Strange particles and hyperfragments in collisions of antiprotons and protons on nuclei have been investigated systematically within a microscopic transport model. The hyperons are produced from the annihilation in antibaryon-baryon collisions and the strangeness exchange process in antiproton induced reactions. A coalescence approach is used to construct the primary hyperfragments in phase space and the statistical model is modified to describe the decay of hyperfragments via evaporating hyperon, neutron, charged particles, etc., in which the shell effect, binding energy, and root-mean-square radii are taken into account. It is found that the influence of the hyperon-nucleon interaction on the free $\mathrm{\Lambda }$ and ${\mathrm{\Xi }}^{-}$ production is negligible. However, the large hyperfragment yields are obvious with the attractive potential. The production of double strangeness hyperfragments is reduced below $1\mu \text{b}$ in comparison to the yields of $\mathrm{\Lambda }$ hyperfragments with cross sections of 0.05–0.1 mb in antiproton induced reactions on ${}^{63}\mathrm{Cu}$ at incident momenta of 1–5 $\mathrm{GeV}/c$. The light hyperfragments are formed in the dynamical fragmentation process. The energy dependence of hyperfragment formation is weak once the incident energy is above the threshold energy for the hyperon production.

We investigate $\varphi$-meson electroproduction off the proton target, i.e., ${\gamma }^{*}p\to \varphi p$, by employing a tree-level effective Lagrangian approach in the kinematical ranges of $Q^2=(0–4) {\mathrm{GeV}}^2$, $W=(2–5)$ GeV, and $\left|t\right|\le 2{\mathrm{GeV}}^2$. In addition to the universally accepted Pomeron exchange, we consider various meson exchanges in the $t$ channel with the Regge method. Direct $\varphi$-meson radiations in the $s$- and $u$-channels are also taken into account. We find that the $Q^2$ dependence of the transverse (${\sigma }_{\mathrm{T}}$) and longitudinal (${\sigma }_{\mathrm{L}}$) cross sections are governed by Pomeron and ($a_0,f_0$) scalar-meson exchanges, respectively. Meanwhile, the contributions of $(\pi ,\eta )$ pseudoscalar- and $f_1\left(1285\right)$ axial-vector-meson exchanges are much more suppressed. The results of the interference cross sections (${\sigma }_{\mathrm{LT}},{\sigma }_{\mathrm{LT}}$) and the spin-density matrix elements indicate that $s$-channel helicity conservation holds at $Q^2=(1–4) {\mathrm{GeV}}^2$. The result of the parity asymmetry yield $P\simeq 0.95$ at $W=2.5$ GeV, meaning that natural-parity exchange dominates the reaction process. Our numerical results are in fair agreement with the experimental data and thus the use of our effective Reggeized model is justified over the considered kinematical ranges of $Q^2,W$, and $t$.

We investigate the sensitivity of the nonexclusive nucleon induced deuteron breakup reaction to the three-nucleon interaction and distributions of three-nucleon force effects in inclusive spectra. To this end we solve the three-nucleon Faddeev equation at a number of incoming nucleon laboratory energies using the CD Bonn nucleon-nucleon interaction alone or combined with the $2\pi$-exchange Tucson-Melbourne three-nucleon force. Based on these solutions, energy spectra of an outgoing nucleon, at a specified detection angle as well as spectra integrated over that angle, are calculated. By integrating the spectra at a given angle over the energy of the outgoing nucleon the angular distributions of three-nucleon force effects in the breakup process are additionally obtained. Contrary to elastic nucleon-deuteron scattering, where at higher energies significant three-nucleon force effects were encountered for scattering angles around the minimum of the cross section, for the breakup process only moderate effects are found and they are restricted to forward angles. Results of the present investigation show that the large three-nucleon force effects found for some specific complete breakup configurations are reduced substantially in the incomplete spectra when averaging over contributing complete geometries is performed.

Magnetic-field effects on free nucleons are studied in peripheral collisions of ${}^{197}\mathrm{Au}+{}^{197}\mathrm{Au}$ at energies ranging from 600 to 1500 MeV/nucleon by utilizing an isospin-dependent quantum molecular-dynamics (IQMD) model. With the help of angular distributions and two-particle angular correlators, the magnetic-field effect at an impact parameter of 11 fm is found to be more obvious than at an impact parameter of 8 fm. Moreover, the results suggest that, with an increase in the number of peripheral collisions, protons are more easily condensed with the magnetic field. Magnetic-field effects are further investigated by the ratio of free neutrons to free protons as functions of a two-particle correlator $C_2$, four-particle correlator $C_4$, and six-particle correlator $C_6$ of angle $\varphi$, rapidity $Y$, and transverse momentum $p_T$. The results show that weak magnetic-field effects could be revealed more clearly by these multiple-particle correlators, with the larger number of particle correlators demonstrating a clear signal. The results highlight a new method to search for weak signals using multiparticle correlators.

Background: Neutrino-driven ejecta in core collapse supernovae (CCSNe) offer an interesting astrophysical scenario where lighter heavy elements between Sr and Ag can be synthesized. Previous studies emphasized the important role that $\left(\alpha ,n\right)$ reactions play in the production of these elements, particularly in neutron-rich and alpha-rich environments.

Purpose: In this paper, we have investigated the sensitivity of elemental abundances to specific $\left(\alpha ,n\right)$ reaction-rate uncertainties under different astrophysical conditions.

Method: The abundances of lighter heavy elements were calculated with a reaction network under different astrophysical conditions. $\left(\alpha ,n\right)$ reaction rates were varied within their theoretical uncertainty by using a Monte Carlo approach.

Results: The most important $\left(\alpha ,n\right)$ reaction affecting the nucleosynthesis of lighter heavy nuclei were identified for 36 representative conditions of CCSNe neutrino-driven winds.

Conclusions: Experimental studies of these reactions will reduce the nucleosynthesis uncertainties and make it possible to use observations to understand the origin of lighter heavy elements and the astrophysical conditions where they are formed.

Nuclear level densities in ${}^{94,96,98}\mathrm{Mo}$ and ${}^{160,162,164}\mathrm{Dy}$ isotopes are calculated using the single-particle spectrum obtained with the Woods-Saxon potential. The level-density parameters, spin cut-off factors, and moments of inertia are studied. Using the available experimental data at low excitation energies, the collective enhancements of the level densities are calculated and compared with those of the phenomenological model. In Mo isotopes, these semiempirical calculations agree better with the experiments in comparison to the phenomenological model assuming a spherical shape.

In neutron star matter, there exist ${}^{1}S_0$ superfluids in lower density in the crust while ${}^{3}P_2$ superfluids are believed to exist at higher density deep inside the core. In the latter, depending on the temperature and magnetic field, either the uniaxial nematic phase, the ${\mathrm{D}}_2$-biaxial nematic phase, or the ${\mathrm{D}}_4$-biaxial nematic (${\mathrm{D}}_4$-BN) phase appears. In this paper, we discuss a mixture of the ${}^{1}S_0$ and ${}^{3}P_2$ superfluids and find their coexistence. Adopting the loop expansion and the weak-coupling approximation for the interaction between two neutrons, we obtain the Ginzburg-Landau (GL) free energy in which both of the ${}^{1}S_0$ and ${}^{3}P_2$ condensates are taken into account by including the coupling terms between them. We analyze the GL free energy and obtain the phase diagram for the temperature and magnetic field. We find that the ${}^{1}S_0$ superfluid excludes the ${}^{3}P_2$ superfluid completely in the absence of magnetic field, they can coexist for weak magnetic fields, and the ${}^{1}S_0$ superfluid is expelled by the ${}^{3}P_2$ superfluid at strong magnetic fields, thereby proving the robustness of ${}^{3}P_2$ superfluid against the magnetic field. We further show that the ${\mathrm{D}}_4$-BN phase covers the whole region of the ${}^{3}P_2$ superfluidity as a result of the coupling term, in contrast to the case of a pure ${}^{3}P_2$ superfluid studied before in which the ${\mathrm{D}}_4$-BN phase is realized only under strong magnetic fields. Thus, the ${\mathrm{D}}_4$-BN phase is topologically the most interesting phase, e.g., admitting half-quantized non-Abelian vortices relevant not only in magnetars but also in ordinary neutron stars.

We study breakup of the deuteron induced by neutrinos in the neutral $\nu d\to \nu np$, $\overline{\nu }d\to \overline{\nu }np$ and the charged $\overline{\nu }d\to e^{+}nn$, $\nu d\to e^{-}pp$ processes. Pionless effective field theory with dibaryon fields is used to calculate the total cross sections for neutrino energies $E_{\nu }$ from threshold to 20 MeV. Amplitudes are expanded up to next-to-leading order, and the partial waves are truncated at $P$ waves. The Coulomb interaction between two protons is included nonperturbatively in the reaction amplitudes, and an analytic expression of the amplitudes is obtained. The next-to-leading order contribution to the total cross section is in the range of $5.2–9.9$% in magnitude and that of the $P$ waves is $2.4–2.8$% at $E_{\nu }=20$ MeV. Uncertainty arising from an axial isovector low-energy constant is estimated to be on the order of 1%.

Excited states in ${}^{174}\mathrm{Re}$ have been populated in fusion-evaporation reactions at the Australian National University, and $\gamma$-ray spectroscopy has been used to determine the level structure and to deduce the underlying nucleon configurations. The half-life of the bandhead of the $K^{\pi }=8^{-}$ band has been measured to be 2.7(4) ns. A band built on an isomeric state of spin-parity (${14}^{-}$) and a half-life of 53(5) ns has been observed here for the first time, and has been determined to have a four-quasiparticle structure. Contrasting reduced-hindrance values for its decay are discussed in terms of deformation and configuration changes, as indicated by configuration-constrained potential energy surface calculations.

Static and dynamical aspects of nuclear systems are described through an extended time-dependent mean-field approach. The foundations of the formalism are presented, with highlights on the estimation of average values and their corresponding dispersions. In contrast to semiclassical transport models, the particular interest of this description lies on its intrinsic quantal character. The reliability of this approach is discussed by means of stopping-sensitive observables analysis in heavy-ion collisions in the range of 20 to 120 MeV per nucleon.

Background: Breakup reactions are often used to probe the nuclear structure of halo nuclei. The eikonal model diverges for Coulomb breakup since it relies on the adiabatic approximation. To correct this weakness, a Coulomb-corrected eikonal method (CCE) using the Coulomb first-order-perturbation approximation was developed.

Purpose: Since the CCE mixes two reaction models and treats the Coulomb and nuclear interactions on different footings, we study here an alternative approach. We develop a simplification to the dynamical eikonal approximation (S-DEA) which has a similar numerical cost as the usual eikonal model, and study its efficiency for both nuclear- and Coulomb-dominated breakup reactions.

Methods: We compare the energy and parallel-momentum cross sections obtained with the dynamical eikonal approximation, the usual eikonal approximation, the CCE, and the S-DEA.

Results: The S-DEA leads to precise energy distributions for both breakup reactions. The corresponding parallel-momentum distributions obtained with the S-DEA are improved compared to the ones computed with the usual eikonal model. It is more efficient for nuclear-dominated breakup than the CCE since it reproduces better the shape and magnitude of the distribution. However, for the Coulomb breakup, the distribution lacks asymmetry.

Conclusions: The simplification of the DEA developed in this work improves significantly the eikonal descriptions of breakup energy distribution for both Coulomb- and nuclear-dominated reactions. The asymmetry of the parallel-momentum distribution is enhanced for nuclear-dominated breakup. This study confirms that the asymmetry is due to dynamical effects. A direct prospect of this work would be to extend this model to two-neutron halo-nucleus projectiles.

The hyperfine splitting of the $5g\to 4f$ transitions in muonic ${}^{185,187}\mathrm{Re}$ has been measured using high resolution high purity germanium detectors and compared to state-of-the-art atomic theoretical predictions. The spectroscopic quadrupole moment has been extracted using modern fitting procedures and compared to the values available in literature obtained from muonic x rays of natural rhenium. The extracted values of the nuclear spectroscopic quadrupole moment are 2.07(5) b and 1.94(5) b, respectively for ${}^{185}\mathrm{Re}$ and ${}^{187}\mathrm{Re}$.

We analyze magnetic and axial two-nucleon contact terms in a combined large-$N_c$ and pionless effective field theory expansion. These terms play important roles in correctly describing, e.g., the low-energy cross section of radiative neutron capture and the deuteron magnetic moment. We show that the large-$N_c$ expansion hints towards a hierarchy between the two leading-order magnetic terms that matches that found in phenomenological fits. We also comment on the issue of naturalness in different Lagrangian bases.

The radionuclide ${}^{22}\mathrm{Na}$ is a target of $\gamma$-ray astronomy searches, predicted to be produced during thermonuclear runaways driving classical novae. The ${}^{22}\mathrm{Na}(p,\gamma ){}^{23}\mathrm{Mg}$ reaction is the main destruction channel of ${}^{22}\mathrm{Na}$ during a nova, hence, its rate is needed to accurately predict the ${}^{22}\mathrm{Na}$ yield. However, experimental determinations of the resonance strengths have led to inconsistent results. In this Rapid Communication, we report a measurement of the branching ratios of the ${}^{23}\mathrm{Al}\beta$-delayed protons as a probe of the key 204-keV (center-of-mass) ${}^{22}\mathrm{Na}(p,\gamma ){}^{23}\mathrm{Mg}$ resonance strength. We report a factor of 5 lower branching ratio compared to the most recent literature value. The variation in ${}^{22}\mathrm{Na}$ yield due to nuclear data inconsistencies was assessed using a series of hydrodynamic nova outburst simulations and has increased to a factor of 3.8, corresponding to a factor of $\approx 2$ uncertainty in the maximum detectability distance. This is the first reported scientific measurement using the Gaseous Detector with Germanium Tagging system.

Background: Neutron-rich nuclei in the mass region around $A=160$ have been and will continue to be of interest for the study of nuclear structure because of the rapid onset of deformation between 88 and 90 neutrons. The observation of detailed changes in nuclear structures within this mass region has provided and will continue to provide insight into the nuclear force.

Purpose: Investigations of $\gamma$ rays emitted following ${}^{163}\mathrm{Eu} \beta$-decay to ${}^{163}\mathrm{Gd}$ have been performed for evaluation of the nuclear structure of ${}^{163}\mathrm{Gd}$.

Method: Data were collected at the LeRIBSS station of the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory with an array of four Clover HPGe detectors for $\gamma$-rays and two plastic scintillators for $\beta$ detection. The $\gamma$ rays were identified as belonging to ${}^{163}\mathrm{Gd}$ via mass selection and $\gamma -\gamma -\beta$, x-ray-$\gamma$, or $\gamma -\gamma$ coincidences.

Results: In total 107 new $\gamma$-ray transitions were observed in ${}^{163}\mathrm{Gd}$ from 53 newly identified levels.

Conclusions: The structure of ${}^{163}\mathrm{Gd}$ has been identified for the first time. This structure has been evaluated in comparison to projected shell model, and potential energy surface calculations with good agreement.

We construct the equation of state for high-density neutron star matter at zero temperature using the two-flavor Nambu–Jona-Lasinio (NJL) model as an effective theory of QCD. We build nuclear matter, quark matter, and the mixed phases from the same NJL Lagrangian, which has been used to model free and in-medium hadrons as well as nuclear systems. A focus here is to determine if the same coupling constants in the scalar diquark and vector meson channels, which give a good description of nucleon structure and nuclear matter, can also be used for the color superconducting high-density quark matter phase. We find that this is possible for the scalar diquark (pairing) interaction, but the vector meson interaction has to be reduced so that superconducting quark matter becomes the stable phase at high densities. We compare our equation of state with recent phenomenological parametrizations based on generic stability conditions for neutron stars. We find that the maximum mass of a hybrid star, with a color superconducting quark matter core, exceeds $2.01\pm 0.04M_{\odot }$, which is the value of the recently observed massive neutron star PSR $\text{J0348}+0432$. The mass-radius relation is also consistent with gravitational wave observations (GW170817).

Background: ${}^{40}\mathrm{K}$ plays a significant role in the radiogenic heating of Earth-like exoplanets, which can affect the development of a habitable environment on their surfaces. The initial amount of ${}^{40}\mathrm{K}$ in the interior of these planets depends on the composition of the interstellar clouds from which they formed. Within this context, nuclear reactions that regulate the production of ${}^{40}\mathrm{K}$ during stellar evolution can play a critical role.

Purpose: In this study, we constrain for the first time the astrophysical reaction rate of ${}^{40}\mathrm{K}(n,p){}^{40}\mathrm{Ar}$, which is responsible for the destruction of ${}^{40}\mathrm{K}$ during stellar nucleosynthesis. We provide to the nuclear physics community high-resolution data on the cross section and angular distribution of the ${}^{40}\mathrm{Ar}(p,n){}^{40}\mathrm{K}$ reaction. These are important to various applications involving ${}^{40}\mathrm{Ar}$. The associated reaction rate of the ${}^{40}\mathrm{Ar}(p,n){}^{40}\mathrm{K}$ process addresses a reaction rate gap in the Joint Institute for Nuclear Astrophysics REACLIB database in the region of intermediate-mass isotopes.

Methods: We performed differential cross-section measurements on the ${}^{40}\mathrm{Ar}(p,n){}^{40}\mathrm{K}$ reaction, for six energies in the center-of-mass system between 3.2 and 4.0 MeV and various angles between $0^{\circ }$ and ${135}^{\circ }$. The experiment took place at the Edwards Accelerator Laboratory at Ohio University using the beam swinger target location and a standard neutron time-of-flight technique. We extracted total and partial cross sections by integrating the double differential cross sections we measured.

Results: The total and partial cross sections varied with energy due to the contribution from isobaric analog states and Ericson type fluctuations. The energy-averaged neutron angular distributions were symmetrical relative to ${90}^{\circ }$. Based on the experimental data, local transmission coefficients were extracted and were used to calculate the astrophysical reaction rates of ${}^{40}\mathrm{Ar}(p,n){}^{40}\mathrm{K}$ and ${}^{40}\mathrm{K}(n,p){}^{40}\mathrm{Ar}$ reactions. The new rates were found to vary significantly from the theoretical rates in the REACLIB library. We implemented the new rates in network calculations to study nucleosynthesis via the slow neutron capture process, and we found that the produced abundance of ${}^{40}\mathrm{K}$ is reduced by up to 10% compared to calculations with the library rates. At the same time, the above result removes a significant portion of the previous theoretical uncertainty on the ${}^{40}\mathrm{K}$ yields from stellar evolution calculations.

Conclusions: Our results support a destruction rate of ${}^{40}\mathrm{K}$ in massive stars via the ${}^{40}\mathrm{K}(n,p){}^{40}\mathrm{Ar}$ reaction that is larger compared to previous estimates. The rate of ${}^{40}\mathrm{K}$ destruction via the ${}^{40}\mathrm{K}(n,p){}^{40}\mathrm{Ar}$ reaction now has a dramatically reduced uncertainty based on our measurement. This result directly affects the predicted stellar yields of ${}^{40}\mathrm{K}$ from nucleosynthesis, which is a critical input parameter for the galactic chemical evolution models that are currently employed for the study of significant properties of exoplanets.

The $\beta$ decay of ${}^{207}\mathrm{Hg}$ into the single-proton-hole nucleus ${}^{207}\mathrm{Tl}$ has been studied through $\gamma$-ray spectroscopy at the ISOLDE Decay Station (IDS) with the aim of identifying states resulting from coupling of the $\pi s_{1/2}^{-1}$, $\pi d_{3/2}^{-1}$, and $\pi h_{11/2}^{-1}$ shell model orbitals to the collective octupole vibration. Twenty-two states were observed lying between 2.6 and 4.0 MeV, eleven of which were observed for the first time, and 78 new transitions were placed. Two octupole states ($s_{1/2}$-coupled) are identified and three more states ($d_{3/2}$-coupled) are tentatively assigned using spin-parity inferences, while further $h_{11/2}$-coupled states may also have been observed for the first time. Comparisons are made with state-of-the-art large-scale shell model calculations and previous observations made in this region, and systematic underestimation of the energy of the octupole vibrational states is noted. We suggest that in order to resolve the difference in predicted energies for collective and noncollective $t=1$ states ($t$ is the number of nucleons breaking the ${}^{208}\mathrm{Pb}$ core), the effect of $t=2$ mixing may be reduced for octupole-coupled states. The inclusion of mixing with $t=0,2,3$ excitations is necessary to replicate all $t=1$ state energies accurately.