We study the equation of state of neutron matter at finite temperature based on two- and three-nucleon interactions derived within chiral effective field theory to next-to-next-to-next-to-leading order. The free energy, pressure, entropy, and internal energy are calculated using many-body perturbation theory including terms up to third order around the self-consistent Hartree-Fock solution. We include contributions from three-nucleon interactions without employing the normal-ordering approximation and provide theoretical uncertainty estimates based on an order-by-order analysis in the chiral expansion. Our results demonstrate that thermal effects can be captured remarkably well via a thermal index and a density-dependent effective mass. The presented framework provides the basis for studying the dense matter equation of state at general temperatures and proton fractions relevant for core-collapse supernovae and neutron star mergers.

In the so-called pasta phases predicted to occur in neutron-star crusts, protons are able to move easily over large distances because the nuclear matter regions are extended in space. Consequently, electrical currents can be carried by protons, an effect not possible in conventional crystalline matter with isolated nuclei. With emphasis on the so-called lasagna phase, which has sheet-like nuclei, we describe the magnetic properties of the pasta phases allowing for proton superconductivity. We predict that these phases will be Type-II superconductors and we calculate the energy per unit length of a flux line, which is shown to be strongly anisotropic. If, as seems likely, the pasta structure is imperfect, flux lines will be pinned and matter will behave as a good electrical conductor and flux decay times will be long. We describe some possible astrophysical manifestations of our results.

The isotope shifts of the $3d^{9}4s{}^{3}D_3\to 3d^{9}4p{}^{3}P_2$ transition in the stable even-even nickel isotopes were measured. An improved accuracy was achieved by transforming the systematic contribution of the wavelength-meter-based laser-frequency measurement into a statistical-acting contribution by measuring the same observables at different frequency sets. A detailed King-fit analysis was performed to extract the mass-shift and field-shift parameters, which are crucial for the determination of the charge radii of short-lived isotopes from recently measured isotope shifts. A critical dependence of the achievable charge-radius accuracy on the choice of the reference isotope in the King-fit analysis was observed and is discussed.

Medium induced parton energy loss is not conclusively established either in very peripheral heavy-ion collisions or in proton-ion collisions. However, the standard interpretation of azimuthal momentum anisotropies in these systems implies some partonic rescattering. The upcoming light-ion runs at the Large Hadron Collider (LHC) provide a unique opportunity to search for parton energy loss in different systems of similar size. Here, we make predictions for the expected parton energy loss signal in the charged hadron spectra in a system size scan at LHC. We test a large set of model assumptions against the transverse momentum and centrality dependence of the charged hadron nuclear modification factor in lead-lead and xenon-xenon collisions at the LHC. We then attempt to make a model agnostic prediction for the charged hadron nuclear modification factor in oxygen-oxygen collisions.

Within the large-scale shell-model framework, an investigation of even-even nuclei in the vicinity of the ${}^{208}\mathrm{Pb}$ closed core is reported in the present work. The calculations of the low-lying state energies and the electromagnetic transitions of the Pb, Po, Rn, Ra, and Th nuclei with $126\le N\le 134$ are performed using a new effective interaction H208 derived from CD-Bonn nucleon-nucleon potential, through the $V_{\mathrm{low}\text{−}k}$ procedure. A special focus is devoted to the degree of the collectivity, where a transitional region from spherical nuclear shape to weakly collective behavior is revealed.

Chiral effective field theory $\left(\chi \mathrm{EFT}\right)$, as originally proposed by Weinberg, promises a theoretical connection between low-energy nuclear interactions and quantum chromodynamics (QCD). However, the important property of renormalization-group (RG) invariance is not fulfilled in current implementations and its consequences for predicting atomic nuclei beyond two- and three-nucleon systems has remained unknown. In this work we present a systematic study of recent RG-invariant formulations of $\chi \mathrm{EFT}$ and their predictions for the binding energies and other observables of selected nuclear systems with mass numbers up to $A=16$. Specifically, we have carried out ab initio no-core shell-model and coupled cluster calculations of the ground-state energy of ${}^3\mathrm{H}$, ${}^{3,4}\mathrm{He}$, ${}^6\mathrm{Li}$, and ${}^{16}\mathrm{O}$ using several recent power-counting (PC) schemes at leading order (LO) and next-to-leading order, where the subleading interactions are treated in perturbation theory. Our calculations indicate that RG-invariant and realistic predictions can be obtained for nuclei with mass number $A\le 4$. We find, however, that ${}^{16}\mathrm{O}$ is either unbound with respect to the four $\alpha$-particle threshold, or deformed, or both. Similarly, we find that the ${}^6\mathrm{Li}$ ground-state resides above the $\alpha$-deuteron separation threshold. These results are in stark contrast with experimental data and point to either necessary fine-tuning of all relevant counterterms, or that current state-of-the-art RG-invariant PC schemes at LO in $\chi \mathrm{EFT}$ lack necessary diagrams—such as three-nucleon forces—to realistically describe nuclei with mass number $A>4$.

Two-nucleon transfer reactions are essential tools to investigate specific features of the nuclear structure, such as the correlation among valence particles in the transfer process. Besides, transfer reactions may be an important channel to take into account in charge-exchange processes since they can represent a competing contribution to the final cross section. The two-proton pickup transfer reaction ${}^{40}\mathrm{Ca}({}^{18}\mathrm{O},{}^{20}\mathrm{Ne}){}^{38}\mathrm{Ar}$ has been measured at 270 MeV, and the angular distributions for transitions to different excited states extracted. This paper shows the analysis of the data performed by finite-range coupled reaction channel and coupled-channel Born approximation methods. Extensive shell-model calculations are performed to derive the one- and two-proton spectroscopic amplitudes for the projectile and target overlaps. The role of the simultaneous and sequential two-proton transfer mechanisms to populate the measured final states or groups of states, mainly characterized by a high collectivity, is also discussed.

Comprehensive calculations of photon-induced reactions on ${}^{233–238}\mathrm{U}$ targets for incident photon energies from 3 up to 30 MeV are undertaken with the statistical model code empire-3.2 Malta. Results are compared with the experimental data from EXFOR and with the current evaluations. The differences and the similarities between the models and parameters used in calculations of photon- and neutron-induced reactions on the same nuclei are discussed with focus on fission. The role of the extended optical model for fission that includes partial damping in the continuum in improving the description of the measured data is pointed out.

The incoherent approximation (IA) is often used for calculating the one-phonon inelastic neutron scattering cross section for arbitrary solids. It is valid for thermal neutrons but for slow neutrons it requires a correction, which is significant for isotopes that are strong coherent scatterers. In this article, we present the extension of the Placzek–Van Hove corrections for slow neutrons in the limit of low temperatures using the example of solid ortho-deuterium $\left({\mathrm{sD}}_2\right)$. Our approach yields realistic one-phonon up-scattering cross sections for ${\mathrm{sD}}_2$ and shows the IA to be a factor of 2–5 too high for ultracold neutron (UCN) up-scattering in ${\mathrm{sD}}_2$. Our calculations are compared with previously published Monte Carlo calculations of the one-phonon cross section based on the dynamic structure function $S(q,\omega )$ of polycrystalline ortho-deuterium and are found to be consistent with them. Furthermore, we provide the means for easily replicable calculations of the one-phonon up-scattering cross sections of solid ortho-deuterium for slow neutrons. These should from now on be used in calculations and simulations of UCN scattering in ${\mathrm{sD}}_2$.

Nonuniform structure of low-density nuclear matter, known as nuclear pasta, is expected to appear not only in the inner crust of neutron stars but also in core-collapse supernova explosions and neutron-star mergers. We perform fully three-dimensional calculations of inhomogeneous nuclear matter and neutron-star matter in the low-density region using the Thomas-Fermi approximation. The nuclear interaction is described in the relativistic mean-field approach with the point-coupling interaction, where the meson exchange in each channel is replaced by the contact interaction between nucleons. We investigate the influence of nuclear symmetry energy and its density dependence on pasta structures by introducing a coupling term between the isoscalar-vector and isovector-vector interactions. It is found that the properties of pasta phases in the neutron-rich matter are strongly dependent on the symmetry energy and its slope. In addition to typical shapes like droplets, rods, slabs, tubes, and bubbles, some intermediate pasta structures are also observed in cold stellar matter with a relatively large proton fraction. We find that nonspherical shapes are unlikely to be formed in neutron-star crusts, because the proton fraction obtained in $\beta$ equilibrium is somewhat small. The inner crust properties may lead to a visible difference in the neutron-star radius.

Background: The nucleosynthesis of neutron-deficient $p$ nuclei remains an unsolved puzzle in nuclear astrophysics. Most likely, huge networks containing hundreds of nuclear reactions are responsible for the creation of this group of nuclei. In reality, many of the relevant reaction rates cannot be studied experimentally but need to be estimated using global and robust theoretical approaches. The underlying nuclear physics that enters these calculations is often still not constrained well enough, especially for nuclei further off the valley of stability.

Purpose: Here, we complete the systematic measurement of radiative proton-capture reactions on stable Ag isotopes. The results will be used to test existing theoretical models and are crucial to constrain underlying nuclear physics properties. For this purpose, total cross sections of the ${}^{109}\mathrm{Ag}(p,\gamma ){}^{110}\mathrm{Cd}$ reaction have been measured at proton energies between 2.5 and 5.0 MeV.

Method: The cross-section measurements have been carried out by means of in-beam $\gamma$-ray spectroscopy and the observation of all ground-state transitions in ${}^{110}\mathrm{Cd}$. In general, the total cross sections depend strongly on the $\gamma$-ray strength function ($\gamma$-SF) and the nuclear level density (NLD). While the former one is taken from the systematics in other even-even Cd isotopes, the NLD has been constrained by renormalizing microscopic, tabulated values onto the low-lying cumulative number of levels.

Results: For the first time, ${}^{109}\mathrm{Ag}(p,\gamma ){}^{110}\mathrm{Cd}$ reaction cross sections have been reported over a wide range of beam energies. The total cross-section results are in good agreement with a rather limited, formerly published dataset. A convincing agreement with recent Hauser-Feshbach calculations is received when using existing descriptions for the $\gamma$-SF and a renormalized, microscopic NLD model.

Conclusion: The measured cross sections confirmed the reliability of existing theoretical models used in Hauser-Feshbach statistical model calculations. Coherent results are obtained for the statistical nuclear physics properties in the even-even Cd isotopes as well as for the derived experimental cross sections.

The critical properties for the transition to warm, asymmetric, nonhomogeneous nuclear matter are analyzed within a thermodynamical spinodal approach for a set of well-calibrated equations of state. It is shown that even though different equations of state are constrained by the same experimental, theoretical, and observational data, and the properties of symmetric nuclear matter are similar within the models, the properties of very asymmetric nuclear matter, such as the one found inside of neutron stars, differ a lot for various models. Some models predict larger transition densities to homogeneous matter for $\beta$-equilibrated matter than for symmetric nuclear matter. Since one expects that such properties have a noticeable impact on the the evolution of either a supernova or neutron star merger, this different behavior should be understood in more detail.

From the subleading contributions to the chiral three-nucleon (3N) interaction [published in Phys. Rev. C 77, 064004 (2008) and Phys. Rev. C 84, 054001 (2011)], their first-order contributions to the energy per particle of isospin-symmetric nuclear matter and pure neutron matter are derived in an analytical way. For the variety of short-range and long-range terms that constitute the subleading chiral 3N force the pertinent closed 3-ring, 2-ring, and 1-ring diagrams are evaluated. While 3-ring diagrams vanish by a spin-trace and the results for 2-ring diagrams can be given in terms of elementary functions of the ratio Fermi momentum over pion mass, one ends up in most cases for the closed 1-ring diagrams with one-parameter integrals. The same treatment is applied to the subsubleading chiral three-nucleon interactions as far as these have been constructed up to now.

The $E2/M1$ multipole mixing ratio of the $1_{\text{sc}}^{+}\to 2_1^{+}\gamma$-ray transition and therefore the $F$-vector $E2$ decay of the scissors mode of the shape-phase transitional nucleus ${}^{152}\mathrm{Sm}$ have been measured with the nuclear resonance fluorescence method at the High-Intensity $\gamma$-ray Source ($\mathrm{HI}\gamma \mathrm{S}$). Furthermore, parity quantum numbers of several dipole-excited states have been remeasured, making use of the polarized $\gamma$-ray beam at $\mathrm{HI}\gamma \mathrm{S}$, and partially reassigned. The new data enable an unambiguous determination of the proton and neutron effective boson quadrupole charges within the proton-neutron interacting boson model. With the well-constrained parameter set, a new mixed-symmetry state is predicted.

Nuclear reaction sensitivity studies have shown that the final isotopic abundance of O-Ne nova nucleosynthesis is dependent on the ${}^{34}\mathrm{S}(p,\gamma ){}^{35}\mathrm{Cl}$ reaction at astrophysical energies corresponding to peak nova burning temperatures of 0.1–0.4 GK. Isotopic ratios of the S, Cl, and Ar products are all used in various methods of cosmochemical analysis of presolar meteoritic grains. Due to the lack of direct experimental data, the ${}^{34}\mathrm{S}+p$ reaction rate has been estimated using statistical modeling or information from indirect nucleon transfer experiments. In order to provide direct reaction information, the resonance strengths of several low energy resonances, $E_{\mathrm{c}.\mathrm{m}.}=272–495$ keV, in the ${}^{34}\mathrm{S}(p,\gamma ){}^{35}\mathrm{Cl}$ reaction were measured for the first time in inverse kinematics using the DRAGON recoil separator located at TRIUMF, Canada's Particle Accelerator Centre in Vancouver.

In view of the planning experiments for collisions of light nuclei at relativistic heavy ion collider, the flow coefficients for O-O, Al-Al, and Cu-Cu collisions are studied in the color string percolation model. Our results for $v_2$ are somewhat smaller than predicted by other groups, although with the same dependence on centrality. Our obtained $v_3$ lie between predictions of other groups.

The first measurements of the scattering parameters of $\mathrm{\Lambda }K$ pairs in all three charge combinations ($\mathrm{\Lambda }{K}^{+}, \mathrm{\Lambda }{K}^{-}$, and $\mathrm{\Lambda }{K}_S^0$) are presented. The results are achieved through a femtoscopic analysis of $\mathrm{\Lambda }K$ correlations in Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV recorded by ALICE at the Large Hadron Collider. The femtoscopic correlations result from strong final-state interactions and are fit with a parametrization allowing for both the characterization of the pair emission source and the measurement of the scattering parameters for the particle pairs. Extensive studies with the THERMINATOR 2 event generator provide a good description of the nonfemtoscopic background, which results mainly from collective effects, with unprecedented precision. Furthermore, together with HIJING simulations, this model is used to account for contributions from residual correlations induced by feed-down from particle decays. The extracted scattering parameters indicate that the strong force is repulsive in the $\mathrm{\Lambda }{K}^{+}$ interaction and attractive in the $\mathrm{\Lambda }{K}^{-}$ interaction. The data hint that the $\mathrm{\Lambda }{K}_S^0$ interaction is attractive; however, the uncertainty of the result does not permit such a decisive conclusion. The results suggest an effect arising either from different quark-antiquark interactions between the pairs ($s\overline{s}$ in $\mathrm{\Lambda }{K}^{+}$ and $u\overline{u}$ in $\mathrm{\Lambda }{K}^{-}$) or from different net strangeness for each system ($S=0$ for $\mathrm{\Lambda }{K}^{+}$, and $S=-2$ for $\mathrm{\Lambda }{K}^{-}$). Finally, the $\mathrm{\Lambda }K$ systems exhibit source radii larger than expected from extrapolation from identical particle femtoscopic studies. This effect is interpreted as resulting from the separation in space-time of the single-particle $\mathrm{\Lambda }$ and $K$ source distributions.

We calculate two transport coefficients—the shear viscosity over entropy ratio $\eta /s$ and the ratio of the electric conductivity to the temperature, ${\sigma }_0/T$—of strongly interacting quark matter within the extended $N_f=3$ Polyakov Nambu-Jona-Lasinio (PNJL) model along the crossover transition line for moderate values of baryon chemical potential $0\le {\mu }_B\le 0.9\mathrm{GeV}$ as well as in the vicinity of the critical endpoint (CEP) and at large baryon chemical potential ${\mu }_B=1.2\mathrm{GeV}$, where the first-order phase transition takes place. The evaluation of the transport coefficients is performed on the basis of the effective Boltzmann equation in the relaxation time approximation. We employ two different methods for the calculation of the quark relaxation times: (i) using the averaged transition rate defined via thermal averaged quark-quark and quark-antiquark PNJL cross sections and (ii) using the “weighted” thermal averaged quark-quark and quark-antiquark PNJL cross sections. The $\eta /s$ and ${\sigma }_0/T$ transport coefficients have similar temperature and chemical potential behaviors when approaching the chiral phase transition for both methods for the quark relaxation time; however, the differences grow with increasing temperature. We demonstrate the effect of the first-order phase transition and of the CEP on the transport coefficients in the deconfined QCD medium.

Octupole deformations and related collective excitations are analyzed using the framework of nuclear density functional theory. Axially symmetric quadrupole-octupole constrained self-consistent mean-field (SCMF) calculations with a choice of universal energy density functional and a pairing interaction are performed for Xe, Ba, and Ce isotopes from proton-rich to neutron-rich regions, and neutron-rich Se, Kr, and Sr isotopes, in which enhanced octupole correlations are expected to occur. Low-energy positive- and negative-parity spectra and transition strengths are computed by solving the quadrupole-octupole collective Hamiltonian, with the inertia parameters and collective potential determined by the constrained SCMF calculations. Octupole-deformed equilibrium states are found in the potential energy surfaces of the Ba and Ce isotopes with $N\approx 56$ and 88. The evolution of spectroscopic properties indicates enhanced octupole correlations in the regions corresponding to $N\approx Z\approx 56$, $Z\approx 88$ and $Z\approx 56$, and $N\approx 56$ and $Z\approx 34$. The average ${\beta }_{30}$ deformation parameter and its fluctuation exhibit signatures of octupole shape-phase transition around $N=56$ and 88.