The ${}^{34}\mathrm{Ar}(\alpha ,p){}^{37}\mathrm{K}$ reaction is believed to be one of the last in a sequence of ($\alpha ,p$) and ($p,\gamma$) reactions within the $T_z=-1, sd$-shell nuclei, known as the $\alpha p$-process. This process is expected to influence the shape and rise times of luminosity curves coming from type I x-ray bursts (XRBs). With very little experimental information known on many of the reactions within the $\alpha p$-process, stellar rates are calculated using a statistical model, such as Hauser-Feshbach. Questions on the applicability of a Hauser-Feshbach model for the ${}^{34}\mathrm{Ar}(\alpha ,p){}^{37}\mathrm{K}$ reaction arise due to level density considerations in the compound nucleus, ${}^{38}\mathrm{Ca}$. We have performed high energy-resolution forward-angle ${}^{40}\mathrm{Ca}(p,t){}^{38}\mathrm{Ca}$ measurements with the $K=600$ spectrograph at iThemba LABS in order to identify levels above the $\alpha$-threshold in ${}^{38}\mathrm{Ca}$. States identified in this work were then used to determine the ${}^{34}\mathrm{Ar}(\alpha ,p){}^{37}\mathrm{K}$ reaction rate based on a narrow-resonance formalism. Comparisons are made to two standard Hauser-Feshbach model predicted rates at XRB temperatures.

We further progress along the line of Ref. [D. Lacroix, Phys. Rev. A 94, 043614 (2016)] where a functional for Fermi systems with anomalously large $s$-wave scattering length $a_s$ was proposed that has no free parameters. The functional is designed to correctly reproduce the unitary limit in Fermi gases together with the leading-order contributions in the $s$- and $p$-wave channels at low density. The functional is shown to be predictive up to densities $\sim 0.01 {\mathrm{fm}}^{-3}$ that is much higher densities compared to the Lee-Yang functional, valid for $\rho <{10}^{-6} {\mathrm{fm}}^{-3}$. The form of the functional retained in this work is further motivated. It is shown that the new functional corresponds to an expansion of the energy in $\left(a_s{k}_F\right)$ and $\left(r_e{k}_F\right)$ to all orders, where $r_e$ is the effective range and $k_F$ is the Fermi momentum. One conclusion from the present work is that, except in the extremely low-density regime, nuclear systems can be treated perturbatively in $-{\left(a_s{k}_F\right)}^{-1}$ with respect to the unitary limit. Starting from the functional, we introduce density-dependent scales and show that scales associated with the bare interaction are strongly renormalized by medium effects. As a consequence, some of the scales at play around saturation are dominated by the unitary gas properties and not directly by low-energy constants. For instance, we show that the scale in the $s$-wave channel around saturation is proportional to the so-called Bertsch parameter ${\xi }_0$ and becomes independent of $a_s$. We also point out that these scales are of the same order of magnitude than those empirically obtained in the Skyrme energy density functional. We finally propose a slight modification of the functional such that it becomes accurate up to the saturation density $\rho \simeq 0.16 {\mathrm{fm}}^{-3}$.

Recent classical-statistical numerical simulations have established the “bottom-up” thermalization scenario of Baier et al. [Phys. Lett. B 502, 51 (2001)] as the correct weak coupling effective theory for thermalization in ultrarelativistic heavy-ion collisions. We perform a parametric study of photon production in the various stages of this bottom-up framework to ascertain the relative contribution of the off-equilibrium “glasma” relative to that of a thermalized quark-gluon plasma. Taking into account the constraints imposed by the measured charged hadron multiplicities at Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), we find that glasma contributions are important especially for large values of the saturation scale at both energies. These nonequilibrium effects should therefore be taken into account in studies where weak coupling methods are employed to compute photon yields.

Using the test-particle method to solve the transport equation derived from the Nambu-Jona-Lasino (NJL) model, we study how phase separation occurs in expanding quark matter like that in a heavy ion collision. To test our method, we first investigate the growth rates of unstable modes of quark matter in a static cubic box and find them to agree with the analytical results that were previously obtained using the linear response theory. In this case, we also study the higher-order scaled density moments in the quark matter, which have values of 1 for a uniform density distribution or a distribution where the nonzero density regions all have same value, and they are found to increase with time and saturate at values significantly larger than 1 after the phase separation. The skewness of the quark number event-by-event distribution in a small subvolume of the system is also found to increase, but this feature disappears if the subvolume is large. For the expanding quark matter, two cases are considered: one using a blast-wave model for the initial conditions and the other using initial conditions from a multiphase transport (AMPT) model. In both cases, we find that the expansion of the quark matter is slowed down by the presence of a first-order phase transition. Also, density clumps appear in the system and the momentum distribution of partons becomes anisotropic, which can be characterized by large scale density moments and nonvanishing anisotropic elliptic and quadrupolar flows, respectively. The large density fluctuations further lead to an enhancement in the dilepton yield. In the case with the AMPT initial conditions, the presence of a first-order phase transition also results in a narrower distribution of partons in rapidity. These effects of density fluctuations can be regarded as possible signals for a first-order phase transition that occurs in the baryon-rich quark matter formed in relativistic heavy ion collisions.

The positive-parity band of ${}^{106}\mathrm{Ag}$ has been extended up to $I=25\hslash$ and the lifetimes of the high spin levels of this band have been measured. The deduced transition rates decrease with increasing spin until $I=21\hslash$. Beyond this spin, the observed transition rates are substantially small and remain nearly constant. This is a novel observation for a shears band. The observed features have been described within the framework of the shears mechanism with a principle axis cranking calculation.

The $\gamma$ decays of excited states in the very neutron-rich nucleus ${}^{88}\mathrm{Se}$ have been observed following the neutron-induced fission of ${}^{235}\mathrm{U}$. The measurement was performed using the EXILL array of Ge detectors at the PF1B cold-neutron beam facility of the Institut Laue-Langevin, Grenoble. The level scheme of ${}^{88}\mathrm{Se}$ was established using $\gamma \text{−}\gamma \text{−}\gamma$ coincidences. A low $\left(2_1^{+}\right)$ energy hints at the onset of quadrupole deformation, and the identification of possible members of a $\left(2_2^{+}\right)$ band provide evidence for $\gamma$ vibrations. Shell-model calculations using a ${}^{78}\mathrm{Ni}$ core reproduce the decay scheme well. Equivalent deformation and $B\left(E2\right)$ values have previously been predicted for ${}^{88}\mathrm{Se}$ using pseudo-SU(3), shell-model, and beyond mean-field frameworks implying that interactions between particles in the $\pi f_{5/2}p$ and $\nu sd$ orbits are mostly responsible for the collectivity present.

A study of parameter sensitivity of nuclear energy density functionals, initiated in the first part of this work [Nikšić and Vretenar, Phys. Rev. C 94, 024333 (2016)], is extended by the inclusion of data on ground-state properties of finite nuclei in the application of the manifold boundary approximation method (MBAM). Density functionals used in self-consistent mean-field calculations, and nuclear structure models based on them, are generally “sloppy” and exhibit an exponential range of sensitivity to parameter variations. Concepts of information geometry are used to identify the presence of effective functionals of lower dimension in parameter space associated with parameter combinations that can be tightly constrained by data. The MBAM is used in an iterative procedure that systematically reduces the complexity and dimension of parameter space of a sloppy functional, with properties of nuclear matter and data on finite nuclei determining not only the values of model parameters but also the optimal functional form of the density dependence.

The definitions of nuclear surface and nuclear radii are considered within the Gibbs-Tolman-Rowlinson-Widom (GTW) approach. We demonstrate the nonmonotonic behavior of the nuclear equimolar radii, which is due to the shell effects in the chemical potential of finite nuclei. The direct variational method within the extended Thomas-Fermi approximation is used to establish the equation of state for finite nuclei. We have studied the influence of the polarization effect caused by the neutron excess on the particle density and the nuclear radii. This effect increases with the asymmetry parameter $X$ and can be responsible for the appearance of large neutron halos in nuclei well away from the $\beta$ stability line. We have performed new calculations of the $A$ dependence of the radii $R\left(A\right)$ of nucleon distribution, which are based on the use of the experimental data for the nuclear binding energy. We demonstrate the presence of the quantum shell effects in $R\left(A\right)$. We have analyzed the value of the neutron-skin thickness $\mathrm{\Delta }{r}_{np}$ in the isotopes of the Na, Sn, and Pb nuclei within the GTW approach and show the appearance of nonmonotonic behavior of $\mathrm{\Delta }{r}_{np}$ as a function of the neutron excess. We discuss the relative contributions to the neutron-skin thickness $\mathrm{\Delta }{r}_{np}$ from the skin and the halo effects.

A set of global phenomenological optical model potential parameters for ${}^8\mathrm{Li}$ projectile is obtained by fitting the experimental data of ${}^8\mathrm{Li}$ elastic-scattering angular distributions from ${}^9\mathrm{Be}$ to ${}^{208}\mathrm{Pb}$ targets with incident energies between 11.0 and 33.1 MeV. By using the global optical model potential obtained, the elastic-scattering angular distributions are calculated and compared with the available experimental data. It is shown that the ${}^8\mathrm{Li}$ global potential can achieve satisfactory reproduction of the experiment.

We discuss the implementation of leading-order photon production in nonequilibrium partonic transport simulations. In this framework photons are produced by microscopic scatterings, where we include the exact matrix elements of Compton scattering, quark-antiquark annihilation, and bremsstrahlung processes. We show how the hard-thermal loop inspired screening of propagators has to be modified such that the microscopic production rate agrees well with the analytically known resummed leading-order rate. We model the complete quark-gluon plasma phase of heavy-ion collisions by using the partonic transport approach called the Boltzmann approach to multiparton scatterings (BAMPS), which solves the ultrarelativistic Boltzmann equation with Monte Carlo methods. We show photon spectra and elliptic flow of photons from BAMPS and discuss nonequilibrium effects. Due to the slow quark chemical equilibration in BAMPS, the yield is lower than the results from other groups; in turn we see a strong effect from scatterings of energetic jet-like partons with the medium. This nonequilibrium photon production can dominate the thermal emission, such that the spectra are harder and the photonic elliptic flow of the quark-gluon plasma becomes negative.

We investigate the hidden strange light baryon-meson system. With the resonating-group method, two bound states, ${\eta }^{\prime }-N$ and $\varphi -N$, are found in the quark delocalization color screening model. Focusing on the $\varphi -N$ bound state around 1950 MeV, we obtain the total decay width of about 4 MeV by calculating the phase shifts in the resonance scattering processes. To study the feasibility of an experimental search for the $\varphi -N$ bound state, we perform a Monte Carlo simulation of the bound state production with an electron beam and a gold target. In the simulation, we use the CLAS12 detector with the Forward Tagger and the BONUS12 detector in Hall B at Jefferson Lab. Both the signal and the background channels are estimated. We demonstrate that the signal events can be separated from the background with some momentum cuts. Therefore it is feasible to experimentally search for the $\varphi -N$ bound state through the near threshold $\varphi$ meson production from heavy nuclei.

We present a thermodynamically consistent method by which equations of state based on nonrelativistic potential models can be modified so that they respect causality at high densities, both at zero and finite temperature (entropy). We illustrate the application of the method by using the high-density phase parametrization of the well-known Akmal–Pandharipande–Ravenhall model in its pure neutron matter configuration as an example. We also show that, for models with only contact interactions, the adiabatic speed of sound is independent of the temperature in the limit of very large temperature. This feature is approximately valid for models with finite-range interactions as well, insofar as the temperature dependence they introduce to the Landau effective mass is weak. In addition, our study reveals that in first-principle nonrelativistic models of hot and dense matter, contributions from higher-than-two-body interactions must be screened at high density to preserve causality.

In a previous study of the collective multiphonon bands in ${}^{154}\mathrm{Gd}$, using the microscopic dynamic pairing plus quadrupole model, data for eight $K$ bands were analyzed. In the last four decades, its decay scheme is significantly revised and the nuclear theory has undergone a significant change. Special focus is on new weak intensity transitions in several bands and on the reassigned levels in its decay scheme. The present study represents a detailed revised analysis of the collective even parity bands below 2.1 MeV. Also, a discussion is given on the nature of the $K^{\pi }=0^{+}$ excited bands, validity of band mixing approach, and of the assumption of shape coexistence of β band with ground band. Comparison is made with the $X$(5) analytical symmetry and the algebraic interacting boson model predictions. Discussion of the $2n$ transfer reactions is given. The validity of the multiphonon view of the $K^{\pi }=4^{+}$ and $2_2^{+}$ bands is also studied.

The system created in ultrarelativistic nuclear collisions is known to behave as an almost ideal liquid. In noncentral collisions, because of the large orbital momentum, such a system might be the fluid with the highest vorticity ever created under laboratory conditions. Particles emerging from such a highly vorticous fluid are expected to be globally polarized with their spins on average pointing along the system angular momentum. Vorticity-induced polarization is the same for particles and antiparticles, but the intense magnetic field generated in these collisions may lead to the splitting in polarization. In this paper we outline the thermal approach to the calculation of the global polarization phenomenon for particles with spin and we discuss the details of the experimental study of this phenomenon, estimating the effect of feed-down. A general formula is derived for the polarization transfer in two-body decays and, particularly, for strong and electromagnetic decays. We find that accounting for such effects is crucial when extracting vorticity and magnetic field from the experimental data.

The ability to separately identify the Cherenkov and scintillation light components produced in scintillating mediums holds the potential for a major breakthrough in neutrino detection technology, allowing development of a large, low-threshold, directional detector with a broad physics program. The CHESS (CHErenkov/Scintillation Separation) experiment employs an innovative detector design with an array of small, fast photomultiplier tubes and state-of-the-art electronics to demonstrate the reconstruction of a Cherenkov ring in a scintillating medium based on photon hit time and detected photoelectron density. This paper describes the physical properties and calibration of CHESS along with first results. The ability to reconstruct Cherenkov rings is demonstrated in a water target, and a time precision of $338\pm 12\mathrm{ps}$ FWHM is achieved. Monte Carlo–based predictions for the ring imaging sensitivity with a liquid scintillator target predict an efficiency for identifying Cherenkov hits of $94\pm 1\%$ and $81\pm 1\%$ in pure linear alkyl benzene (LAB) and LAB loaded with 2 g/L of a fluor, PPO, respectively, with a scintillation contamination of $12\pm 1\%$ and $26\pm 1\%$.

A systematic search of triaxial ground state and shape coexistence in Ru and Mo isotopes is done using the relativistic-Hartree-Bogoliubov formalism using density-dependent zero and finite range $NN$ interactions, and with separable pairing. Shape coexistence and triaxiality softness manifest themselves in a clear manner in Mo isotopes and only triaxiality softness is very clear in all of the Ru isotopes. Both point-coupling and meson-exchange models give similar results with few exceptions. A very good 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.

The cross sections for the reaction ${}^{76}\mathrm{Ge}(n,2n){}^{75}\mathrm{Ge}$ to both the isomeric state and the ground state of ${}^{75}\mathrm{Ge}$ have been measured with the activation method between 10 and 15 MeV in small energy steps to help resolve inconsistencies in the existing database. The ${}^{197}\mathrm{Au}(n,2n){}^{196}\mathrm{Au}$ reaction with its known cross section was used for normalization of the data, which are compared to experimental and evaluated data of the EXFOR, EAF, JENDL, ENDF, and TENDL libraries. Model calculations using the talys-1.8 code are presented which also allow for the extrapolation to higher neutron energies. The data are important to estimate potential neutron-induced backgrounds in currently running large-scale experiments aimed at the discovery of neutrinoless $\beta \beta$ decay of ${}^{76}\mathrm{Ge}$.

We present a general scheme of a shell-model analysis of a $\beta$-delayed proton emission. We show that the experimental proton to $\gamma$-ray branching ratio for the isobaric analog state (IAS) populated in $\beta$ decay of a precursor, supplemented by theoretical proton and $\gamma$-ray widths, can be used to extract spectroscopic factors for isospin-forbidden proton emission. In the case of a well-justified two-level mixing approximation and a relatively well known spectroscopic factor of the admixed state, the proposed scheme provides a new way to determine the amount of the isospin mixing in the IAS. This conjecture is illustrated by the theoretical analysis of ${}^{44}\mathrm{Cr}$ and ${}^{48}\mathrm{Fe}$ decay.

SOFIA (Studies On Fission with Aladin) is a novel experimental program, dedicated to accurate measurements of fission-fragment isotopic yields. The setup allows us to fully identify, in nuclear charge and mass, both fission fragments in coincidence for the whole fission-fragment range. It was installed at the GSI facility (Darmstadt), to benefit from the relativistic heavy-ion beams available there, and thus to use inverse kinematics. This paper reports on fission yields obtained in electromagnetically induced fission of ${}^{238}\mathrm{U}$.

Using the phenomenological quantum friction models introduced by P. Caldirola [Nuovo Cimento 18, 393 (1941)] and E. Kanai [Prog. Theor. Phys. 3, 440 (1948)], M. D. Kostin [J. Chem. Phys. 57, 3589 (1972)], and K. Albrecht [Phys. Lett. B 56, 127 (1975)], we study quantum tunneling of a one-dimensional potential in the presence of energy dissipation. To this end, we calculate the tunneling probability using a time-dependent wave-packet method. The friction reduces the tunneling probability. We show that the three models provide similar penetrabilities to each other, among which the Caldirola-Kanai model requires the least numerical effort. We also discuss the effect of energy dissipation on quantum tunneling in terms of barrier distributions.