The emergence of rotational bands is observed in no-core configuration interaction (NCCI) calculations for the $\mathrm{Be}$ isotopes ($7\le A\le 12$), as evidenced by rotational patterns for excitation energies, electromagnetic moments, and electromagnetic transitions. Yrast and low-lying excited bands are found. The results indicate well-developed rotational structure in NCCI calculations, using the JISP16 realistic nucleon-nucleon interaction within finite, computationally accessible configuration spaces.

Background: Shell-model calculations crucially depend on the residual interaction used to approximate the nucleon-nucleon interaction. Recent improvements to the empirical universal $sd$ interaction (USD) describing nuclei within the $sd$ shell yielded two new interactions—USDA and USDB—causing changes in the theoretical description of these nuclei.

Purpose: Transition matrix elements between excited states provide an excellent probe to examine the underlying shell structure. These observables provide a stringent test for the newly derived interactions. The nucleus ${}^{26}\mathrm{Na}$ with 7 valence neutrons and 3 valence protons outside the doubly-magic ${}^{16}\mathrm{O}$ core is used as a test case.

Method: A radioactive beam experiment with ${}^{26}\mathrm{Na}$ ($T_{1/2}=1,07s$) was performed at the REX-ISOLDE facility (CERN) using Coulomb excitation at safe energies below the Coulomb barrier. Scattered particles were detected with an annular Si detector in coincidence with $\gamma$ rays observed by the segmented MINIBALL array. Coulomb excitation cross sections of the beam have been obtained by normalization to the well known Coulomb excitation cross sections of the ${}^{104}\mathrm{Pd}$ target.

Results: The observation of three $\gamma$-ray transitions in ${}^{26}\mathrm{Na}$ together with available spectroscopic data allows us to determine $E2$- and $M1$-transitional matrix elements. Results are compared to theoretical predictions.

Conclusion: The improved theoretical description of ${}^{26}\mathrm{Na}$ could be validated. Remaining discrepancies between experimental data and theoretical predictions indicate the need for future experiments and possibly further theoretical improvements.

A set of evolution equations for correlators of densities of quarks and gluons is considered. Approximate solutions are derived in the framework of the gluon and quark dominance. A new approach to estimate the cross sections of the processes with the interaction of high energy hadrons within the parton model is proposed. This approach is demonstrated in a set of processes of hadron-hadron collisions with QCD subprocesses of $2\to 2$ type. The process with the subprocess $gb\to t{H}^{-}$ was also considered.

We study the impact of the symmetry energy on properties of nuclear pasta phases and crust-core transition in neutron stars. We perform a self-consistent Thomas-Fermi calculation employing the relativistic mean-field model. The properties of pasta phases presented in the inner crust of neutron stars are investigated and the crust-core transition is examined. It is found that the slope of the symmetry energy plays an important role in determining the pasta phase structure and the crust-core transition. The correlation between the symmetry energy slope and the crust-core transition density obtained in the Thomas-Fermi approximation is consistent with that predicted by the liquid-drop model.

Calculations of elastic scattering angular distributions for reactions of the weakly bound projectile ${}^6\mathrm{Li}$ with targets ${}^{28}\mathrm{Si}$ and ${}^{58}\mathrm{Ni}$ at energies just above the Coulomb barrier are performed with the continuum-discretized coupled-channel calculation method. Ground, resonant, and nonresonant continuum states of ${}^6\mathrm{Li}$ are included in the convergent calculations. The effect of the resonances on elastic scattering angular distributions is studied, in an original procedure, by excluding from the continuum space those states corresponding to the resonances. When the resonances of ${}^6\mathrm{Li}$ are considered, the calculated elastic scattering angular distributions are in good agreement with the measurements. The exclusion of the resonances, unexpectedly, has a very small effect at the energies studied. Calculation of the polarization potentials associated with the resonances show that they have a repulsive character at the long range region, where scattering occurs. It is also confirmed that couplings to continuum states of ${}^6\mathrm{Li}$ are essential to achieve agreement with the data.

We report the results of the measurements of complete and incomplete fusion of the ${}^9\text{Be}+{}^{169}\text{Tm}$ and ${}^{187}\mathrm{Re}$ systems at energies close to the Coulomb barrier. The activation technique with the detection of offline gamma rays was used to derive the cross sections. By comparing the experimental cross sections with coupled-channel calculations that do not include the breakup channel, we found suppression of the complete fusion of the order of 30% for both systems, at energies slightly above the barrier. This suppression corresponds roughly to the measured incomplete fusion. We also investigate a systematic behavior of the suppression of complete fusion cross sections for ${}^9\mathrm{Be}$ on different targets and we found that it does not depend on the target.

Neutron evaporation spectra along with $\gamma$ multiplicity has been measured from ${}^{201}\mathrm{Tl}{}^{*},{}^{185}\mathrm{Re}{}^{*}$, and ${}^{169}\mathrm{Tm}{}^{*}$ compound nuclei at the excitation energies of $\sim 27$ and 37 MeV. Statistical model analysis of the experimental data has been carried out to extract the value of the inverse level density parameter $k$ at different angular-momentum $\left(J\right)$ regions corresponding to different $\gamma$ multiplicities. It is observed that, for the present systems the value of $k$ remains almost constant for different $J$. The present results for the angular-momentum dependence of the nuclear level density (NLD) parameter $\tilde{a}(=A/k)$, for nuclei with $A\sim 180$ are quite different from those obtained in earlier measurements in the case of light- and medium-mass systems. The present study provides useful information to understand the angular-momentum dependence of the NLD at different nuclear mass regions.

The synchrotron photon spectrum in heavy ion collisions is computed taking into account the spatial and temporal structure of the magnetic field. It is found that a significant fraction of photon excess in heavy ion collisions in the region $k_{\perp }=1\text{–}3$ GeV can be attributed to the synchrotron radiation. Azimuthal anisotropy of the synchrotron photon spectrum is characterized by the Fourier coefficients $v_2=4/7$ and $v_4=1/10$ that are independent of photon momentum and centrality.

Neutrons stars lighter than the Sun are basically composed of nuclear matter of density up to around twice normal nuclear density. In our recent analyses, we showed that possible simultaneous observations of masses and radii of such neutron stars could constrain $\eta \equiv {\left(K_0{L}^2\right)}^{1/3}$, a combination of the incompressibility of symmetric nuclear matter $K_0$ and the density derivative of the nuclear symmetry energy $L$ that characterizes the theoretical mass-radius relation. In this paper, we focus on the mass-radius constraint of the x-ray burster 4U 1724-307 given by Suleimanov et al. [V. Suleimanov, J. Poutanen, M. Revnivtsev, and K. Werner, Astrophys. J. 742, 122 (2011)]. We therefrom obtain the constraint that $\eta$ should be larger than around 130 MeV, which in turn leads to $L$ larger than around 110, 98, 89, and 78 MeV for $K_0=180$, 230, 280, and 360 MeV. Such a constraint on $L$ is more or less consistent with that obtained from the frequencies of quasi-periodic oscillations in giant flares observed in soft gamma repeaters.

The observed rapid cooling of the Cassiopeia A neutron star can be interpreted as being caused by neutron and proton transitions from normal to superfluid and superconducting states in the stellar core. Here we present two new Chandra ACIS-S Graded observations of this neutron star and measurements of the neutron star mass $M$ and radius $R$ found from consistent fitting of both the x-ray spectra and cooling behavior. This comparison is only possible for individual nuclear equations of state. We test phenomenological superfluid and superconducting gap models which mimic many of the known theoretical models against the cooling behavior. Our best-fit solution to the Cassiopeia A data is one in which the $(M,R)=(1.44M_{\mathrm{Sun}},12.6\text{km})$ neutron star is built with the BSk21 equation of state, strong proton superconductor and moderate neutron triplet superfluid gap models, and a pure iron envelope or a thin carbon layer on top of an iron envelope, although there are still large observational and theoretical uncertainties.

The TETFSI (temperature-dependent extended Thomas-Fermi plus Strutinsky integral) method for calculating the properties of the inner crust of neutron stars is here extended in the zero-temperature limit to include proton pairing. The main effect is to smooth out the proton shell effects, although the energetically favored value of $Z$, the number of protons per Wigner-Seitz cell, remains at, or close to, 40.

Our current knowledge of the baryon-baryon interaction suggests that the dineutron $(n,n)$ and its strange analog $(n,\Lambda )$ are unstable. In contrast, the situation is more favorable for the strange three-body system $(n,n,\Lambda )$, and even better for the four-body system $T\equiv (n,n,\Lambda ,\Lambda )$ with strangeness $-2$, which is likely to be stable under spontaneous dissociation. The recent models of the hyperon-nucleon and hyperon-hyperon interactions suggest that the stability of the $(n,n,\Lambda )$ and $T$ is possible within the uncertainties of our knowledge of the baryon-baryon interactions. This new nucleus $T$ could be produced and identified in central deuteron-deuteron collisions viathe reaction $d+d\to T+K^{+}+K^{+}$, and the tetrabaryon $T$ could play an important role in catalyzing the formation of a strange core in neutron stars.

We develop a method for calculating the bound and continuum energy spectrum of three particles interacting through both short-range and Coulomb potentials. Our method combines hyperspherical coordinates with the slow variable discretization approach. A complex absorbing potential is employed to describe accurately the continuum wave functions. The method is well known in atomic and molecular physics. It is extended here to nuclear physics, with a special emphasis on the long-range Coulomb interaction. The method is applied to compute the energy spectrum of ${}^{12}\mathrm{C}$ in a $3\alpha$-particle model, focusing on an accurate calculation of the Hoyle resonance width of the narrow near-threshold $J_n^{\pi }=0_2^{+}$ state, which plays an important role in stellar nucleosynthesis. We employ an effective $\alpha \text{−}\alpha$ interaction potential which reproduces both the energy and width of ${}^8\mathrm{Be}$, while a three-body force is added in order to fix the ${}^{12}\mathrm{C}$ energy levels at the experimental values. We also analyze the structure of the bound and resonance states by calculating the wave functions and one-dimensional distribution functions.

The quadrupole vibrational modes of neutron-rich $N=28$ isotones (${}^{48}\mathrm{Ca}$, ${}^{46}\mathrm{Ar}$, ${}^{44}\mathrm{S}$, and ${}^{42}\mathrm{Si}$) are investigated by using the canonical-basis time-dependent Hartree–Fock–Bogoliubov theory with several choice of energy density functionals, including nuclear pairing correlation. It is found that the quenching of the $N=28$ shell gap and the proton holes in the $sd$ shell trigger quadrupole correlation and increase the collectivity of the low-lying $2^{+}$ state in ${}^{46}\mathrm{Ar}$. It is also found that the pairing correlation plays an important role to increase the collectivity. We also demonstrate that the same mechanism to enhance the low-lying collectivity applies to other $N=28$ isotones ${}^{44}\mathrm{S}$ and ${}^{42}\mathrm{Si}$, and it generates a couple of low-lying $2^{+}$ states which can be associated with the observed $2^{+}$ states.

We study the effects of density-dependent weak vector form factors on the inclusive neutral-current–neutrino (antineutrino)-nucleus scattering in the quasi-elastic region within the framework of a relativistic single-particle model. The density-dependent weak form factors are obtained from a quark-meson coupling model. The density-dependence effects are studied separately in protons and neutrons participating in the reactions, in each response cross section, and with regard to asymmetry. These density effects reduce the cross section at high densities and show different behavior with regard to asymmetry. Furthermore we calculate flux-averaged differential cross sections and compare them with the experimental data.

Background: The thermonuclear ${}^{34g,m}\mathrm{Cl}{(p,\gamma )}^{35}\mathrm{Ar}$ reaction rates are unknown due to a lack of experimental nuclear physics data. Uncertainties in these rates translate to uncertainties in ${}^{34}\mathrm{S}$ production in models of classical novae on oxygen-neon white dwarfs. ${}^{34}\mathrm{S}$ abundances have the potential to aid in the classification of presolar grains.

Purpose: Determine resonance energies for the ${}^{34g,m}\mathrm{Cl}{(p,\gamma )}^{35}\mathrm{Ar}$ reactions within the region of astrophysical interest for classical novae to a precision of a few keV as an essential first step toward constraining their thermonuclear reaction rates.

Method: ${}^{35}\mathrm{Ar}$ excited states were populated by the ${}^{36}\mathrm{Ar}{(d,t)}^{35}\mathrm{Ar}$ reaction at $E\left(d\right)=22\mathrm{MeV}$ and reaction products were momentum analyzed by a high resolution quadrupole-dipole-dipole-dipole (Q3D) magnetic spectrograph.

Results: Seventeen new ${}^{35}\mathrm{Ar}$ levels have been detected at a statistically significant level in the region $E_x\approx 5.9–6.7\mathrm{MeV}$ $(E_r<800\mathrm{keV})$ and their excitation energies have been determined to typical uncertainties of 3 keV. The uncertainties for five previously known levels have also been reduced substantially. The measured level density was compared to those calculated using the WBMB Hamiltonian within the $sd\text{−}pf$ model space.

Conclusions: Most of the resonances in the region of astrophysical interest have likely been discovered and their energies have been determined, but the resonance strengths are still unknown, and experimentally constraining the ${}^{34g,m}\mathrm{Cl}{(p,\gamma )}^{35}\mathrm{Ar}$ reaction rates will require further experiments.

We perform a systematic assessment of models for the equation of state (EOS) of dense matter in the context of recent neutron star mass and radius measurements to obtain a broad picture of the structure of neutron stars. We demonstrate that currently available neutron star mass and radius measurements provide strong constraints on moments of inertia, tidal deformabilities, and crust thicknesses. A measurement of the moment of inertia of PSR J0737-3039A with a 10% error, without any other information from observations, will constrain the EOS over a range of densities to within 50%–60%. We find tidal deformabilities between 0.6 and $6\times {10}^{36}\mathrm{g}{\mathrm{cm}}^2{\mathrm{s}}^2$ (to 95% confidence) for $M=1.4M_{\odot }$, and any measurement which constrains this range will provide an important constraint on dense matter. The crustal fraction of the moment of inertia can be as large as 10% for $M=1.4M_{\odot }$ permitting crusts to have a large enough moment of inertia reservoir to explain glitches in the Vela pulsar even with a large amount of superfluid entrainment. Finally, due to the uncertainty in the equation of state, there is at least a 40% variation in the thickness of the crust for a fixed mass and radius, which implies that future simulations of the cooling of a neutron star crust which has been heated by accretion will need to take this variation into account.

The superheavy nuclear production mechanism can be described by fusion reactions with the dinuclear system concept, in which the deformations of the two nuclei are assumed to stay at their ground state with nucleons transferring between them. Actually the two nuclei have to deform due to very strong nuclear and Coulomb interactions between them. These deformations can be analytically described by a Fokker-Planck equation, and by combining them with a master equation that describes the nucleon transfer between nuclei the superheavy nuclear production cross sections can be investigated systematically. The calculated results are in good agreement with available data, and the evaporation residue cross sections for synthesizing the superheavy nuclei $Z=119$ and 120 are predicted.

A model combining self-consistent mean-field and shell-model techniques is used to study the competition between particle-like and proton-neutron pairing correlations in $fp$-shell even-even self-conjugate nuclei. Results obtained using constant two-body pairing interactions as well as more sophisticated interactions are presented and discussed. The standard BCS calculations are systematically compared with more refined approaches including correlation effects beyond the independent quasiparticle approach. The competition between proton-neutron correlations in the isoscalar and isovector channels is also analyzed, as well as their dependence on the deformation properties. Besides the expected role of the spin-orbit interaction and particle number conservation, it is shown that deformation leads to a reduction of the pairing correlations. This reduction originates from the change of the single-particle spectrum and from a quenching of the residual pairing matrix elements. The competition between isoscalar and isovector pairing in the deuteron transfer is finally addressed. Although a strong dependence the isovector pairing correlations with respect to nuclear deformation is observed, they always dominate over the isoscalar ones.

Early growth of density fluctuations of nuclear matter in the spinodal region is investigated employing the stochastic mean-field approach. In contrast to the earlier treatments in which only collective modes were included in the calculations, in the present work noncollective modes are also included, thus providing a complete treatment of the density correlation functions. Calculations are carried out for symmetric matter in a nonrelativistic framework using a semiclassical approximation.