The ${}^{236}\mathrm{U}(n,\gamma )$ reaction cross section has been measured for the incident neutron energy range from 10 eV to 800 keV by using the Detector for Advanced Neutron Capture Experiments (DANCE) $\gamma$-ray calorimeter at the Los Alamos Neutron Science Center. The cross section was determined with the ratio method, which is a technique that uses the ${}^{235}\mathrm{U}(n,f)$ reaction as a reference. The results of the experiment are reported in the resolved and unresolved resonance energy regions. Individual neutron resonance parameters were obtained below 1 keV incident energy by using the $R$-matrix code sammy. The cross section in the unresolved resonance region is determined with improved experimental uncertainty. It agrees with both ENDF/B-VII.1 and JEFF-3.2 nuclear data libraries. The results above 10 keV agree better with the JEFF-3.2 library.

This paper reports new exclusive cross sections for $ep\to e^{\prime }{\pi }^{+}{\pi }^{-}{p}^{\prime }$ using the CLAS detector at Jefferson Laboratory. These results are presented for the first time at photon virtualities $2.0{\mathrm{GeV}}^2<Q^2<5.0{\mathrm{GeV}}^2$ in the center-of-mass energy range 1.4 GeV $<W<$ 2.0 GeV, which covers a large part of the nucleon resonance region. Using a model developed for the phenomenological analysis of electroproduction data, we see strong indications that the relative contributions from the resonant cross sections at $W<1.74$ GeV increase with $Q^2$. These data considerably extend the kinematic reach of previous measurements. Exclusive $ep\to e^{\prime }{\pi }^{+}{\pi }^{-}{p}^{\prime }$ cross section measurements are of particular importance for the extraction of resonance electrocouplings in the mass range above 1.6 GeV.

Neutron-proton pairing correlations are investigated in detail via $np$ transfer reactions in $N=Zsd$-shell nuclei. In particular, we study the cross-section ratio of the lowest $0^{+}$ and $1^{+}$ states as an observable to quantify the interplay between $T=0$ (isoscalar) and $T=1$ (isovector) pairing strengths. The experimental results are compared to second-order distorted-wave Born approximation calculations with proton-neutron amplitudes obtained in the shell-model formalism using the universal $sd$-shell interaction B. Our results suggest underestimation of the nonneglible isoscalar pairing strength in the shell-model descriptions at the expense of the isovector channel.

Static and dynamic aspects of the fission process of ${}^{226}\mathrm{Th}$ are analyzed in a self-consistent framework based on relativistic energy density functionals. Constrained relativistic mean-field calculations in the collective space of axially symmetric quadrupole and octupole deformations, based on the energy density functional PC-PK1 and a $\delta$-force pairing, are performed to determine the potential energy surface of the fissioning nucleus, the scission line, the single-nucleon wave functions, energies, and occupation probabilities, as functions of deformation parameters. Induced fission dynamics is described using the time-dependent generator coordinate method in the Gaussian overlap approximation. A collective Schrödinger equation, determined entirely by the microscopic single-nucleon degrees of freedom, propagates adiabatically in time the initial wave packet built by boosting the ground-state solution of the collective Hamiltonian for ${}^{226}\mathrm{Th}$. The position of the scission line and the microscopic input for the collective Hamiltonian are analyzed as functions of the strength of the pairing interaction. The effect of static pairing correlations on the preneutron emission charge yields and total kinetic energy of fission fragments is examined in comparison with available data, and the distribution of fission fragments is analyzed for different values of the initial excitation energy.

Evaporation-proton yields were measured for the fusion of the weakly bound nucleus ${}^6\mathrm{Li}$ on a ${}^{58}\mathrm{Ni}$ target at six near- or sub-barrier bombarding energies. Effects of the one-neutron transfer reaction were estimated and corrections made. Total-fusion cross sections were deduced using calculated proton multiplicities. The resulting fusion excitation function shows a considerable enhancement with respect to calculations for a bare potential. Inelastic couplings are estimated to have insignificant effects on such fusion. The sum of total fusion plus one-neutron transfer cross sections nearly saturates the total reaction cross section in the energy region measured. Comparison with previous results appropriately scaled for the ${}^6\mathrm{Li}+({}^{59}\mathrm{Co}, {}^{64}\mathrm{Ni}, {}^{64}\mathrm{Zn})$ systems shows good consistency except for some data spread at the lower energies.

Background: Multinucleon transfer in low-energy nucleus-nucleus collisions is proposed as a method of production of yet-unknown neutron-rich nuclei hardly reachable by other methods.

Purpose: Modeling of dynamics of nuclear reactions induced by heavy ions in their full complexity of competing reaction channels remains to be a challenging task. The work is aimed at development of such a model and its application to the analysis of multinucleon transfer in deep inelastic collisions of heavy ions leading, in particular, to formation of neutron-rich isotopes in the vicinity of the $N=126$ shell closure.

Method: Multidimensional dynamical model of nucleus-nucleus collisions based on the Langevin equations has been proposed. It is combined with a statistical model for simulation of de-excitation of primary reaction fragments. The model provides a continuous description of the system evolution starting from the well-separated target and projectile in the entrance channel of the reaction up to the formation of final reaction products.

Results: A rather complete set of experimental data available for reactions ${}^{136}\mathrm{Xe}+{}^{198}\mathrm{Pt},{}^{208}\mathrm{Pb},{}^{209}\mathrm{Bi}$ was analyzed within the developed model. The model parameters have been determined. The calculated energy, mass, charge, and angular distributions of reaction products, their various correlations as well as cross sections for production of specific isotopes agree well with the data. On this basis, optimal experimental conditions for synthesizing the neutron-rich nuclei in the vicinity of the $N=126$ shell were formulated and the corresponding cross sections were predicted.

Conclusions: The production yields of neutron-rich nuclei with $N=126$ weakly depend on the incident energy. At the same time, the corresponding angular distributions are strongly energy dependent. They are peaked at grazing angles for larger energies and extend up to the forward angles at low near-barrier collision energies. The corresponding cross sections exceed 100 nb for the nuclei located at the border of the known region, which is nearly five orders of magnitude larger than can be reached in the fragmentation reactions.

A neutron inelastic scattering experiment was performed on an enriched ${}^{57}\mathrm{Fe}$ sample at the Geel Electron Linear Accelerator neutron source using the Gamma Array for Neutron Inelastic Scattering spectrometer. Several $\gamma$-production cross sections were determined, but the first transition (14.4 keV) could not be detected owing to the steadily increased $\gamma$ background at low energies. Consequently, we use an interplay between experimental data and carefully tuned theoretical calculations to generate the total inelastic cross section.

Photoproduction of ${\mathrm{\Lambda }}^{*}\left(1520\right)$ resonance of spin-parity ${\frac{3}{2}}^{-}$ off the proton target is investigated within the Regge framework where the reggeization of the $t$-channel meson exchange is applied for the $K\left(494\right)+K^{*}\left(892\right)+K_2^{*}\left(1430\right)$ exchanges in the Born amplitude. The present model is based on two basic ingredients; one is the minimal gauge prescription for the convergence of the reaction and the other is the role of $K_2^{*}$ crucial to be consistent with high energy data. Cross sections for total, differential, and photon polarization asymmetry are reproduced without fit parameters and compared with existing data. The LAMP2 and LEPS measurements of the angular distribution of $K^{-}$ in the ${\mathrm{\Lambda }}^{*}\left(1520\right)\to K^{-}p$ decay are investigated and found to be dominated by the decay of ${\mathrm{\Lambda }}^{*}$ with helicity $\pm 3/2$ based on the analysis of the density matrix elements. Detailed discussion on the density matrix elements is given to clarify the analysis of the observable. The reaction mechanism is featured by the dominance of the contact term with $K$ and $K_2^{*}$ exchanges following in the low energy region. The $K^{*}$ exchange appears in a minor role. At high energies beyond $E_{\gamma }\approx 5$ GeV the role of $K_2^{*}$ exchange leads over other exchanges in the reaction process.

We use the Coulomb dissociation (CD) method to calculate the rate of the ${}^{36}\mathrm{Mg}\left(n,\gamma \right){}^{37}\mathrm{Mg}$ radiative capture reaction. The CD cross sections of the ${}^{37}\mathrm{Mg}$ nucleus on a ${}^{208}\mathrm{Pb}$ target at the beam energy of 244 MeV/nucleon, for which new experimental data have recently become available, were calculated within the framework of a finite-range distorted-wave Born approximation theory that is extended to include the projectile deformation effects. Invoking the principle of detailed balance, these cross sections are used to determine the excitation function and subsequently the rate of the ${}^{36}\mathrm{Mg}(n,\gamma ){}^{37}\mathrm{Mg}$ reaction. We compare these rates to those of the ${}^{36}\mathrm{Mg}(\alpha ,n){}^{39}\mathrm{Si}$ reaction calculated within a Hauser-Feshbach model. We find that for ${\mathrm{T}}_9$ as large as up to 1.0 (in units of ${10}^9$ K) the ${}^{36}\mathrm{Mg}(n,\gamma ){}^{37}\mathrm{Mg}$ reaction is much faster than the ${}^{36}\mathrm{Mg}(\alpha ,n){}^{39}\mathrm{Si}$ one. The inclusion of the effects of ${}^{37}\mathrm{Mg}$ projectile deformation in the breakup calculations enhances the ($n,\gamma$) reaction rate even further. Therefore, it is highly unlikely that the $(n,\gamma )\beta$-decay $r$-process flow will be broken at the ${}^{36}\mathrm{Mg}$ isotope by the $\alpha$ process.

We calculate the frequencies of collective modes of neutrons, protons, and electrons in the outer core of neutron stars. The neutrons and protons are treated in a hydrodynamic approximation and the electrons are regarded as collisionless. The coupling of the nucleons to the electrons leads to Landau damping of the collective modes and to significant dispersion of the low-lying modes. We investigate the sensitivity of the mode frequencies to the strength of entrainment between neutrons and protons, which is not well characterized. The contribution of collective modes to the thermal conductivity is evaluated.

Relations between the nuclear symmetry energy coefficient and its density derivatives are derived. The relations hold for a class of interactions with quadratic momentum dependence and a power-law density dependence. The structural connection between the different symmetry energy elements as obtained seems to be followed by almost all reasonable nuclear energy density functionals, both relativistic and nonrelativistic, suggesting a universality in the correlation structure. This, coupled with known values of some well-accepted constants related to nuclear matter, helps in constraining values of different density derivatives of the nuclear symmetry energy, shedding light on the isovector part of the nuclear interaction.

In the present work, the unfavored $\alpha$-decay half-lives and $\alpha$ preformation probabilities of closed-shell nuclei related to ground and isomeric states around $Z=82, N=82$ and 126 shell closures are investigated by adopting the two-potential approach from the perspective of valence nucleon (hole) and isospin asymmetry of the parent nucleus. The results indicate that $\alpha$ preformation probability has linear dependence on $N_p{N}_n$ or $N_p{N}_{n}I$, the same as the case of favored $\alpha$ decay in our previous work [X.-D. Sun et al., Phys. Rev. C 94, 024338 (2016)]. $N_p, N_n$, and $I$ represent the number of valence protons (holes), the number of valence neutrons (holes), and the isospin of the parent nucleus, respectively. Fitting the $\alpha$ preformation probability data extracted from the differences between experimental data and calculated half-lives without a shell correction, we give two linear formulas of the $\alpha$ preformation probabilities and the values of corresponding parameters. Based on the formulas and corresponding parameters, we calculate the $\alpha$-decay half-lives for those nuclei. The calculated results can well reproduce the experimental data.

ATLAS measurements of two-particle correlations are presented for $\sqrt{s}=5.02$ and 13 TeV $pp$ collisions and for $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV $p+\text{Pb}$ collisions at the LHC. The correlation functions are measured as a function of relative azimuthal angle $\mathrm{\Delta }\varphi$, and pseudorapidity separation $\mathrm{\Delta }\eta$, using charged particles detected within the pseudorapidity interval $\left|\eta \right|<2.5$. Azimuthal modulation in the long-range component of the correlation function, with $\left|\mathrm{\Delta }\eta \right|>2$, is studied using a template fitting procedure to remove a “back-to-back” contribution to the correlation function that primarily arises from hard-scattering processes. In addition to the elliptic, $\cos \left(2\mathrm{\Delta }\varphi \right)$, modulation observed in a previous measurement, the $pp$ correlation functions exhibit significant $\cos \left(3\mathrm{\Delta }\varphi \right)$ and $\cos \left(4\mathrm{\Delta }\varphi \right)$ modulation. The Fourier coefficients $v_{n,n}$ associated with the $\cos \left(n\mathrm{\Delta }\varphi \right)$ modulation of the correlation functions for $n=2–4$ are measured as a function of charged-particle multiplicity and charged-particle transverse momentum. The Fourier coefficients are observed to be compatible with $\cos \left(n\varphi \right)$ modulation of per-event single-particle azimuthal angle distributions. The single-particle Fourier coefficients $v_n$ are measured as a function of charged-particle multiplicity, and charged-particle transverse momentum for $n=2–4$. The integrated luminosities used in this analysis are, 64 ${\mathrm{nb}}^{-1}$ for the $\sqrt{s}=13$ TeV $pp$ data, 170 ${\mathrm{nb}}^{-1}$ for the $\sqrt{s}=5.02$ TeV $pp$ data, and 28 ${\mathrm{nb}}^{-1}$ for the $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV $p+\text{Pb}$ data.

The modification of hard jets in an extended static medium held at a fixed temperature is studied using three different Monte Carlo event generators: linear Boltzmann transport (LBT), modular all twist transverse-scattering elastic-drag and radiation (MATTER), and modular algorithm for relativistic treatment of heavy-ion interactions (MARTINI). Each event generator contains a different set of assumptions regarding the energy and virtuality of the partons within a jet versus the energy scale of the medium and, hence, applies to a different epoch in the space-time history of the jet evolution. Here modeling is developed where a jet may sequentially transition from one generator to the next, on a parton-by-parton level, providing a detailed simulation of the space-time evolution of medium modified jets over a much broader dynamic range than has been attempted previously in a single calculation. Comparisons are carried out for different observables sensitive to jet quenching, including the parton fragmentation function and the azimuthal distribution of jet energy around the jet axis. The effect of varying the boundary between different generators is studied and a theoretically motivated criterion for the location of this boundary is proposed. The importance of such an approach with coupled generators to the modeling of jet quenching is discussed.

Nuclear level densities (NLDs) and $\gamma$-ray strength functions ($\gamma \mathrm{SFs}$) have been extracted from particle-$\gamma$ coincidences of the ${}^{92}\mathrm{Zr}(p,p^{\prime }\gamma ){}^{92}\mathrm{Zr}$ and ${}^{92}\mathrm{Zr}(p,d\gamma ){}^{91}\mathrm{Zr}$ reactions using the Oslo method. The new ${}^{91,92}\mathrm{Zr}\gamma \mathrm{SF}$ data, combined with photonuclear cross sections, cover the whole energy range from $E_{\gamma }\approx 1.5\mathrm{MeV}$ up to the giant dipole resonance at $E_{\gamma }\approx 17$ MeV. The wide-range $\gamma \mathrm{SF}$ data display structures at $E_{\gamma }\approx 9.5$ MeV, compatible with a superposition of the spin-flip $M1$ resonance and a pygmy $E1$ resonance. Furthermore, the $\gamma \mathrm{SF}$ shows a minimum at $E_{\gamma }\approx 2–3\mathrm{MeV}$ and an increase at lower $\gamma$-ray energies. The experimentally constrained NLDs and $\gamma \mathrm{SFs}$ are shown to reproduce known ($n,\gamma$) and Maxwellian-averaged cross sections for ${}^{91,92}\mathrm{Zr}$ using the talys reaction code, thus serving as a benchmark for this indirect method of estimating ($n,\gamma$) cross sections for Zr isotopes.

This study investigated intermediate-spin states of ${}^{92}\mathrm{Zr}$ via the inverse reaction ${}^9\mathrm{Be}\left({}^{86}\mathrm{Kr},3\mathrm{n}\right){}^{92}\mathrm{Zr}$. Seven transitions were newly observed, and a lifetime was extracted for the ${10}_1^{+}$ state by analysis of Doppler-broadened line shapes of decay $\gamma$ rays. A large $B\left(E2\right)$ value was obtained for the transition from ${10}_1^{+}$ to $8_1^{+}$, and the magnitude was comparable to that for the deformed excited configurations in ${}^{94}\mathrm{Zr}$ that have recently been established. A possible origin for such collectivity is discussed qualitatively based on a phenomenological deformed rotor model. Moreover, a multipletlike structure that fits into the systematics for $N=52$ even-$A$ isotones is revealed for the negative-parity yrast states.

The structure of the ${}^{33}\mathrm{S}$ nucleus was investigated in the ${}^{24}\mathrm{Mg}({}^{14}\mathrm{N},\alpha p)$ fusion-evaporation reaction using a 40-MeV ${}^{14}\mathrm{N}$ beam. The level scheme was extended up to an excitation energy of 11.7 MeV and spin $19/2^{+}$. Lifetimes of the intermediate- and high-spin states have been investigated by the Doppler shift attenuation method. Data were compared with different shell-model calculations where effective interactions involving two main shells, the sd and the fp, are used.

In this work we present ab initio shell-model calculations for electric quadrupole moments and magnetic dipole moments of $sd$ shell nuclei using valence-space Hamiltonians derived with two ab initio approaches: the in-medium similarity renormalization group (IM-SRG) and the coupled-cluster effective interaction (CCEI). Results are in reasonable agreement with the available experimental data as well as with the results from the phenomenological USDB effective interaction. This work will add more information to the available ab initio results for the spectroscopy of $sd$ shell nuclei.

The evolution of the shape of the electron spectra of 16 forbidden ${\beta }^{-}$ decays as a function of $g_{\mathrm{A}}$ was studied using the nuclear shell model in appropriate single-particle model spaces with established, well-tested nuclear Hamiltonians. The $\beta$ spectra of ${}^{94}\mathrm{Nb}\left(6^{+}\right)\to {}^{94}\mathrm{Mo}\left(4^{+}\right)$ and ${}^{98}\mathrm{Tc}\left(6^{+}\right)\to {}^{98}\mathrm{Ru}\left(4^{+}\right)$ were found to depend strongly on $g_{\mathrm{A}}$, which makes them excellent candidates for the determination of the effective value of $g_{\mathrm{A}}$ with the spectrum-shape method (SSM). A strong $g_{\mathrm{A}}$ dependence is also seen in the spectrum of ${}^{96}\mathrm{Zr}\left(0^{+}\right)\to {}^{96}\mathrm{Nb}\left(6^{+}\right)$. This decay could be used for determining the quenching of $g_{\mathrm{A}}$ in sixth-forbidden decays in the future, when the measurement of the spectrum becomes experimentally feasible. The calculated shell-model electron spectra of the ground-state-to-ground-state decays of ${}^{87}\mathrm{Rb}$, ${}^{99}\mathrm{Tc}$, and ${}^{137}\mathrm{Cs}$ and the decay of ${}^{137}\mathrm{Cs}$ to the isomeric $11/2^{-}$ state in ${}^{137}\mathrm{Ba}$ were found to be in excellent agreement with the spectra previously calculated using the microscopic quasiparticle-phonon model. This is further evidence of the robust nature of the SSM observed in the previous studies.

The finite-amplitude method is a feasible numerical approach to large scale random phase approximation calculations. It avoids the storage and calculation of residual interaction elements as well as the diagonalization of the RPA matrix, which will be prohibitive when the configuration space is huge. In this work we finished the implementation of a finite-amplitude method in a relativistic meson exchange mean field model with axial symmetry. The direct variation approach makes our FAM scheme capable of being extended to the multipole excitation case.