The equation of state of baryon-symmetric hadronic matter with hard-sphere interactions is studied. It is assumed that mesons $M$ are pointlike, but baryons $B$ and antibaryons $\overline{B}$ have the same hard-core radius $r_B$. Three possibilities are considered: (1) the $BB$ and $B\overline{B}$ interactions are the same; (2) baryons do not interact with antibaryons; (3) the $B\overline{B}, MB$, and $M\overline{B}$ interactions are negligible. By choosing the parameter $r_B=0.3–0.6$ fm, we calculate the nucleon to pion ratio as a function of temperature and perform the fit of hadron yields measured in central Pb+Pb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$. New nontrivial effects in the interacting hadron resonance gas at temperatures $150–200$ MeV are found.

Background: The emergence of hyperon degrees of freedom in neutron star matter has been associated to first-order phase transitions in some phenomenological models, but conclusions on the possible physical existence of an instability in the strangeness sector are strongly model dependent.

Purpose: The purposes of the present study are to assess whether strangeness instabilities are related to specific values of the largely unconstrained hyperon interactions and to study the effect of the strange meson couplings on phenomenological properties of neutron stars and supernova matter, once these latter are fixed to fulfill the constraints imposed by hypernuclear data.

Method: We consider a phenomenological relativistic mean field model (RMF) model sufficiently simple to allow a complete exploration of the parameter space.

Results: We show that no instability at supersaturation density exists for the RMF model, as long as the parameter space is constrained by basic physical requirements. This is at variance with a nonrelativistic functional, with a functional behavior fitted through ab initio calculations. Once the study is extended to include the full octet, we show that the parameter space allows reasonable radii for canonical neutron stars as well as massive stars above two-solar mass, together with an important strangeness content of the order of 30%, slightly decreasing with increasing entropy, even in the absence of a strangeness-driven phase transition.

Conclusions: We conclude that the hyperon content of neutron stars and supernova matter cannot be established with present constraints, and is essentially governed by the unconstrained coupling to the strange isoscalar meson.

The pairing anti-halo effect is a phenomenon that a pairing correlation suppresses a divergence of nuclear radius, which happens for single-particle states with orbital angular momenta of $l=0$ and 1 in the limit of vanishing binding energy. While this effect has mainly been discussed in terms of Hartree-Fock-Bogoliubov (HFB) theory, we here use a three-body model and provide its new intuitive concept as a localized wave packet for a quasiparticle, that is, a coherent superposition of a weakly bound and continuum wave functions due to a pairing interaction. We show that the one-particle density in the three-body model can be directly expressed with such quasiparticle wave functions, which have a close analog to wave functions in the HFB approximation.

The properties of neutron stars are investigated within the relativistic central variational method by using a realistic nucleon-nucleon ($NN$) interaction. The strong repulsion of realistic $NN$ interactions at short distances is treated by a Jastrow central correlation function, whose form is completely determined through minimization of the total energy of the nuclear many-body system. The relativistic Hartree-Fock wave functions are chosen as the trial wave function. In this framework, the equation of state of the neutron star matter in $\beta$ equilibrium is obtained self-consistently. We further determine the properties of neutron stars via the Tolman-Oppenheimer-Volkoff equation using Bonn A, B, and C potentials. The maximum masses of neutron stars with these realistic potentials are around $2.18M_{\odot }$ and their corresponding radii are around 11 km. These results are in accordance with the calculations of the relativistic Brueckner-Hartree-Fock theory with the same potentials. Furthermore, we also find that the splitting of proton-neutron effective masses will be reversed at high density in the neutron star matter, which are caused by the contribution of short-range correlation on kinetic energy.

We present solutions of the BCS gap equation in the channels ${}^{1}S_0$ and ${}^{3}P_2–{}^{3}F_2$ in neutron matter based on nuclear interactions derived within chiral effective field theory (EFT). Our studies are based on a representative set of nonlocal nucleon-nucleon (NN) plus three-nucleon (3N) interactions up to next-to-next-to-next-to-leading order (${\mathrm{N}}^3\mathrm{LO}$) as well as local and semilocal chiral NN interactions up to ${\mathrm{N}}^2\mathrm{LO}$ and ${\mathrm{N}}^4\mathrm{LO}$, respectively. In particular, we investigate for the first time the impact of subleading 3N forces at ${\mathrm{N}}^3\mathrm{LO}$ on pairing gaps and also derive uncertainty estimates by taking into account results for pairing gaps at different orders in the chiral expansion. Finally, we discuss different methods for obtaining self-consistent solutions of the gap equation. Besides the widely used quasilinear method by Khodel et al., we demonstrate that the modified Broyden method is well applicable and exhibits a robust convergence behavior. In contrast to Khodel's method it is based on a direct iteration of the gap equation without imposing an auxiliary potential and is straightforward to implement.

Quark-gluon plasmas produced in relativistic heavy-ion collisions quickly expand and cool, entering a phase consisting of multiple interacting hadronic resonances just below the QCD deconfinement temperature, $T\sim 155$ MeV. Numerical microscopic simulations have emerged as the principal method for modeling the behavior of the hadronic stage of heavy-ion collisions, but the transport properties that characterize these simulations are not well understood. Methods are presented here for extracting the shear viscosity and two transport parameters that emerge in Israel-Stewart hydrodynamics. The analysis is based on studying how the stress-energy tensor responds to velocity gradients. Results are consistent with Kubo relations if viscous relaxation times are twice the collision time.

A new measurement of the angular distribution of neutron elastic scattering on deuterium was carried out at the neutron time-of-flight facility nELBE. The backward-forward asymmetry of the reaction was investigated via the direct detection of neutrons scattered at the laboratory angle of ${15}^{\circ }$ and ${165}^{\circ }$ from a polyethylene sample enriched with deuterium. In order to extend the measurement to neutron energies below 1 MeV, ${}^6\mathrm{Li}$ glass scintillators were employed. The data were corrected for the background and the multiple scattering in the target, the events due to scattering on deuterium were separated from those due to carbon, and the ratio of the differential cross section at ${15}^{\circ }$ and ${165}^{\circ }$ was determined. The results, covering the energy range from 200 keV to 2 MeV, were found to be in agreement with the theoretical predictions calculated by Canton et al. [Eur. Phys. J. A 14, 225 (2002)] and by Golak et al. [Eur. Phys. J. A 50, 177 (2014)]. The comparison with the evaluated nuclear data libraries indicated CENDL-3.1, JEFF-3.2, and JENDL-4.0 as the evaluations that best describe the asymmetry of $n\text{−}d$ scattering. ENDF/B-VII.1 is compatible with the data for energies below 700 keV, but above the backward to forward ratio is higher than measured. ROSFOND-2010 and BROND-2.2 resulted to have little compatibility with the data.

The influence of single-neutron stripping on the near-barrier elastic scattering angular distributions for the ${}^{6,8}\mathrm{He}+{}^{208}\mathrm{Pb}$ systems is investigated through coupled reaction channels (CRC) calculations fitting recently published data to explore the differences in the absorptive potential found in the scattering of these two neutron-rich nuclei. The inclusion of the coupling reduces the elastic cross section in the Coulomb-nuclear interference region for ${}^8\mathrm{He}$ scattering, whereas for ${}^6\mathrm{He}$ its major impact is on the large-angle elastic scattering. The real and imaginary dynamic polarization potentials are obtained by inverting the CRC elastic scattering $S$-matrix elements. These show that the main absorptive features occur between 11 and 12 fm for both projectiles, while the attractive features are separated by about 1 fm, with their main structures occurring at 10.5 fm for ${}^6\mathrm{He}$ and 11.5 fm for ${}^8\mathrm{He}$.

Theoretical models of the $(d,p)$ reaction are exploited for both nuclear astrophysics and spectroscopic studies in nuclear physics. Usually, these reaction models use local optical model potentials to describe the nucleon- and deuteron-target interactions. Within such a framework, the importance of the deuteron $D$ state in low-energy reactions is normally associated with spin observables and tensor polarization effects, with very minimal influence on differential cross sections. In contrast, recent work that includes the inherent nonlocality of the nucleon optical model potentials in the Johnson-Tandy adiabatic-model description of the $(d,p)$ transition amplitude, which accounts for deuteron break-up effects, shows sensitivity of the reaction to the large $n-p$ relative momentum content of the deuteron wave function. The dominance of the deuteron $D$-state component at such high momenta leads to significant sensitivity of calculated $(d,p)$ cross sections and deduced spectroscopic factors to the choice of deuteron wave function [Phys. Rev. Lett. 117, 162502 (2016)]. We present details of the Johnson-Tandy adiabatic model of the $(d,p)$ transfer reaction generalized to include the deuteron $D$ state in the presence of nonlocal nucleon-target interactions. We present exact calculations in this model and compare these to approximate (leading-order) solutions. The latter, approximate solutions can be interpreted in terms of local optical potentials, but evaluated at a shifted value of the energy in the nucleon-target system. This energy shift is increased when including the $D$-state contribution. We also study the expected dependence of the $D$-state effects on the separation energy and orbital angular momentum of the transferred nucleon. Their influence on the spectroscopic information extracted from $(d,p)$ reactions is quantified for a particular case of astrophysical significance.

The cross section of the ${}^{23}\mathrm{Na}(n,\gamma ){}^{24}\mathrm{Na}$ reaction was measured via the activation method at the Karlsruhe 3.7 MV Van de Graaff accelerator. NaCl samples were exposed to quasistellar neutron spectra at $kT=5.1$ and 25 keV produced via the ${}^{18}\mathrm{O}(p,n){}^{18}\mathrm{F}$ and ${}^7\mathrm{Li}(p,n){}^7\mathrm{Be}$ reactions, respectively. The derived capture cross sections ${\langle \sigma \rangle }_{\mathrm{kT}=5\mathrm{keV}}=9.1\pm 0.3$ mb and ${\langle \sigma \rangle }_{\mathrm{kT}=25\mathrm{keV}}=2.03\pm 0.05$ mb are significantly lower than reported in literature. These results were used to substantially revise the radiative width of the first ${}^{23}\mathrm{Na}$ resonance and to establish an improved set of Maxwellian average cross sections. The implications of the lower capture cross section for current models of $s$-process nucleosynthesis are discussed.

Excited states have been observed for the first time in the neutron-deficient nucleus ${}^{117}\mathrm{Ba}$ using the recoil-decay tagging technique following the heavy-ion fusion-evaporation reaction ${}^{64}\mathrm{Zn}$(${}^{58}\mathrm{Ni}$, 2p3n)${}^{117}\mathrm{Ba}$. Prompt $\gamma$ rays have been assigned to ${}^{117}\mathrm{Ba}$ through correlations with $\beta$-delayed protons following the decay of $A=117$ recoils. Through the analysis of the $\gamma -\gamma$ coincidence relationships, a high-spin level scheme consisting of two bands has been established in ${}^{117}\mathrm{Ba}$. Based on the systematics of the level spacings in the neighboring barium isotopes, the two bands are proposed to have $\nu h_{11/2}\left[532\right]5/2^{-}$ and $\nu d_{5/2}\left[413\right]5/2^{+}$ configurations, respectively. The observed band-crossing properties are interpreted in the framework of cranked shell model.

We extend our virial approach to study the neutral-current neutrino response of nuclear matter at low densities. In the long-wavelength limit, the virial expansion makes model-independent predictions for neutrino-nucleon scattering rates and the density $S_V$ and spin $S_A$ responses. We find that $S_A$ is significantly reduced from one even at low densities. We provide a simple fit $S_A^f(n,T,Y_p)$ of the axial response as a function of density $n$, temperature $T$, and proton fraction $Y_p$, which can be incorporated into supernova simulations in a straightforward manner. This fit reproduces our virial results at low densities and the Burrows and Sawyer random-phase approximation (RPA) model calculations at high densities. Preliminary one-dimensional supernova simulations suggest that the virial reduction in the axial response may enhance neutrino heating rates in the gain region during the accretion phase of a core-collapse supernovae.

To systematically examine the possible maximum mass of neutron stars, which is one of the important properties characterizing the physics in high-density regions, I construct neutron star models by adopting phenomenological equations of state with various values of nuclear saturation parameters for low-density regions, which are connected to the equation of state for high-density regions characterized by the possible maximum sound velocity in medium. I derive an empirical formula for the possible maximum mass of neutron stars. If massive neutron stars are observed, it could be possible to get a constraint on the possible maximum sound velocity for high-density regions.

Cross sections of the radiative proton capture reaction ${}^9\mathrm{Be}(p,\gamma )$, leading to the low-lying excited states in ${}^{10}\mathrm{B}$ with isospin $T=0$ and 1, have been measured over the proton energy range of 7 to 20 MeV. For this, the method of coincidence between the primary and the secondary $\gamma$ rays has been used. These $\gamma$ rays are emitted following, respectively, the proton capture to an excited state and the subsequent decay of that state. A direct-semidirect capture model calculation has been performed and compared with the experimental data. The experimental results do not show a strong isospin dependence of the GDR strength function built on the low-lying states. The derived photoproton cross sections on these states and the earlier-measured photoneutron cross sections on the ground state of ${}^{10}\mathrm{B}$ show a large difference.

We present ${}^8\mathrm{B}+{}^{27}\mathrm{Al}$ elastic scattering angular distributions for the proton-halo nucleus ${}^8\mathrm{B}$ at two energies above the Coulomb barrier, namely $E_{\mathrm{lab}}=15.3$ and 21.7 MeV. The experiments were performed in the Radioactive Ion Beams in Brasil facility (RIBRAS) in São Paulo, and in the TwinSol facility at the University of Notre Dame, USA. The angular distributions were measured in the angular range of 15–80 degrees. Optical model and continuum discretized coupled channels calculations were performed, and the total reaction cross sections were derived. A comparison of the ${}^8\mathrm{B}+{}^{27}\mathrm{Al}$ total reaction cross sections with similar systems including exotic, weakly bound, and tightly bound projectiles impinging on the same target is presented.

In the nuclear mass range $A\approx 60$ to 90 of the solar abundance distribution the weak $s$-process component is the dominant contributor. In this scenario, which is related to massive stars, the overall neutron exposure is not sufficient for the $s$ process to reach mass flow equilibrium. Hence, abundances and isotopic ratios are very sensitive to the neutron capture cross sections of single isotopes, and nucleosynthesis models need accurate experimental data. In this work we report on a new measurement of the ${}^{63}\mathrm{Cu}(n,\gamma )$ cross section for which the existing experimental data show large discrepancies. The ${}^{63}\mathrm{Cu}(n,\gamma )$ cross section at $k_{B}T=25$ keV was determined via activation with a quasistellar neutron spectrum at the Joint Research Centre (JRC) in Geel, and the energy dependence was determined with the time-of-flight technique and the calorimetric $4\pi {\mathrm{BaF}}_2$ detector array DANCE at the Los Alamos National Laboratory. We provide new cross section data for the whole astrophysically relevant energy range.

Using a multireflection time-of-flight mass spectrograph located after a gas cell coupled with the gas-filled recoil ion separator GARIS-II, the masses of several $\alpha$-decaying heavy nuclei were directly and precisely measured. The nuclei were produced via fusion-evaporation reactions and separated from projectilelike and targetlike particles using GARIS-II before being stopped in a helium-filled gas cell. Time-of-flight spectra for three isobar chains, ${}^{204}\mathrm{Fr}-{}^{204}\mathrm{Rn}-{}^{204}\mathrm{At}-{}^{204}\mathrm{Po}, {}^{205}\mathrm{Fr}-{}^{205}\mathrm{Rn}-{}^{205}\mathrm{At}-{}^{205}\mathrm{Po}-{}^{205}\mathrm{Bi}$, and ${}^{206}\mathrm{Fr}-{}^{206}\mathrm{Rn}-{}^{206}\mathrm{At}$, were observed. Precision atomic mass values were determined for ${}^{204–206}\mathrm{Fr}, {}^{204,205}\mathrm{Rn}$, and ${}^{204,205}\mathrm{At}$. Identifications of ${}^{205}\mathrm{Bi}, {}^{204,205}\mathrm{Po}, {}^{206}\mathrm{Rn}$, and ${}^{206}\mathrm{At}$ were made with $N\lesssim 10$ detected ions, representing the next step toward use of mass spectrometry to identify exceedingly low-yield species such as superheavy element ions.