\nu }}_e)$ appearance oscillation experiments where electromagnetic showers instigated by electrons (positrons) and photons are not distinguishable. At intermediate energies, these reactions are dominated by the weak excitation of the $\Delta \left(1232\right)$ resonance and its subsequent decay into $N\gamma$. There are also nonresonant contributions that, close to threshold, are fully determined by the effective chiral Lagrangian of strong interactions. In addition, we have also included mechanisms mediated by nucleon excitations ($N^{*}$) from the second resonance region above the $\Delta \left(1232\right)$. From these states, the contribution of the $D_{13}$ $N^{*}\left(1520\right)$ turns out to be sizable for (anti)neutrino energies above 1.5 GeV. We have extended the model to nuclear targets taking into account Pauli blocking, Fermi motion, and the in-medium $\Delta$ resonance broadening. We present our predictions for both the incoherent and coherent channels, showing the relevance of the nuclear corrections. We also discuss the target mass dependence of the cross sections. This study is important to reduce systematic effects in neutrino oscillation experiments.

We extract the mass-dependent symmetry energy coefficients $a_{\mathrm{sym}}\left(A\right)$ with the nuclear mass differences reducing the uncertainties as far as possible. The estimated $a_{\mathrm{sym}}\left(A\right)$ of ${}^{208}\mathrm{Pb}$ is $22.4\pm 0.3$ MeV, which is further used to analyze the density-dependent nuclear matter symmetry energy at subsaturation densities. The slope parameter of the symmetry energy at the saturation density ${\rho }_0$ is $L=50.0\pm 15.5$ MeV. Furthermore, it is found that at the density of $\rho =0.69{\rho }_0=0.11$ fm${}^{-3}$, the symmetry energy $S(\rho =0.11{\mathrm{fm}}^{-3})=25.98\pm 0.01$ MeV and the corresponding slope parameter is $L=49.6\pm 6.2$ MeV, which are consistent with other independent analyses.

We consider nucleon-nucleon ($NN$) interactions from chiral effective field theory applying the $N/D$ method. The dynamical input is given by the discontinuity of the $NN$ partial-wave amplitudes across the left-hand cut (LHC) calculated in chiral perturbation theory by including one-pion exchange (OPE), once-iterated OPE, and leading irreducible two-pion exchange. We discuss both uncoupled and coupled partial waves. We show algebraically that the resulting integral equation has a unique solution when the input is taken only from OPE because it is of the Fredholm type with a squared integrable kernel and an inhomogeneous term. Phase shifts and mixing angles are typically rather well reproduced, and a clear improvement of the results obtained previously with only OPE is manifest. We also show that the contributions to the discontinuity across the LHC are amenable to a chiral expansion. Our method also establishes correlations between the $S$-wave effective ranges and scattering lengths based on unitarity, analyticity, and chiral symmetry.

The fragmentation of relativistic uranium projectiles has been exploited at the Gesellschaft für Schwerionenforschung laboratory to investigate the $\beta$ decay of neutron-rich nuclei just beyond ${}^{208}$Pb. This paper reports on $\beta$-delayed $\gamma$ decays of ${}^{211–213}$Tl, ${}^{215}$Pb, and ${}^{215–219}$Bi de-exciting states in the daughters ${}^{211–213}$Pb, ${}^{215}$Bi, and ${}^{215–219}$Po. The resulting partial level schemes, proposed with the help of systematics and shell-model calculations, are presented. The role of allowed Gamow-Teller and first-forbidden $\beta$ transitions in this mass region is discussed.

We use halo effective field theory to analyze the universal features of proton halo nuclei bound due to a large $S$-wave scattering length. Our work provides a fully field-theoretical treatment of bound halo nuclei in the presence of a repulsive Coulomb interaction. With a Lagrangian built from effective core and valence-proton fields, we derive a leading-order expression for the charge form factor. Within the same framework we also calculate the radiative proton capture cross section. We present general results at leading order that can be applied to any one-proton halo system bound in a relative $S$ wave. We illustrate the method by studying the excited $1/2^{+}$ state of fluorine 17, for which we give results for the charge radius and the astrophysical $S$ factor.

Consideration of its energy, angular-distribution shape, and magnitude of a cross section in the reaction He($p,t$) leads me to conclude that the 5.3-MeV state is likely 0${}^{+}$.

The excited states in ${}^{107}$Ag were populated through the heavy-ion fusion evaporation reaction ${}^{100}$Mo (${}^{11}$B, 4$n$) ${}^{107}$Ag at a beam energy of 46 MeV. Lifetimes of high-spin states in ${}^{107}$Ag have been measured through the Doppler shift attenuation method. The deduced $B\left(M1\right)$ values, gradually decreasing with increasing spin, clearly demonstrate that both the yrast positive-parity band and the yrast negative-parity band in ${}^{107}$Ag are magnetic rotation bands. Furthermore, experimental deduced $B\left(M1\right)$ values for the yrast positive-parity band are compared with the predictions of the particle rotor model. The approximate agreement between theoretical calculations and experimental results further confirms the mechanism of magnetic rotation for the yrast positive-parity band. In addition, a systematic investigation shows the evolution of the magnetic rotation mechanism in the $A\approx 110$ mass region.

A four-dimensional dynamical model was developed and applied to study fission characteristics in a wide range of a fissility parameter. Three collective shape coordinates and the $K$ coordinate were considered dynamically from the ground-state deformation to the scission into fission fragments. A modified one-body mechanism for nuclear dissipation with a reduction coefficient $k_s$ of the contribution from a “wall” formula has been used in the study. The inclusion of the $K$ coordinate in the dynamical consideration and use of the “chaos-weighted wall formula” with a deformation-dependent scaling factor $k_s\left(q_1\right)$ lead to fairly good reproduction of the variances of the fission-fragment mass distribution and the prescission neutron multiplicity for a number of fissioning compound nuclei in a wide fissility range. The four-dimensional dynamical calculations describe better experimental prescission neutron multiplicity and variances of fission-fragment mass distribution for heaviest nuclei with respect to a three-dimensional dynamical model, where the $K$ coordinate is assumed to be equal to zero. The estimate of a dissipation coefficient for the orientation degree of freedom, ${\gamma }_K\simeq 0.077$ ${\left(\text{MeV}\text{zs}\right)}^{-1/2}$, is good for heavy nuclei and a larger value of ${\gamma }_K\simeq 0.2$ ${\left(\text{MeV}\text{zs}\right)}^{-1/2}$ is needed for nuclei with mass $A_{\mathrm{CN}}$ $\simeq$ 200.

In this paper, we explore whether or not quark deconfinement may occur in high-mass neutron stars such as J1614 − 2230 ($1.97\pm 0.04M_{\odot }$) and J0348 + 0432 ($2.01\pm 0.04M_{\odot }$). Our study is based on a nonlocal extension of the SU(3) Nambu–Jona-Lasinio (n3NJL) model with repulsive vector interactions among the quarks. This model goes beyond the frequently used local version of the Nambu–Jona-Lasinio (NJL) model by accounting for several key features of QCD which are not part of the local model. Confined hadronic matter is treated in the framework of nonlinear relativistic mean field theory. We find that both the local as well as the nonlocal NJL model predict the existence of extended regions of mixed quark-hadron (quark-hybrid) matter in high-mass neutron stars with masses of 2.1 to $2.4M_{\odot }$. Pure quark matter in the cores of neutron stars is obtained for certain parametrizations of the hadronic lagrangian and choices of the vector repulsion among quarks. The radii of high-mass neutron stars with quark-hybrid matter and/or pure quark matter cores in their centers are found to lie in the canonical range of 12 to 13 km.

The low-energy structure of ${}^{46}$Ar is of particular interest due to the possible coexistence of different shapes and the possible existence of proton “bubble” structures. In this work, we apply a beyond relativistic mean-field approach to study the low-energy structure of ${}^{46}$Ar. Correlations beyond the mean field are introduced by configuration mixing of both particle-number and angular-momentum projected axially deformed mean-field states. The low-lying spectroscopy and charge density in a laboratory frame are calculated and an excellent agreement with available data is achieved. Even though an evident proton bubble structure is shown in the spherical state of ${}^{46}$Ar, it eventually disappears after taking into account the dynamical correlation effects. Moreover, our results indicate that the existence of a proton bubble structure in argon isotopes is unlikely.

Background: Many different shape degrees of freedom play crucial roles in determining the nuclear ground state and saddle point properties and the fission path. For the study of nuclear potential energy surfaces, it is desirable to have microscopic and self-consistent models in which all known important shape degrees of freedom are included.

Purpose: By breaking both the axial and the spatial reflection symmetries simultaneously, we develop multidimensionally-constrained relativistic mean field (MDC-RMF) models.

Methods: The nuclear shape is assumed to be invariant under the reversion of $x$ and $y$ axes, i.e., the intrinsic symmetry group is $V_4$ and all shape degrees of freedom ${\beta }_{\lambda \mu }$ with even $\mu$, such as ${\beta }_{20}$, ${\beta }_{22}$, ${\beta }_{30}$, ${\beta }_{32}$, ${\beta }_{40}$, $...,$ are included self-consistently. The single-particle wave functions are expanded in an axially deformed harmonic oscillator (ADHO) basis. The RMF functional can be one of the following four forms: the meson exchange or point-coupling nucleon interactions combined with the nonlinear or density-dependent couplings. The pairing effects are taken into account with the BCS approach.

Results: The one-, two, and three-dimensional potential energy surfaces of ${}^{240}$Pu are illustrated for numerical checks and for the study of the effect of the triaxiality on the fission barriers. Potential energy curves of even-even actinide nuclei around the first and second fission barriers are studied systematically. Besides the first ones, the second fission barriers in these nuclei are also lowered considerably by the triaxial deformation. This lowering effect is independent of the effective interactions used in the RMF functionals. Further discussions are made about different predictions on the effect of the triaxiality between the macroscopic-microscopic and MDC-RMF models, possible discontinuities on PES's from self-consistent approaches, and the restoration of broken symmetries.

Conclusions: MDC-RMF models give a reasonably good description of fission barriers of even-even actinide nuclei. It is important to include both the nonaxial and the reflection asymmetric shapes simultaneously for the study of potential energy surfaces and fission barriers of actinide nuclei and of those in unknown mass regions such as, e.g., superheavy nuclei.

The breakup of the projectile-like fragments in reactions induced by ${}^6$Li beams on a ${}^{144}$Sm target at energies close to the Coulomb barrier has been measured through the coincident detection of the emitted light particles. The emphasis of the measurements and the data analysis were placed in the complete characterization of the $\alpha$-deuteron breakup mode by means of the identification of the breakup fragments and the determination of the total $Q$ value, relative energy of the breakup products, and the angular distribution of their emission. Within the ranges of these variables covered by the present measurements, the results for the ${}^6$Li$\to$$d$+$\alpha$ mode show a clear dominance of the resonant channel through the 3${}^{+}$ state at 2.186 MeV over other resonant and nonresonant channels. Differential cross sections as a function of the center-of-mass angles of the intermediate binary collision and of the breakup emission, as well as integrated cross sections as a function of energy, have been obtained. The data are compared with those measured for competing processes in the same system and with the results of calculations based on a dynamic classical model that describes noncapture breakup, incomplete fusion, and complete fusion.

Background: A significant quenching of high energy jets was observed in the heavy ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC) facility, and is now confirmed at the CERN Large Hadron Collider (LHC) facility. The RHIC plus LHC era provides a unique opportunity to study the jet-medium interaction that leads to the jet quenching, and the medium itself at different collision energies (medium temperatures).

Purpose: We study the azimuthal anisotropy of jet quenching, to seek constraints on different models featuring distinct path-length and density dependences for jet energy loss, and to gain a better understanding of the medium.

Methods: The models are fixed by using the RHIC data, and then applied to study the LHC case. A set of harmonic (Fourier) coefficients $v_n$ are extracted from the jet azimuthal anisotropy on a event-by-event basis.

Results: The second harmonics $v_2$, mostly driven by the medium's geometry, can be used to differentiate jet quenching models. Other harmonics are also compared with the LHC (2.76 TeV) data. The predictions for future LHC (5.5 TeV) run are presented.

Conclusions: We find that a too strong path-length dependence (e.g., cubic) is ruled out by the LHC $v_2$ data, while the model with a strong near-$T_c$ enhancement for the jet-medium interaction describes the data very well. It is worth pointing out that the latter model expects a less color-opaque medium at LHC.

We report on an improved measurement of the $2\nu \beta \beta$ half-life of ${}^{136}$Xe performed by EXO-200. The use of a large and homogeneous time-projection chamber allows for the precise estimate of the fiducial mass used for the measurement, resulting in a small systematic uncertainty. We also discuss in detail the data-analysis methods used for double-$\beta$ decay searches with EXO-200, while emphasizing those directly related to the present measurement. The ${}^{136}$Xe $2\nu \beta \beta$ half-life is found to be $T_{1/2}^{2\nu \beta \beta }$ = $2.165\pm 0.016\left(\mathrm{stat}\right)\pm 0.059\left(\mathrm{sys}\right)\times {10}^{21}$ yr. This is the most precisely measured half-life of any $2\nu \beta \beta$ decay to date.