The ground state branch of the $\beta$ decay of ${}^{66}\mathrm{Ga}$ is an allowed Fermi ($0^{+}\to 0^{+}$) transition with a relatively high $ft$ value. The large $ft$ and the isospin-forbidden nature of the transition indicates that the shape of the $\beta$ spectrum of this branch may be sensitive to higher order contributions to the decay. Two previous measurements of the shape have revealed deviations from an allowed spectrum but disagree about whether the shape factor has a positive or negative slope. As a test of a new iron-free superconducting $\beta$ spectrometer, we have measured the shape of the ground state branch of the ${}^{66}\mathrm{Ga}$ $\beta$ spectrum above a positron energy of 1.9 MeV. The spectrum is consistent with an allowed shape, with the slope of the shape factor being zero to within $\pm 3\times {10}^{-3}$ per MeV. We have also determined the endpoint energy for the ground state branch to be $4.1535\pm 0.0003$ (stat.) $\pm 0.0007$ (syst.) MeV, in good agreement with and a factor of 3 more precise than the presently accepted value.

Background: The electric isovector giant dipole resonance (IVGDR) in ${}^{208}\mathrm{Pb}$ has been measured with high energy resolution with the $(p,p^{\prime })$ reaction under extreme forward angles [A. Tamii et al., Phys. Rev. Lett. 107, 062502 (2011)] and shows considerable fine structure.

Purpose: The aim of the present work is to extract scales characterizing the observed fine structure and to relate them to dominant decay mechanisms of giant resonances. Furthermore, the level density of $J^{\pi }=1^{-}$ states is determined in the energy region of the IVGDR.

Methods: Characteristic scales are extracted from the spectra with a wavelet analysis based on continuous wavelet transforms. Comparison with corresponding analyses of $B\left(E1\right)$ strength distributions from microscopic model calculations in the framework of the quasiparticle phonon model and the relativistic random phase approximation allows one to identify giant resonance decay mechanisms responsible for the fine structure. The level density of $1^{-}$ states is related to local fluctuations of the cross sections in the energy region of the IVGDR, where contributions from states with other spin parities can be neglected. The magnitude of the fluctuations is determined by the autocorrelation function.

Results: Scales in the fine structure of the IVGDR in ${}^{208}\mathrm{Pb}$ are found at 80, 130, 220, 430, 640, and 960 keV, and at 1.75 MeV. The values of the most prominent scales can be reasonably well reproduced by the microscopic calculations although they generally yield a smaller number of scales. The inclusion of complex configurations in the calculations changes the $E1$ strength distributions but the impact on the wavelet power spectra and characteristic scales is limited. The level density of $1^{-}$ states is extracted in the excitation energy range $9–12.5$ MeV and compared to a variety of phenomenological and microscopic models.

Conclusions: In both models the major scales are already present at the one-particle one-hole level indicating Landau damping as a dominant mechanism responsible for the fine structure of the IVGDR in contrast to the isoscalar giant quadrupole resonance, where fine structure arises from the coupling to low-lying surface vibrations. The back-shifted Fermi gas model parametrization of Rauscher et al., Phys. Rev. C 56, 1613 (1997) describes the level-density data well, while other phenomenological and microscopic approaches fail to reproduce absolute values or the energy dependence or both.

In carbon therapy, the interaction of the incoming beam with human tissue may lead to the production of a large amount of nuclear fragments and secondary light particles. An accurate estimation of the biological dose on the tumor and the surrounding healthy tissue thus requires sophisticated simulation tools based on nuclear reaction models. The validity of such models requires intensive comparisons with as many sets of experimental data as possible. Up to now, a rather limited set of double differential carbon fragmentation cross sections has been measured in the energy range used in hadron therapy (up to 400 MeV/nucleon). However, new data have been recently obtained at intermediate energy (95 MeV/nucleon). The aim of this work is to compare the reaction models embedded in the geant4 Monte Carlo toolkit with these new data. The strengths and weaknesses of each tested model, i.e., G4BinaryLightIonReaction, G4QMDReaction, and INCL++, coupled to two different de-excitation models, i.e., the generalized evaporation model and the Fermi break-up model, are discussed.

The energy and angular dependence of double differential cross sections $d^2\sigma /d\Omega dE$ were measured for $p$, $d$, $t$, ${}^{3,4,6}\mathrm{He}$, ${}^{6,7,8,9}\mathrm{Li}$, ${}^{7,9,10}\mathrm{Be}$, and ${}^{10,11}\mathrm{B}$ produced in collisions of 1.2, 1.9, and 2.5 GeV protons with an Al target. It was found that the cross sections are almost independent of the beam energy. The spectra and angular distributions indicate a presence of two contributions: a quasi-isotropic, low-energy one which is attributed to the emission of particles from excited remnants of the intranuclear cascade, and an anisotropic part which is interpreted to originate from the first stage of the reaction. The experimental data are compared with an intranuclear cascade model coupled to evaporation, and to statistical multifragmentation models using their standard parameter settings. It was found that all applied models produce very similar results describing spectra of the intermediate mass fragments. All models also reproduce well the low-energy part of the spectra of light charged particles (below $\approx$ 30 MeV). The description of the higher energy part (50–150 MeV) of the light charged particles spectra is poorer, deteriorating with decreasing scattering angle and decreasing mass of the particles.

In this article we report on our results about the computation of the elliptic flow of the quark-gluon plasma produced in relativistic heavy-ion collisions, simulating the expansion of the fireball by solving the relativistic Boltzmann equation for the parton distribution function tuned at a fixed shear-viscosity to entropy-density ratio $\eta /s$. Our main goal is to put emphasis on the role of a saturation scale in the initial gluon spectrum, which makes the initial distribution far from a thermalized one. We find that the presence of the saturation scale reduces the efficiency in building up the elliptic flow, even if the thermalization process is quite fast ${\tau }_{\text{therm}}\approx 0.8\text{fm}/c$ and the pressure isotropization is even faster ${\tau }_{\text{isotr}}\approx 0.5\text{fm}/c$. The impact of the nonequilibrium implied by the saturation scale manifests for noncentral collisions and can modify the estimate of the viscosity with respect to the assumption of full thermalization in $p_T$ space. We find that the estimate of $\eta /s$ is modified from $\eta /s\approx 2/4\pi$ to $\eta /s\approx 1/4\pi$ at the Relativistic Heavy-Ion Collider and from $\eta /s\approx 3/4\pi$ to $\eta /s\approx 2/4\pi$ at the Large Hadron Collider. We complete our investigation with a study of the thermalization and isotropization times of the fireball for different initial conditions and values of $\eta /s$ showing how the latter affects both isotropization and thermalization. Last, we have seen that the range of values explored by the phase-space distribution function $f$ is such that at $p_T<0.5\mathrm{GeV}$ the inner part of the fireball stays with occupation number significantly larger than unity despite the fast longitudinal expansion, which might suggest the possibility of the formation of a transient Bose-Einstein condensate.

The $\beta$ decay of ${}^{124,126}\mathrm{Ag}$ low- and high-spin isomers into levels in ${}^{124,126}\mathrm{Cd}$ was investigated. We have greatly expanded the decay schemes in these nuclei including the identification of the $0_2^{+}$ and $0_3^{+}$ states among 63 new levels in ${}^{124}\mathrm{Cd}$ and the identification of the $2_2^{+}$ state among 30 new levels in ${}^{126}\mathrm{Cd}$. Several states were identified in ${}^{124}\mathrm{Cd}$, which based on energy are possible multiphonon states. Based on the decay of these states, we show that states in ${}^{124}\mathrm{Cd}$ behave similar to lighter Cd isotopes despite the higher intruder state energies. Our ${}^{124}\mathrm{Cd}$ data support the conclusion that the neutron-rich Cd nuclei are not described well by an anharmonic vibrator interpretation.

The sign change of the slope of the directed flow of baryons has been predicted as a signal for a first order phase transition within fluid dynamical calculations. Recently, the directed flow of identified particles was measured by the STAR Collaboration in the beam energy scan program. In this article, we examine the collision energy dependence of directed flow $v_1$ in fluid dynamical model descriptions of heavy ion collisions for $\sqrt{s_{NN}}=3$–20 GeV. The first step is to reproduce the existing predictions within pure fluid dynamical calculations. As a second step we investigate the influence of the order of the phase transition on the anisotropic flow within a state-of-the-art hybrid approach that describes other global observables reasonably well. We find that, in the hybrid approach, there seems to be no sensitivity of the directed flow on the equation of state and in particular on the existence of a first order phase transition. In addition, we explore more subtle sensitivities such as the Cooper-Frye transition criterion and discuss how momentum conservation and the definition of the event plane affects the results. At this point, none of our calculations matches qualitatively the behavior of the STAR data; the values of the slopes are always larger than in the data.

We investigate nuclear-matter equations of state in neutron stars with kaon condensation. It is generally known that the existence of kaons in neutron star makes the equation of state soft so that the maximum mass of a neutron star is not likely to be greater than $2.0M_{\odot }$, the maximum mass constrained by current observations. With existing Skyrme force model parameters, we calculate nuclear equations of state and check the possibility of kaon condensation in the core of neutron stars. The results show that, even with the kaon condensation, the nuclear equation of state satisfies both the maximum mass and the allowed ranges of mass and radius.

The total kinetic energy release in the neutron induced fission of ${}^{235}U$ was measured (using white spectrum neutrons from the Los Alamos Neutron Science Center) for neutron energies from $E_n=3.2$–50 MeV. In this energy range the average post-neutron total kinetic energy $(E_{\mathrm{TKE}}$) release drops from $167.4\pm 0.7$ to $162.1\pm 0.8$ MeV, exhibiting a local dip near the second chance fission threshold. The values and the slope of the $E_{\mathrm{TKE}}$ vs $E_n$ agree with previous measurements but disagree (in magnitude) with systematics. The variances of the $E_{\mathrm{TKE}}$ distributions are larger than expected; and apart from the structure near the second chance fission threshold, the distributions are invariant for the neutron energy range from 11 to 50 MeV. We also report the dependence of the total excitation energy in fission $(E_{\mathrm{TXE}}$) on neutron energy.

We investigate the effect of microscopic three-body forces (TBFs) on the off-shell behavior of the neutron and proton mass operators $M^{\tau }(k,\omega )=V^{\tau }(k,\omega )+i{W}^{\tau }(k,\omega )$ in asymmetric nuclear matter within the framework of the extended Brueckner-Hartree-Fock approach. We adopt the Argonne $V_{18}$ two-body potential supplemented with a microscopic TBF as the realistic nucleon-nucleon interaction. At high densities well above the normal nuclear matter density, the TBF turns out to affect significantly the off-shell behavior of both the proton and neutron mass operators. The neutron and proton spectral functions in asymmetric nuclear matter are calculated and discussed. At low densities around and below the normal density, the TBF effect on the spectral functions turns out to be negligibly weak. At high densities well above the saturation density, the TBF is shown to affect noticeably the neutron and proton spectral functions.

Covariant density functional theory is a modern theoretical tool for the description of nuclear structure phenomena. The current investigation aims at the global assessment of the accuracy of the description of the ground state properties of even-even nuclei. We also estimate theoretical uncertainties defined here as the spreads of predictions within four covariant energy density functionals in known regions of the nuclear chart and their propagation towards the neutron drip line. Large-scale axial relativistic Hartree-Bogoliubov calculations are performed for all $Z\le 104$ even-even nuclei between the two-proton and two-neutron drip lines with four modern covariant energy density functionals such as NL3*, DD-ME2, DD-ME$\delta$, and DD-PC1. The physical observables of interest include the binding energies, two-particle separation energies, charge quadrupole deformations, isovector deformations, charge radii, neutron skin thicknesses, and the positions of the two-proton and two-neutron drip lines. The predictions for the two-neutron drip line are also compared in a systematic way with the ones obtained in nonrelativistic models.

We employ a microscopic continuum-discretized coupled-channels reaction framework (MCDCC) to study the elastic angular distribution of the ${}^7\mathrm{Li}=\alpha +t$ nucleus colliding with ${}^{12}\mathrm{C}$ and ${}^{28}\mathrm{Si}$ targets at $E_{\mathrm{Lab}}=350$ MeV. In this framework, the ${}^7\mathrm{Li}$ projectile is described in a microscopic cluster model and impinges on noncomposite targets. The diagonal and coupling potentials are constructed from nucleon-target interactions and ${}^7\mathrm{Li}$ microscopic wave functions. We obtain a fair description of the experimental data, in the whole angular range studied, when continuum channels are included. The inelastic and breakup angular distributions on the lightest target are also investigated. In addition, we compute ${}^7\mathrm{Li}+{}^{12}\mathrm{C}$ MCDCC elastic cross sections at energies much higher than the Coulomb barrier and we use them as reference calculations to test the validity of multichannel eikonal cross sections.

High-statistics measurements of differential cross sections and spin density matrix elements for the reaction $\gamma p\to \varphi p$ have been made using the CLAS detector at Jefferson Lab. We cover center-of-mass energies ($\sqrt{s}$) from 1.97 to 2.84 GeV, with an extensive coverage in the $\varphi$ production angle. The high statistics of the data sample made it necessary to carefully account for the interplay between the $\varphi$ natural lineshape and effects of the detector resolution, that are found to be comparable in magnitude. We study both the charged- ($\varphi \to K^{+}{K}^{-}$) and neutral- ($\varphi \to K_S^0{K}_L^0$) $K\overline{K}$ decay modes of the $\varphi$. Further, for the charged mode, we differentiate between the cases where the final $K^{-}$ track is directly detected or its momentum reconstructed as the total missing momentum in the event. The two charged-mode topologies and the neutral-mode have different resolutions and are calibrated against each other. Extensive usage is made of kinematic fitting to improve the reconstructed $\varphi$ mass resolution. Our final results are reported in 10- and mostly 30-MeV-wide $\sqrt{s}$ bins for the charged- and the neutral-modes, respectively. Possible effects from $K^{+}{\Lambda }^{*}$ channels with $pK\overline{K}$ final states are discussed. These present results constitute the most precise and extensive $\varphi$ photoproduction measurements to date and in conjunction with the $\omega$ photoproduction results recently published by CLAS, will greatly improve our understanding of low energy vector meson photoproduction.

We perform an extensive analysis of neutrino diffusion in quark matter within the MIT bag model at arbitrary temperature and degeneracy. We examine in detail the contribution of each of the relevant weak interaction processes to the total neutrino opacity and evaluate the effect of the strange quark mass, the bag constant, and the QCD perturbative corrections to the MIT bag model. We also investigate the anisotropic contribution to the neutrino distribution function in scatterings, the mean energy transfer, and the mean scattering angle. The density and temperature dependence of the diffusion coefficients $D_n$ that govern the cooling and deleptonization of a compact star is shown in detail. Finally, our numerical results for the neutrino mean free paths are compared against known analytic approximations. We conclude that neutrino scattering constitutes a significant portion of the total neutrino opacity in leptonized quark matter, and neutrino-quark scattering is, in general, very similar to neutrino-electron scattering with respect to both mean energy transfer per scattering and mean scattering angle.

It has been recently suggested that there exists a neutral bound state of two neutrons and a $\Lambda$ hyperon, ${}_{\Lambda }^{3}n$. We point out that by using either simple separable potentials or a full-fledged calculation with realistic baryon-baryon interactions derived from the constituent quark cluster model it can be seen that there is no possibility for the existence of such a $\Lambda nn$ bound state. For this purpose, we performed a full Faddeev calculation of the $\Lambda nn$ system in the $(I,J^P)=(1,1/2^{+})$ channel using the interactions derived from the constituent quark cluster model which describes well the two-body $NN$ and $NY$ data and the $\Lambda np$ hypertriton.

We investigate the impact of pairing correlations on the behavior of unstable asymmetric nuclear matter at low temperature. We focus on the relative role of the pairing interaction, coupling nucleons of the same type (neutrons or protons), with respect to the symmetry potential, which enhances the neutron-proton attraction, along the clusterization process driven by spinodal instabilities. It is found that, especially at the transition temperature from the normal to the superfluid phase, pairing effects may induce significant variations in the isotopic content of the clusterized matter. This analysis is potentially useful for gathering information on the temperature dependence of nuclear pairing and, in general, on the properties of clusterised low-density matter, which are of interest also in the astrophysical context.

In this paper, we have analyzed the well-known quasielastic scattering data at 29 MeV/nucleon of the ${}^{11}\mathrm{Li}$ + ${}^{28}\mathrm{Si}$ system within the framework of the coupled-channels model using double-folding potential with a Woods-Saxon type of imaginary part. To explain these challenging data, we have modified the shape of the real and imaginary potentials simultaneously in the surface region and we have been able to obtain an improved agreement with the experimental data in comparison with the previous works conducted so far. Our findings confirm that the interactions in the surface region of two nuclei are very important in explaining the scattering observables of such light-heavy nuclei reactions. Our work also shows that the dynamical polarization potential should be attractive for this system.

Some 27 Hartree-Fock-Bogoliubov (HFB) mass models have been developed by the Brussels-Montreal collaboration. Each of these models has been obtained with different model prescriptions or corresponds to a significantly different minimum in the parameter space. The corresponding uncertainties in the mass extrapolation are discussed. In addition, for each of these models, uncertainties associated with local variations of the model parameters exist. Those are estimated for the HFB-24 mass model using a variant of the backward-forward Monte Carlo method to propagate the uncertainties on the masses of exotic nuclei far away from the experimentally known regions. The resulting uncertainties are found to be significantly lower than those arising from the 27 HFB mass models. In addition, the derived correlations between the calculated masses and between model parameters are analyzed.

The effect of the vector interaction on three-flavor magnetized matter is studied within the SU(3) Nambu–Jona-Lasinio quark model. We considered cold matter under a static external magnetic field within two different models for the vector interaction in order to investigate how the form of the vector interaction and the intensity of the magnetic field affect the equation of state as well as the strangeness content. It was shown that the flavor-independent vector interaction predicts a smaller strangeness content and, therefore, harder equations of state. On the other hand, the flavor-dependent vector interaction favors larger strangeness content the larger the vector coupling. We confirmed that, at low densities, the magnetic field and the vector interaction have opposite competing effects: the first one softens the equation of state while the second hardens it. Quark stars and hybrid stars subject to an external magnetic field were also studied. Larger star masses are obtained for the flavor-independent vector interaction. Hybrid stars may bare a core containing deconfined quarks if neither the vector interaction nor the magnetic field are too strong. Also, the presence of strong magnetic fields seems to disfavor the existence of a quark core in hybrid stars.