The equation of state (EOS) of dense matter is an essential ingredient for numerical simulations of core-collapse supernovae and neutron star mergers. The properties of matter near and above nuclear saturation density are uncertain, which translates into uncertainties in astrophysical simulations and their multimessenger signatures. Therefore, a wide range of EOSs spanning the allowed range of nuclear interactions are necessary for determining the sensitivity of these astrophysical phenomena and their signatures to variations in input microphysics. We present a new set of finite temperature EOSs based on experimentally allowed Skyrme forces. We employ a liquid-drop model of nuclei to capture the nonuniform phase of nuclear matter at subsaturation density, which is blended into a nuclear statistical equilibrium EOS at lower densities. We also provide a new, open-source code for calculating EOSs for arbitrary Skyrme parametrizations. We then study the effects of different Skyrme parametrizations on thermodynamical properties of dense astrophysical matter, the neutron star mass-radius relationship, and the core collapse of 15 and 40 solar mass stars.

In order to study the $T_z=+1\to 0$ Gamow-Teller (GT) transitions in the mass $A=26$ system, a charge-exchange reaction ${}^{26}\mathrm{Mg}({}^3\mathrm{He},t){}^{26}\mathrm{Al}$ was performed at an incident energy of 140 MeV/nucleon and scattering angle at and near $0^{\circ }$, where $T_z$ is the $z$ component of isospin $T$ defined by $(N-Z)/2$. In this ($p,n$)-type reaction, it is expected that GT states with $T=0$, 1, and 2 are excited. An energy resolution of $\mathrm{\Delta }E=23$ keV allowed us to study many discrete states. Most of the prominent states showed $0^{\circ }$-peaked angular distributions, which suggested that they are the states excited by $\mathrm{\Delta }L=0$ GT transitions. Candidates of GT states were studied up to an excitation energy $E_x=18.5$ MeV. The reduced GT transition strengths, $B\left(\mathrm{GT}\right)$, were derived assuming the proportionality between cross sections and $B\left(\mathrm{GT}\right)$ values. Standard $B\left(\mathrm{GT}\right)$ values were obtained form the ${}^{26}\mathrm{Si}\beta$ decay, where the mirror symmetry of $T_z=\pm 1\to 0$ GT transitions was assumed. The GT strength, as a whole, is divided in two energy regions: the region of up to 8.5 MeV and the higher-energy region of $8.5\text{–}12.8$ MeV, where the strength in the latter region distributed like a resonance. The obtained GT strength distribution is compared with the results of random phase approximation calculations. The $T=2$ GT states are expected in the region $E_x\ge 13.5$ MeV. By comparing with the results of ($n,p$)-type ${}^{26}\mathrm{Mg}(d,{}^2\mathrm{He}){}^{26}\mathrm{Na}$ and ${}^{26}\mathrm{Mg}(t,{}^3\mathrm{He}){}^{26}\mathrm{Na}$ reactions, the isospin symmetry of $T=2$ GT states is discussed. Owing to the high-energy resolution, we could study the decay widths $\mathrm{\Gamma }$ for the states in the $E_x>9$ MeV region. The $T=2$ state at 13.592 MeV is not noticeably wider than the experimental energy resolution. The narrow width of the state is explained in terms of isospin selection rules.

It is well known that the observables in a single-channel scattering problem remain invariant once the amplitude is multiplied by an overall energy- and angle-dependent phase. This invariance is called the continuum ambiguity and acts on the infinite partial-wave set. It has also long been known that, in the case of a truncated partial wave set, another invariance exists, originating from the replacement of the roots of partial-wave amplitudes with their complex conjugate values. This discrete ambiguity is also known as the Omelaenko-Gersten-type ambiguity. In this paper, we show that for scalar particles, discrete ambiguities are just a subset of continuum ambiguities with a specific phase and thus mix partial waves, as the continuum ambiguity does. We present the main features of both continuum and discrete ambiguities and describe a numerical method which establishes the relevant phase connection.

All deuteron analyzing powers for elastic deuteron-proton ($dp$) scattering have been measured with a polarized deuteron beam at 186.6 MeV/nucleon. They are compared with results of three-nucleon Faddeev calculations based on the standard, high-precision nucleon-nucleon ($NN$) potentials alone or combined with commonly used three-nucleon force ($3N\mathrm{F}$) models such as the Tucson-Melbourne '99 or the Urbana IX. Predicted $3N\mathrm{F}$ effects localized at backward angles are supported only partially by the data. The data are also compared to predictions based on locally regularized chiral $NN$ potentials. An estimation of theoretical truncation uncertainties in the consecutive orders of chiral expansion suggests that the observed discrepancies between this modern theory and the data could probably be explained by including chiral $3N\mathrm{F}$'s in future calculations. A systematic comparison to the deuteron analyzing power data previously taken at incident energies from 70 to 294 MeV/nucleon clearly shows that not only the cross section but also the analyzing powers reveal growing $3N\mathrm{F}$ effects when the three-nucleon system energy is increased.

The excited states of the proton emitter ${}^{151}\mathrm{Lu}$ were reinvestigated in a recoil-decay tagging experiment at the Accelerator Laboratory of the University of Jyväskylä (JYFL). The level scheme built on the ground state of ${}^{151}\mathrm{Lu}$ was updated with five new $\gamma$-ray transitions. Large-scale shell model calculations were carried out in the model space consisting of the neutron and proton orbitals $0g_{7/2}$, $1d_{5/2}$, $1d_{3/2}$, $2s_{1/2}$, and $0h_{11/2}$ with the optimized monopole interaction in order to interpret the experimental level scheme of ${}^{151}\mathrm{Lu}$. It is found that the excitation energies of states above the $27/2^{-}$ and $23/2^{+}$ isomeric levels in ${}^{151}\mathrm{Lu}$ can be sensitive to excitations from $g_{7/2}$ and $d_{5/2}$ to single-particle orbitals above $N=Z=64$.

We study the structure and decay properties of triaxially deformed odd-$A$ proton emitter ${}^{147,147\text{m}}\mathrm{Tm}$ with the modified particle-rotor model, which utilizes the microscopic nonadiabatic quasiparticle approach. In this approach the core spectrum is coupled with the particle states and hence the rotor properties are carried forward to the odd-$A$ system. We demonstrate the merits of this approach by explaining the measured rotational bands in the triaxial proton emitters ${}^{141}\mathrm{Ho}$ and ${}^{145,147}\mathrm{Tm}$. With our calculated spectra and half-lives for the proton emission, we confirm the ground state of ${}^{147}\mathrm{Tm}$ to be $11/2^{-}$ and predict the positive parity isomeric state to be $5/2^{+}$.

Thermal and transport properties of hot nuclear matter formed in central ${}^{129}\mathrm{Xe}+{}^{119}\mathrm{Sn}$ collisions at the Fermi energy are investigated using the isospin-dependent quantum molecular dynamical model. Temperature ($T$), average density ($\rho$), chemical potential ($\mu$), mean momentum ($P$), shear viscosity ($\eta$), and entropy density ($s$) are obtained from the phase-space information. The mean free path (${\lambda }_{nn}$) and the in-medium nucleon-nucleon cross section (${\sigma }_{nn}$) in the highest compressible stage at different incident energies are deduced and compared with the experimental results from Phys. Rev. C 90, 064602 (2014). The result shows that ${\lambda }_{nn}$ and ${\sigma }_{nn}$ have the same trend and similar values as the experimental results when the beam energy is greater than 40 MeV/nucleon at maximum compressed state. Furthermore, the derived shear viscosity over entropy density ($\eta /s$) shows a decreasing behavior to a saturated value around $\frac{3}{4\pi }$ as a function of incident energy.

The nuclear medium effect in $\alpha$ decay is introduced into the microscopic double-folding model to construct an improved $\alpha$-nucleus potential. Under the local density approximation, the $\alpha$-cluster density distribution is considered to vary with the surrounding matter density as a result of the medium effect. The density-dependence of the $\alpha$ cluster is incorporated by the width parameter of the Gaussian function and constrained by the critical features derived from previous microscopic studies. The influence of the medium effect to the geometry of the $\alpha$-nucleus potential is studied by comparing with the conventional double-folding potential. To examine the improved potential, the $\alpha$-decay half-lives and preformation factors of even-even spherical nuclei are calculated and compared with experimental data. With the $\alpha$-decay data being well explained, it is concluded that the inclusion of the nuclear medium effect contributes to an improved double-folding $\alpha$-nucleus potential, which incorporates more details of the $\alpha$-decay process.

Experimental data on Coulomb breakup and neutron removal indicate that ${}^{31}\mathrm{Ne}$ is one of the heaviest halo nuclei discovered so far. The possible ground state of ${}^{31}\mathrm{Ne}$ is either $3/2^{-}$ coming from the $p$-wave halo or $1/2^{+}$ coming from the $s$-wave halo. In this work, we develop a treatable model to include deformed wave functions and a dynamical knockout formalism that includes the dependence on the nuclear orientation to study the neutron removal from ${}^{31}\mathrm{Ne}$ projectiles at energies around $E\approx 200$ MeV/nucleon. A detailed account of the effects of deformation on cross sections and longitudinal momentum distributions is made. Our numerical analysis indicates a preference for the ${}^{31}\mathrm{Ne}$ ground state with spin-parity $3/2^{-}$.

For the first time a principle-component analysis is used to separate out different orthogonal modes of the two-particle correlation matrix from heavy ion collisions. The analysis uses data from $\sqrt{s_{{}_{NN}}}=2.76\text{TeV}$ PbPb and $\sqrt{s_{{}_{NN}}}=5.02\text{TeV}$ $p\text{Pb}$ collisions collected by the CMS experiment at the CERN Large Hadron Collider. Two-particle azimuthal correlations have been extensively used to study hydrodynamic flow in heavy ion collisions. Recently it was shown that the expected factorization of two-particle results into a product of the constituent single-particle anisotropies is broken. The new information provided by these modes may shed light on the breakdown of flow factorization in heavy ion collisions. The first two modes (“leading” and “subleading”) of two-particle correlations are presented for elliptical and triangular anisotropies in PbPb and $p\text{Pb}$ collisions as a function of $p_{\mathrm{T}}$ over a wide range of event activity. The leading mode is found to be essentially equivalent to the anisotropy harmonic previously extracted from two-particle correlation methods. The subleading mode represents a new experimental observable and is shown to account for a large fraction of the factorization breaking recently observed at high transverse momentum. The principle-component analysis technique was also applied to multiplicity fluctuations. These also show a subleading mode. The connection of these new results to previous studies of factorization is discussed.

Background: The interacting boson model has been used extensively to calculate the matrix elements governing neutrinoless double-$\beta$ decay. Studies within other models—the shell model, the quasiparticle random-phase approximation, and nuclear energy-density functional theory—indicate that a good description of neutron-proton pairing is essential for accurate calculations of those matrix elements, even though the isotopes used in experiment have significantly more neutrons than protons. The usual interacting boson model is based only on like-particle pairs, however, and the extent to which it captures neutron-proton pairing is not clear.

Purpose: To determine whether neutron-proton pairing should be explicitly included as neutron-proton bosons in interacting-boson-model calculations of neutrinoless double-$\beta$ decay matrix elements. In this paper we restrict ourselves to nuclei in the lower half of the $pf$ shell, where exact shell model calculations are possible.

Method: An isospin-invariant version of the nucleon-pair shell model is applied to carry out shell-model calculations in a large space and in a collective subspace, and to define effective operators in the latter. A democratic mapping is then used to define corresponding boson operators for the interacting boson model, with and without an isoscalar neutron-proton pair boson.

Results: Interacting-boson-model calculations with and without the isoscalar boson are carried out for nuclei near the beginning of the $pf$ shell, with a realistic shell-model Hamiltonian and neutrinoless double-$\beta$-decay operator as the starting point. Energy spectra and double-$\beta$ matrix elements are compared to those obtained in the underlying shell model.

Conclusions: The isoscalar boson is not important for energy spectra but improves the results for the double-$\beta$ matrix elements. To be useful at the level of precision we need, the mapping procedure must be further developed to better determine the dependence of the boson Hamiltonian and decay operator on particle number and isospin, and extended to heavier nuclei. The benefits provided by the isoscalar boson in the nuclei examined here, however, suggest that through an appropriate combination of mappings and fitting, it would make interacting-boson-model matrix elements more accurate in the heavier nuclei used in experiments.

We extract the matter root-mean-square (rms) radii of a wide range of light proton and neutron rich nuclear isotopes (He–Mg) by studying their interaction cross sections (${\sigma }_I$) on ${}^{12}\mathrm{C}$ at intermediate energies within the framework of the Glauber model. The calculations involve the nucleon densities obtained from harmonic-oscillator Slater determinants. The matter rms radii so obtained are compared with those available in the literature. It is demonstrated that the present description of matter densities can be conveniently used to explain the experimental values of ${\sigma }_I$, and the extracted matter rms radii may be considered an indication of the presence of halos and skins in proton- and neutron-rich nuclei.

The fraction of $J/\psi$ mesons which come from $B$-meson decay, ${\mathrm{F}}_{B\to J/\psi }$, is measured for $\mathrm{J}/\psi$ rapidity $1.2<\left|y\right|<2.2$ and $p_T>0$ in $p+p$ and Cu+Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV with the PHENIX detector. The extracted fraction is ${\mathrm{F}}_{B\to J/\psi }=0.025\pm 0.006$ (stat) $\pm$ 0.010(syst) for $p+p$ collisions. For Cu+Au collisions, ${\mathrm{F}}_{B\to J/\psi }$ is 0.094 $\pm$ 0.028(stat) $\pm$ 0.037(syst) in the Au-going direction ($-2.2<y<-1.2$) and 0.089 $\pm$ 0.026(stat) $\pm$ 0.040(syst) in the Cu-going direction ($1.2<y<2.2$). The nuclear modification factor, $R_{\mathrm{CuAu}}$, of $B$ mesons in Cu+Au collisions is consistent with binary scaling of measured yields in $p+p$ at both forward and backward rapidity.

We report the first measurement of differential and total cross sections for the $\gamma d\to K^0\mathrm{\Lambda }\left(p\right)$ reaction, using data from the CLAS detector at the Thomas Jefferson National Accelerator Facility. Data collected during two separate experimental runs were studied with photon-energy coverage 0.8–3.6 GeV and 0.5– 2.6 GeV, respectively. The two measurements are consistent giving confidence in the method and determination of systematic uncertainties. The cross sections are compared with predictions from the KAON-MAID theoretical model (without kaon exchange), which deviate from the data at higher $W$ and at forward kaon angles. These data, along with previously published cross sections for $K^{+}\mathrm{\Lambda }$ photoproduction, provide essential constraints on the nucleon resonance spectrum. A first partial wave analysis was performed that describes the data without the introduction of new resonances.

A superconductor of paired protons is thought to form in the core of neutron stars soon after their birth. Minimum energy conditions suggest magnetic flux is expelled from the superconducting region due to the Meissner effect, such that the neutron star core is largely devoid of magnetic fields for some nuclear equation of state and proton pairing models. We show via neutron star cooling simulations that the superconducting region expands faster than flux is expected to be expelled because cooling timescales are much shorter than timescales of magnetic field diffusion. Thus magnetic fields remain in the bulk of the neutron star core for at least ${10}^6\text{–}{10}^7\text{yr}$. We estimate the size of flux free regions at ${10}^7\text{yr}$ to be $\lesssim 100\text{m}$ for a magnetic field of ${10}^{11}\text{G}$ and possibly smaller for stronger field strengths. For proton pairing models that are narrow, magnetic flux may be completely expelled from a thin shell of approximately the above size after ${10}^5\text{yr}$. This shell may insulate lower conductivity outer layers, where magnetic fields can diffuse and decay faster, from fields maintained in the highly conducting deep core.

Excited states in ${}^{147}\mathrm{La}$, populated in spontaneous fission of ${}^{252}\mathrm{Cf}$, have been reinvestigated by means of $\gamma$-ray spectroscopy, using high-fold $\gamma$-ray coincidences measured with the Gammasphere array of Ge detectors. The 229.5-keV level, which has been assigned spin parity $9/2^{-}$ in a recent evaluation, is shown to have spin parity $11/2^{-}$. Consequently, the ground state has spin parity $5/2^{+}$. Excited levels in ${}^{147}\mathrm{La}$ have been arranged into a parity-doublet structure, showing that at medium excitation energy the ${}^{147}\mathrm{La}$ nucleus may have octupole deformation. The $B\left(E1\right)$ rates in ${}^{147}\mathrm{La}$, which are factor of four lower than in ${}^{145}\mathrm{La}$, suggest that the electric dipole moment in ${}^{147}\mathrm{La}$ is depressed by an extra mechanism, probably connected with the population of particular neutron orbitals.

Calculations in the $\mathit{sd}$ and $\mathit{pf}$ shells reported some time ago by Satuła et al. [Phys. Lett. B 407, 103 (1997)] are redone for an extended analysis of the results. As in the original work, we do calculations for one mass number in each shell and consider in each case the sequence of lowest energies for isospins 0, 2, and 4, briefly the symmetry spectrum. Following further the original work, we study how this spectrum changes when parts of the two-nucleon interaction are turned off. The variation of its width is explored in detail. A differential combination ${\epsilon }_{\text{W}}$ of the three energies was taken in the original work as a measure of the so-called Wigner term in semiempirical mass formulas, and it was found to decrease drastically when the two-nucleon interaction in the channel of zero isospin is turned off. Our analysis shows that the width of the symmetry spectrum experiences an equally drastic decrease, which can be explained qualitatively in terms of schematic approximations. We therefore suggest that the decrease of ${\epsilon }_{\text{W}}$ be seen mainly as a side effect of a narrowing of the symmetry spectrum rather than an independent manifestation of the two-nucleon interaction in the channel of zero isospin.

The relativistic-Hartree-Bogoliubov formalism using density-dependent zero and finite range $\mathit{NN}$ interactions, and separable pairing, is applied to the Kr isotopes ($Z=36$) and $N=34–64$ isotopes, neutron-rich Sr($Z=38$) and Zr($Z=40$) nuclei with neutron numbers $N=48–70$. A systematic search of triaxial ground state and the phenomena of unusual structural change and the coexistence of shape for ${}^{70-100}\mathrm{Kr}$, and at $N=58$ in the ${}^{86-108}\mathrm{Sr}$ and ${}^{88-110}\mathrm{Zr}$ isotopes are done. A reasonable agreement is found with the available experimental data and with the macro-microscopic finite range droplet model. The findings are also in good agreement with the self-consistent Hartree-Fock-Bogoliubov calculations based on the interaction Gogny-D1S force, and with relativistic calculations.

Projection of many-body states with good angular momentum from an initial state is usually accomplished by a three-dimensional integral. We show how projection can instead be done by solving a straightforward system of linear equations. We demonstrate the method and give sample applications to ${}^{48}\mathrm{Cr}$ and ${}^{60}\mathrm{Fe}$ in the $pf$ shell. This new projection scheme, which is competitive against the standard numerical quadrature, should also be applicable to other quantum numbers such as isospin and particle number.

The radiative capture cross section of a highly pure (99.999%), 6.125(2) grams and 9.56(5)$\times {10}^{-4}$ atoms/barn areal density ${}^{238}\mathrm{U}$ sample has been measured with the Total Absorption Calorimeter (TAC) in the 185 m flight path at the CERN neutron time-of-flight facility n_TOF. This measurement is in response to the NEA High Priority Request list, which demands an accuracy in this cross section of less than 3% below 25 keV. These data have undergone careful background subtraction, with special care being given to the background originating from neutrons scattered by the ${}^{238}\mathrm{U}$ sample. Pileup and dead-time effects have been corrected for. The measured cross section covers an energy range between 0.2 eV and 80 keV, with an accuracy that varies with neutron energy, being better than 4% below 25 keV and reaching at most 6% at higher energies.