Background: The variational multiparticle-multihole configuration mixing approach to nuclei has been proposed about a decade ago. While the first applications followed rapidly, the implementation of the full formalism of this method has only been recently completed and applied in C. Robin, N. Pillet, D. Peña Arteaga, and J.-F. Berger, [Phys. Rev. C 93, 024302 (2016)] to ${}^{12}\mathrm{C}$ as a test-case.

Purpose: The main objective of the present paper is to carry on the study that was initiated in that reference, in order to put the variational multiparticle-multihole configuration mixing method to more stringent tests. To that aim we perform a systematic study of even-even $sd$-shell nuclei.

Method: The wave function of these nuclei is taken as a configuration mixing built on orbitals of the $sd$-shell, and both the mixing coefficients of the nuclear state and the single-particle wave functions are determined consistently from the same variational principle. As in the previous works, the calculations are done using the D1S Gogny force.

Results: Various ground-state properties are analyzed. In particular, the correlation content and composition of the wave function as well as the single-particle orbitals and energies are examined. Binding energies and charge radii are also calculated and compared to experiment. The description of the first excited state is also examined and the corresponding transition densities are used as input for the calculation of reaction processes such as inelastic electron and proton scattering. Special attention is paid to the effect of the optimization of the single-particle states consistently with the correlations of the system.

Conclusions: The variational multiparticle-multihole configuration mixing approach is systematically applied to the description of even-even $sd$-shell nuclei. Globally, the results are satisfying and encouraging. In particular, charge radii and excitation energies are nicely reproduced. However, the chosen valence-space truncation scheme precludes achieving maximum collectivity in the studied nuclei. Further refinement of the method and a better-suited interaction are necessary to remedy this situation.

Predictions for the interaction part of the symmetry energy obtained from microscopic approaches based upon different foundations are reviewed and discussed in the light of recent updated constraints obtained from reaction observables in the ASY-EOS experiment at GSI. The discussion is then extended to the neutron skin thickness in ${}^{208}\mathrm{Pb}$ and its relation to the density derivatives of the symmetry energy at and below saturation density. With regard to the latter, the main point is to demonstrate the importance of proper consideration of the theoretical uncertainties of microscopic predictions in order to guide phenomenological analyses.

We study phenomenologically the production of the neutron-rich hypernucleus ${}_{\mathrm{\Lambda }}{}^6\mathrm{H}$ in the ${}^6\mathrm{Li}({\pi }^{-},K^{+})$ reaction at 1.2 GeV/$c$, using a distorted-wave impulse approximation in a one-step mechanism, ${\pi }^{-}p\to K^{+}{\mathrm{\Sigma }}^{-}$ via ${\mathrm{\Sigma }}^{-}$ doorways caused by ${\mathrm{\Sigma }}^{-}p\leftrightarrow \mathrm{\Lambda }n$ coupling. The production cross section of ${}_{\mathrm{\Lambda }}{}^6\mathrm{H}\left(1_{\mathrm{exc}.}^{+}\right)$ is evaluated by a coupled $({}^5\mathrm{H}-\mathrm{\Lambda })+({}^5\mathrm{He}-{\mathrm{\Sigma }}^{-})$ model with a spreading potential, in comparison with the data of the missing mass spectrum at the J-PARC E10 experiment. The result indicates that the ${\mathrm{\Sigma }}^{-}$ mixing probabilities in ${}_{\mathrm{\Lambda }}{}^6\mathrm{H}\left(1_{\mathrm{exc}.}^{+}\right)$ are $P_{{\mathrm{\Sigma }}^{-}}<\sim 0.2\%$ both for $s_{\mathrm{\Sigma }}$ state and for $p_{\mathrm{\Sigma }}$ state in order to reproduce no significant peak in the $\mathrm{\Lambda }$ production data, so that the cross section of ${}_{\mathrm{\Lambda }}{}^6\mathrm{H}$ is less than on the order of 0.4 nb/sr. The sensitivity of the $\mathrm{\Sigma }\mathrm{\Lambda }$ coupling and $\mathrm{\Lambda }$ potentials to the near-$\mathrm{\Lambda }$-threshold spectrum is discussed. The shape and magnitude of the spectrum provide valuable information on the $\mathrm{\Sigma }\mathrm{\Lambda }$ coupling in the production mechanism and also the nuclear structure of ${}_{\mathrm{\Lambda }}{}^6\mathrm{H}\left(1_{\mathrm{exc}.}^{+}\right)$.

The PHENIX experiment at the BNL Relativistic Heavy Ion Collider recently reported transverse single-spin asymmetry, $A_N$, for forward neutrons in $p^{\uparrow }A$ collisions at $\sqrt{s_{{}_{NN}}}=200\mathrm{GeV}$. $A_N$ in $p^{\uparrow }\mathrm{Al}$ and $p^{\uparrow }\mathrm{Au}$ collisions were measured as $-0.015$ and 0.18, respectively. These values are clearly different from the measured $A_N=-0.08$ in $p^{\uparrow }p$ collisions. In this paper, I propose that a large $A_N$ for forward neutrons in ultraperipheral $p^{\uparrow }A$ collisions may explain the PHENIX measurements. The proposed model is demonstrated using two Monte Carlo simulations. In the ultraperipheral collision simulation, I use the starlight event generator for the simulation of the virtual photon flux and then use the maid2007 unitary isobar model for the simulation of neutron production in the interactions of a virtual photon with a polarized proton. In the $p^{\uparrow }A$ hadronic interaction simulation, the differential cross sections for forward neutron production are predicted by a simple one-pion exchange model and the Glauber model. The simulated $A_N$ values for both the contribution of ultraperipheral collisions and the hadronic interactions are in good agreement with the PHENIX results.

Tensor-optimized antisymmetrized molecular dynamics (TOAMD) is the basis of the successive variational method for the nuclear many-body problem. We apply TOAMD to finite nuclei described by the central interaction with strong short-range repulsion, and compare the results with those from the unitary correlation operator method (UCOM). In TOAMD, the pair-type correlation functions and their multiple products are operated to the antisymmetrized molecular dynamics (AMD) wave function. We show the results of TOAMD using the Malfliet-Tjon central potential containing the strong short-range repulsion. By adding the double products of the correlation functions in TOAMD, the binding energies are converged quickly to the exact values of the few-body calculations for $s$-shell nuclei. This indicates the high efficiency of TOAMD for treating the short-range repulsion in nuclei. We also employ the $s$-wave configurations of nuclei with the central part of UCOM, which reduces the short-range relative amplitudes of nucleon pair in nuclei to avoid the short-range repulsion. In UCOM, we further perform the superposition of the $s$-wave configurations with various size parameters, which provides a satisfactory solution of energies close to the exact and TOAMD values.

Production cross sections of ${}^{209}\mathrm{Bi}(p, xn){}^{207,206,205,204,203}\mathrm{Po}, {}^{209}\mathrm{Bi}(p$, pxn)${}^{207,206,205,204,203,202}\mathrm{Bi}$, and ${}^{\mathrm{nat}}\mathrm{Pb}(p, xn$) ${}^{206,205,204,203,202,201}\mathrm{Bi}$ reactions were measured to fill the gap in the excitation functions up to 100 MeV as well as to figure out the effects of different nuclear properties on proton-induced reactions including heavy nuclei. The targets were arranged in two different stacks consisting of Bi, Pb, Al, Au foils and Pb plates. The proton beam intensity was determined by the activation analysis method using ${}^{27}\mathrm{Al}\left(p,3pn\right){}^{24}\mathrm{Na}, {}^{197}\mathrm{Au}\left(p,pn\right){}^{196}\mathrm{Au}$, and ${}^{197}\mathrm{Au}(p, p3n){}^{194}\mathrm{Au}$ monitor reactions in parallel as well as the Gafchromic film dosimetry method. The activities of produced radionuclei in the foils were measured by the HPGe spectroscopy system. Over 40 new cross sections were measured in the investigated energy range. A satisfactory agreement was observed between the present experimental data and the previously published data. Excitation functions of mentioned reactions were calculated by using the theoretical model based on the latest version of the TALYS code and compared to the new data as well as with other data in the literature. Additionally, the effects of various combinations of the nuclear input parameters of different level density models, optical model potentials, and γ-ray strength functions were considered. It was concluded that if certain level density models are used, the calculated cross sections could be comparable to the measured data. Furthermore, the effects of optical model potential and γ-ray strength functions were considerably lower than that of nuclear level densities.

We discuss the possible factorization of the tensor asymmetry $A_d^T$ measured for polarized deuteron targets within a relativistic framework. We define a reduced asymmetry and find that factorization holds only in plane wave impulse approximation and if $p$ waves are neglected. Our numerical results show a strong factorization breaking once final state interactions are included. We also compare the $d$-wave content of the wave functions with the size of the factored, reduced asymmetry and find that there is no systematic relationship of this quantity to the $d$-wave probability of the various wave functions.

The polarization of direct photons produced in an ultrarelativistic heavy-ion collision reflects the momentum anisotropy of the quark-gluon plasma created in the collision. This paper presents a general framework, based on the photon spectral functions in the plasma, for analyzing the angular distribution and thus the polarization of dileptons in terms of the plasma momentum anisotropies. The rates of dilepton production depend, in general, on four independent spectral functions, corresponding to two transverse polarizations, one longitudinal polarization, and—in plasmas in which the momentum anisotropy is not invariant under parity in the local rest frame of the matter—a new spectral function, ${\rho }_n$, related to the anisotropy direction in the collision. The momentum anisotropy appears in the difference of the two transverse spectral functions, as well as in ${\rho }_n$. As an illustration, we delineate the spectral functions for dilepton pairs produced in the lowest order Drell-Yan process of quark-antiquark annihilation to a virtual photon.

Electron capture can determine the electron neutrino mass, while the $\beta$ decay of tritium measures the electron antineutrino mass and the neutrinoless double $\beta$ decay observes the Majorana neutrino mass. In electron capture, e.g., ${}_{67}{}^{163}\mathrm{Ho}+e^{-}\to \stackrel{*}{{}_{66}{}^{163}\mathrm{Dy}}+{\nu }_e$, one can determine the electron neutrino mass from the upper end of the decay spectrum of the excited Dy, which is given by the $Q$ value minus the neutrino mass. The excitation of Dy is described by one, two, and even three hole excitations limited by the $Q$ value. These states decay by x-ray and Auger electron emissions. The total decay energy is measured in a bolometer. These excitations have been studied by Robertson and by Faessler et al. In addition the daughter atom Dy can also be excited by moving in the capture process one (or more) electrons into the continuum. The escape of these continuum electrons is automatically included in the experimental bolometer spectrum. Recently a method developed by Intemann and Pollock was used by DeRujula and Lusignoli for a rough estimate of this shake-off process for “$s$” wave electrons in capture on ${}^{163}\mathrm{Ho}$. The purpose of the present work is to give a more reliable description of “$s$” wave shake-off in electron capture on holmium. One uses the sudden approximation to calculate the spectrum of the decay of $\stackrel{*}{{}_{66}{}^{163}\mathrm{Dy}}$ after electron capture on ${}_{67}{}^{163}\mathrm{Ho}$. For that one needs very accurate atomic wave functions of Ho in its ground state and excited atomic wave functions of Dy including a description of the continuum electrons. DeRujula and Lusignoli use screened nonrelativistic Coulomb wave functions for the Ho electrons $3s$ and $4s$ and calculate the Dy* states by first-order perturbation theory based on Ho. In the present approach the wave functions of Ho and Dy* are determined self-consistently with the antisymmetrized relativistic Dirac-Hartree-Fock approach. The relativistic continuum electron wave functions for the ionized Dy* are obtained in the corresponding self-consistent Dirac-Hartree-Fock potential. The result of this improved approach is that shake-off can hardly be seen in the bolometer spectrum after electron capture in ${}^{163}\mathrm{Ho}$ and thus can probably not affect the determination of the electron neutrino mass.

The two odd-even fluorine isotopes ${}^{27,29}\mathrm{F}$ were studied via in-beam $\gamma$-ray spectroscopy at the RIKEN Radioactive Isotope Beam Factory. A secondary beam of ${}^{30}\mathrm{Ne}$ was used to induce one-proton and one-proton–two-neutron removal reactions on carbon and polyethylene targets at midtarget energies of 228 MeV/$u$. Excited states were observed at 915(12) keV for ${}^{27}\mathrm{F}$ and at 1080(18) keV for ${}^{29}\mathrm{F}$. Both were assigned a $1/2_1^{+}$ spin and parity. The low transition energy for ${}^{29}\mathrm{F}$ largely disagrees with shell model predictions restricted to the $sd$ model space. Calculations using effective interactions that include the neutron $pf$ shell indicate that the $N=20$ gap is quenched for ${}^{29}\mathrm{F}$, thus extending the “island of inversion” to isotopes with proton number $Z=9$. Variations of the $N=20$ gap further reveal a strong correlation to the $1/2_1^{+}$ level energy in ${}^{29}\mathrm{F}$ and suggest a persistent reduced neutron gap for ${}^{28}\mathrm{O}$.

The reaction ${}^{58}\mathrm{Ni}+{}^{238}\mathrm{U}$ is investigated within the framework of dinuclear system model. The incident energy effects on production cross sections of actinide nuclei are studied. It is found that the optimal incident energies for producing neutron-deficient isotopes are larger than those for production of neutron-rich ones, and for producing neutron-deficient isotopes the optimal incident energies strongly depend on neutron richness of objective products.

Based on a covariant coalescence model with a blast-wave-like parametrization for the phase-space configuration of constituent particles at freeze-out, we derive an approximate analytical formula for the yields of clusters produced in relativistic heavy-ion collisions. Compared to previous formulas, the present work additionally considers the contributions from the longitudinal dimension in momentum space, the relativistic corrections, and the finite-size effects of the produced clusters relative to the spatial distribution of constituent particles at freeze-out. The new analytical coalescence formula provides a useful tool to evaluate the yield of produced clusters, such as light nuclei from nucleon coalescence and hadrons from quark coalescence, in heavy-ion collisions. As a first application of the new analytical formula, we explore the strangeness population factor $S_3={}_{\mathrm{\Lambda }}^3\mathrm{H}$/(${}^3\mathrm{He}\times \mathrm{\Lambda }/p$) based on nucleon/$\mathrm{\Lambda }$ coalescence as well as the production of exotic hadrons based on quark coalescence, in central Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV. The results are compared with the predictions from other models.

In this paper we report the effect of the jet-medium interplay as implemented in the EPOS 3 model on the ridgelike structure observed in high-multiplicity $p$-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV. EPOS 3 takes into account hydrodynamically expanding bulk matter, jets and the jet-medium interaction. The basis of this model is multiple scatterings where each scattering finally produces flux tubes (strings). In the higher multiplicity event classes where the density of flux-tubes (strings) is higher, there is a finite probability that the strings will pick up quarks and antiquarks (or diquarks) from the bulk (core) for flux-tube breaking to produce jet hadrons (corona) instead of producing them via the usual Schwinger mechanism. This will eventually create a correlation between core and corona and also influence the corona-corona correlation because the corona particles containing quarks and antiquarks (or diquarks) from the bulk also carry the fluid information. We report the relative contributions of the core-core, core-corona, corona-core, and corona-corona correlations toward the ridge in high- and low-multiplicity $p$-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV using the data generated by EPOS 3. The multiplicity evolution of the ridges in all the cases is also reported.

Background: The origin of fluorine is a widely debated issue. Nevertheless, the ${}^{15}\mathrm{N}(\alpha ,\gamma ){}^{19}\mathrm{F}$ reaction is a common feature among the various production channels so far proposed. Its reaction rate at relevant temperatures is determined by a number of narrow resonances together with the direct capture and the tails of the two broad resonances at $E_{\mathrm{c}.\mathrm{m}.}=1323$ and 1487 keV.

Purpose: The broad resonances widths, ${\mathrm{\Gamma }}_{\gamma }$ and ${\mathrm{\Gamma }}_{\alpha }$, have to be measured with adequate precision in order to better determine their contribution to the ${}^{15}\mathrm{N}(\alpha ,\gamma ){}^{19}\mathrm{F}$ stellar reaction rate.

Methods: Measurement through the direct detection of the ${}^{19}\mathrm{F}$ recoil ions with the European Recoil separator for Nuclear Astrophysics (ERNA) were performed. The reaction was initiated by a ${}^{15}\mathrm{N}$ beam impinging onto a ${}^4\mathrm{He}$ windowless gas target. The observed yield of the resonances at $E_{\mathrm{c}.\mathrm{m}.}=1323$ and 1487 keV is used to determine their widths in the $\alpha$ and $\gamma$ channels.

Results: We show that a direct measurement of the cross section of the ${}^{15}\mathrm{N}(\alpha ,\gamma ){}^{19}\mathrm{F}$ reaction can be successfully obtained with the recoil separator ERNA, and the widths ${\mathrm{\Gamma }}_{\gamma }$ and ${\mathrm{\Gamma }}_{\alpha }$ of the two broad resonances have been determined. While a fair agreement is found with earlier determination of the widths of the 1487 keV resonance, a significant difference is found for the 1323 keV resonance ${\mathrm{\Gamma }}_{\alpha }$.

Conclusions: The revision of the widths of the two more relevant broad resonances in the ${}^{15}\mathrm{N}(\alpha ,\gamma ){}^{19}\mathrm{F}$ reaction presented in this work is the first step toward a more firm determination of the reaction rate. At present, the residual uncertainty at the temperatures of the ${}^{19}\mathrm{F}$ stellar nucleosynthesis is dominated by the uncertainties affecting the direct capture component and the 364 keV narrow resonance, both so far investigated only through indirect experiments.

Nuclear fission is hindered by dissipation. Based on the stochastic Langevin model, we calculate the drop of fission cross section caused by friction with respect to its standard statistical-model value, ${\sigma }_f^{\mathrm{drop}}$, as a function of the presaddle friction strength ($\beta$) for fissioning nuclei ${}^{205}\mathrm{Bi}$, ${}^{215}\mathrm{Fr}$, ${}^{225}\mathrm{Pa}$, and ${}^{230}\mathrm{Np}$ at different angular momenta and excitation energies. It is found that with increasing the size of fissioning systems, the sensitivity of ${\sigma }_f^{\mathrm{drop}}$ to $\beta$ is reduced substantially, and it disappears for the ${}^{230}\mathrm{Np}$ system. Our findings suggest that on the experimental side, to more stringently constrain the presaddle dissipation strength by measuring fission excitation functions, it is optimal to yield those fissioning systems with a small size.

Evolution of the electron spectra with the effective value of the weak axial-vector coupling constant $g_{\mathrm{A}}$ was followed for 26 first-, second-, third-, fourth- and fifth-forbidden ${\beta }^{-}$ decays of odd-$A$ nuclei by calculating the involved nuclear matrix elements (NMEs) in the framework of the microscopic quasiparticle-phonon model (MQPM). The next-to-leading-order terms were included in the $\beta$-decay shape factor of the electron spectra. The spectrum shapes of third- and fourth-forbidden nonunique decays were found to depend strongly on the value of $g_{\mathrm{A}}$, while first- and second-forbidden decays were mostly unaffected by the tuning of $g_{\mathrm{A}}$. The $g_{\mathrm{A}}$-driven evolution of the normalized $\beta$ spectra was found to be quite universal, largely insensitive to the small changes in the nuclear mean field and the adopted residual many-body Hamiltonian producing the excitation spectra of the MQPM. This makes the comparison of experimental and theoretical electron spectra, coined “the spectrum-shape method” (SSM), a robust tool for extracting information on the effective values of the weak coupling constants. In this exploratory work two new experimentally interesting decays for the SSM treatment were discovered: the ground-state-to-ground-state decays of ${}^{99}\mathrm{Tc}$ and ${}^{87}\mathrm{Rb}$. Comparing the experimental and theoretical spectra of these decays could shed light on the effective values of $g_{\mathrm{A}}$ and $g_{\mathrm{V}}$ for second- and third-forbidden nonunique decays. The measurable decay transitions of ${}^{135}\mathrm{Cs}$ and ${}^{137}\mathrm{Cs}$, in turn, can be used to test the SSM in different many-body formalisms. The present work can also be considered as a (modest) step towards solving the $g_{\mathrm{A}}$ problem of the neutrinoless double beta decay.

The accurate determination of the maximum mass of the neutron stars is one of the most important tasks in astrophysics. It is directly related to the identification of the black holes in the universe, the production of neutron stars from the supernovae explosion, and the equation of state (EoS) of dense matter. However, not only the EoS is directly connected with neutron star masses, but also the speed of sound in dense matter is a crucial quantity which characterizes the stiffness of the EoS. The upper bound of the speed of sound imposes strong constraints on the maximum mass of neutron stars. However, this upper bound remains still an open issue. Recent observations, of binary neutron star systems, offer the possibility of measuring with high accuracy both the mass and the tidal polarizability of the stars. We study possible effects of the upper bound of the speed of sound on the upper bound of the mass and the tidal polarizability. We conclude that these kinds of measurements, combined with recent observations of neutron stars with masses close to $2M_{\odot }$, will provide robust constraints on the equation of state of hadronic matter at high densities.

The Vlasov equation is used to determine the dispersion relation for the eigenmodes of magnetized nuclear and neutral stellar matter, taking into account the anomalous magnetic moment of nucleons. The formalism is applied to the determination of the dynamical spinodal section, a quantity that gives a good estimation of the crust-core transition in neutron stars. We study the effect of strong magnetic fields, of the order of ${10}^{15}–{10}^{17}$ G, on the extension of the crust of magnetized neutron stars. The dynamical instability region of neutron-proton-electron ($npe$) matter at subsaturation densities is determined within a relativistic mean-field model. It is shown that a strong magnetic field has a large effect on the instability region, defining the crust-core transition as a succession of stable and unstable regions due to the opening of new Landau levels. The effect of the anomalous magnetic moment is non-negligible for fields larger than ${10}^{15}$ G. The complexity of the crust at the transition to the core and the increase of the crust thickness may have direct impact on the properties of neutrons stars related with the crust.