A previously published measurement of the reaction of a 59 MeV/nucleon ${}^{14}\mathrm{Be}$ beam on a deuterated polyethylene target was further analyzed to search for ${}^{12}\mathrm{He}$ as well as initial state effects in the population of the ${}^{10}\mathrm{He}$ ground state. No evidence for either was found. A lower limit of about 1 MeV was determined for a possible resonance in ${}^{12}\mathrm{He}$. In addition, the three-body decay energy spectrum of ${}^{10}\mathrm{He}$ could not be described by a reaction mechanism calculation based on the halo structure of the initial ${}^{14}\mathrm{Be}$ assuming a direct $\alpha$-particle removal reaction.

The most pronounced reaction channels in the ${}^6\mathrm{Li}+{}^{18}\mathrm{O}$ system were studied by means of the continuum-discretized coupled-channel and coupled-reaction-channel methods to investigate their effects on the elastic scattering. It is shown that, whereas breakup coupling provides no contribution to the observed rise in the backward-angle elastic scattering angular distribution, coupling to the single-neutron pickup alone enhances the elastic scattering cross section in this region by up to two orders of magnitude.

The atomic pair ${}^{163}\mathrm{Ho}$ and ${}^{163}\mathrm{Dy}$, because of its small $Q$ value of about 2.5 keV, seems to be the best pair to use to determine the neutrino mass by electron capture. The bolometer spectrum measures the full deexcitation energy of dysprosium (by x rays and Auger electrons plus the recoil of holmium, which can be neglected). The spectrum has an upper limit given by the $Q$ value minus the neutrino mass. Till now this spectrum has been calculated in dysprosium allowing excitations with $3s_{1/2}, 3p_{1/2}, 4s_{1/2}, 4p_{1/2}, 5s_{1/2}$, and $5p_{1/2}$ (and $6s_{1/2}$) holes only. Robertson [R. G. H. Robertson, arXiv:1411.2906v1] also recently calculated the spectrum with two-electron-hole excitations in Dy. He took the probability for the excitation for the second electron hole from the work of Carlson and Nestor [T. A. Carlson, C. W. Nestor, T. C. Tucker, and F. B. Malik, Phys. Rev. 169, 27 (1968); T. A. Carlson and C. W. Nestor, Phys. Rev. A 8, 2887 (1973)] for $Z=54$ xenon. The neutrino mass must finally be obtained by a simultaneous fit of the $Q$ value, together with the properties of the relevant resonances, and the neutrino mass to the the upper end of the spectrum. Under the assumption that only one resonance (independent of its nature: one-hole, two-hole, multihole, or of other origin) near the $Q$ value determines the upper end of the spectrum and that the profile of this leading state is Lorentzian, one has to fit simultaneously four parameters (neutrino mass, strength, distance of the leading resonance to the $Q$ value, and width). If more than one resonance is of comparable importance for the upper end of the spectrum, it might be difficult or even impossible to extract the neutrino mass reliably. Compared to the work of Robertson this work includes the following improvements. (i) The two-hole probabilities are calculated in the Dirac-Hartree-Fock (DHF) approach for holmium and dysprosium but not for xenon. (ii) In calculating the probability for the second electron hole in dysprosium the $n{s}_{1/2}$ or $n{p}_{1/2}$ ($n\ge 3$) one-hole states are included self-consistently in the DHF iteration. (iii) Because dysprosium has $Z=66$ electrons and xenon only has $Z=54$ electrons, one has at least eight additional two-hole states that do not exist in xenon and thus their probabilities have not been calculated by Carlson and Nestor and have not been included by Robertson. They are included here. (iv) For the probabilities of the one-hole states, which determine the main structure of the spectrum, the overlap and exchange corrections are taken into account. (v) In solving the DHF electron wave functions the finite size of the nuclear charge distribution is included. (vi) The nuclear matrix elements for electron capture integrate the charge of the captured electron over the nucleus with the weight $\psi {\left(r\right)}_{e,n,\ell ,j}^2{r}^2$. Thus, for the capture probability the value ${\psi }_{e,n,\ell ,j}^2\left(R\right)R^2$ is taken at the nuclear radius and not the value ${\psi }_{e,n,\ell ,j}^2(r=0.0)$ at $r=0.0$, which has the weight $r^2$ zero. (vii) The formulas are derived in second quantization including automatically the antisymmetrization.

The nuclear structure of the odd-mass ${}^{69}\mathrm{Zn}$ and ${}^{71}\mathrm{Zn}$ isotopes, with one hole or one particle outside the $N=40$ subshell closure, has been investigated by measuring the lifetime of excited states using the recoil distance Doppler-shift method. The nuclei of interest were produced in a deep-inelastic reaction in inverse kinematics with a ${}^{238}\mathrm{U}$ beam impinging on a ${}^{70}\mathrm{Zn}$ target. Single-particle and collective states were found to coexist at low energy in ${}^{69}\mathrm{Zn}$ and ${}^{71}\mathrm{Zn}$.

The photonuclear reactions of actinides induced by bremsstrahlung $\gamma \text{s}$ are studied in the region of nuclear excitation energies that covers the entire giant dipole resonance region. A comparative analysis of the behavior of the symmetric and asymmetric modes of photon-induced fission as a function of the average excitation energy of the fissioning nucleus is performed. The mass distributions for photofission fragments are obtained. The integrated yield as well as charge distribution of photofission products is determined. Thus, the production cross sections of neutron-rich nuclei are calculated and their exoticity (neutron richness) is explored in comparison to the nuclei produced by rapid neutron capture process in nucleosynthesis.

A recent study reports measurements of transverse-energy $E_t$ distributions at midrapidity for several high-energy nuclear collision systems. The $E_t$ data are analyzed in the context of constituent-quark (CQ) participants estimated with a Glauber-model simulation. The study concludes that systematic variations of hadron and $E_t$ yields previously interpreted in terms of a two-component $\mathrm{soft}+\mathrm{hard}$ model (TCM) of hadron production including a dijet (hard) contribution are actually the result of CQ participant trends with only soft production. It is claimed that deviations from linear scaling with the number of nucleon participants of hadron yields vs $A-A$ centrality do not actually arise from dijet production, as previously assumed. In the present study I examine the new $E_t$ data in the context of the TCM and compare those results with previous differential spectrum and minimum-bias correlation analysis. I present substantial evidence supporting a significant dijet contribution to all high-energy nuclear collisions consistent with the TCM and conclude that the $E_t$ data, given their systematic uncertainties, fail to support claimed CQ model interpretations.

Incorporating a newly improved isospin- and momentum-dependent interaction in the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model IBUU11, we have investigated relative effects of the density dependence of nuclear symmetry energy $E_{\mathrm{sym}}\left(\rho \right)$ and the neutron-proton effective mass splitting $m_n^{*}-m_p^{*}$ on the neutron-to-proton ratio of free nucleons and those in light clusters. It is found that the $m_n^{*}-m_p^{*}$ has a relatively stronger effect than the $E_{\mathrm{sym}}\left(\rho \right)$ and the assumption of $m_n^{*}\le m_p^{*}$ leads to a higher neutron-to-proton ratio. Moreover, this finding is independent of the in-medium nucleon-nucleon cross sections used. However, results of our calculations using the $E_{\mathrm{sym}}\left(\rho \right)$ and $m_n^{*}-m_p^{*}$ both within their current uncertainty ranges are all too low compared to the recent National Superconducting Cyclotron Laboratory double neutron-to-proton-ratio data from central ${}^{124}\mathrm{Sn}+{}^{124}\mathrm{Sn}$ and ${}^{112}\mathrm{Sn}+{}^{112}\mathrm{Sn}$ collisions at 50 and 120 MeV/u, thus calling for new mechanisms to explain the puzzlingly high neutron-to-proton ratio observed in the experiments.

The structure of semi-magic ${}_{28}^{70}{\mathrm{Ni}}_{42}^{}$ was investigated following complementary multinucleon-transfer and secondary fragmentation reactions. Changes to the higher-spin, presumed negative-parity states based on observed $\gamma$-ray coincidence relationships result in better agreement with shell-model calculations using effective interactions in the neutron $f_{5/2}p{g}_{9/2}$ model space. The second $2^{+}$ and $\left(4^{+}\right)$ states, however, can only be successfully described when proton excitations across the $Z=28$ shell gap are included. Monte Carlo shell-model calculations suggest that the latter two states are part of a prolate-deformed intruder sequence, establishing an instance of shape coexistence at low excitation energies similar to that observed recently in neighboring ${}^{68}\mathrm{Ni}$.

$\alpha$-particle spectra of ${}^{249}\mathrm{Cf}$ have been measured with a double-focusing magnetic spectrometer and with passivated implanted planar silicon (PIPS) detectors. The conversion-electron spectra of ${}^{249}\mathrm{Cf}$ have been measured with a cooled Si(Li) detector and with a room-temperature PIPS detector. Precise energies of $\alpha$ groups in the decay of ${}^{249}\mathrm{Cf}$ have been measured with respect to the known energy of ${}^{250}\mathrm{Cf}$. In addition, $\alpha$-electron, $\alpha \text{−}\gamma$, and $\gamma \text{−}\gamma$ coincidence measurements were also performed to determine the spin-parity of the previously known 643.64-keV level. From electron intensities, conversion coefficients of transitions in the daughter ${}^{245}\mathrm{Cm}$ have been determined. The measured $L_3$ conversion coefficients of the 333.4- and 388.2-keV transitions are found to be in agreement with the theoretical conversion coefficients for pure $E1$ multipolarity. On the other hand, the $K,L_1+L_2,M$, and $N$ conversion coefficients are approximately twice the theoretical values for pure $E1$ transitions. These measurements indicate anomalous $E1$ conversion coefficients for the 333.4- and 388.2-keV transitions, as has been pointed out in earlier measurements. The measured conversion coefficient of the 255.5-keV transition gives an $M1$ multipolarity for this transition which establishes a spin-parity of 7/$2^{-}$ and the 7/$2^{-}\left[743\right]$ single-particle assignment to the 643.64-keV level.

To exactly answer which density region that some frequently used symmetry-energy-sensitive observables probe, for the first time, we make a study of the decomposition of the sensitivity of some symmetry-energy-sensitive observables. It is found that for the Au+Au reaction at incident beam energies of 200 and 400 MeV/nucleon, frequently used symmetry-energy-sensitive observables mainly probe the density-dependent symmetry energy around $1.25{\rho }_0$ (for pionic observables) or $1.5{\rho }_0$ (for nucleonic observables). Effects of the symmetry energy in the low-density region is in general small but observable. The fact that the symmetry-energy-sensitive observables are not sensitive to the symmetry energy in the maximal baryon-density region increases the difficulty of studying nuclear symmetry energy at superdensity.

We analyze the energy dependence of the interacting optical potential, at near barrier energies, for two systems involving the weakly bound projectile ${}^9\mathrm{Be}$ and the heavy ${}^{208}\mathrm{Pb}$ and ${}^{209}\mathrm{Bi}$ targets, by the simultaneous fit of elastic scattering angular distributions and fusion excitation functions. The approach used consists of dividing the optical potential into two parts. A short-range potential $V_F+i{W}_F$ that is responsible for fusion, and a superficial potential $V_{\mathrm{DR}}+i{W}_{\mathrm{DR}}$ for direct reactions. It is found, for both systems studied, that the fusion imaginary potential $W_F$ presents the usual threshold anomaly (TA) observed in tightly bound systems, whereas the direct reaction imaginary potential $W_{\mathrm{DR}}$ shows a breakup threshold anomaly (BTA) behavior. Both potentials satisfy the dispersion relation. The direct reaction polarization potential predominates over the fusion potential and so a net overall behavior is found to follow the BTA phenomenon.

Fluctuations in the initial transverse energy-density distribution lead to anisotropic flows as observed in central high-energy heavy-ion collisions. Studies of longitudinal fluctuations of the anisotropic flows can shed further light on the initial conditions and dynamical evolution of the hot quark-gluon matter in these collisions. Correlations between anisotropic flows with varying pseudorapidity gaps in $\mathrm{Pb}+\mathrm{Pb}$ collisions at the CERN Large Hadron Collider are investigated using both an event-by-event $\left(3+1\right)$-dimensional ideal hydrodynamical model with fluctuating initial conditions and a multiphase transport (AMPT) Monte Carlo model for high-energy heavy-ion collisions. Anisotropic flows at different pseudorapidities are found to become significantly decorrelated with increasing pseudorapidity gaps due to longitudinal fluctuations in the initial states of heavy-ion collisions. The longitudinal correlation of the elliptic flow shows a strong centrality dependence while the correlation of the triangular flow is independent of the centrality. Longitudinal fluctuations as a source of the decorrelation are further shown to consist of a twist or gradual rotation in flow angles between the forward and backward direction and additional fluctuations on top of the twist. Within the AMPT model, longitudinal correlations of anisotropic flows are also found to depend on the value of partonic cross sections. The implications of constraining the initial conditions and shear viscosity to entropy density ratio of the partonic matter in high-energy heavy-ion collisions are also discussed.

Differential cross sections of the exclusive process $ep\to e^{\prime }{\pi }^{+}n$ were measured with good precision in the range of the photon virtuality $Q^2=1.8–4.5$ ${\mathrm{GeV}}^2$ and the invariant mass range of the ${\pi }^{+}n$ final state $W=1.6–2.0$ GeV using the Continuous Electron Beam Accelerator Facility Large Acceptance Spectrometer. Data were collected with nearly complete coverage in the azimuthal and polar angles of the $n{\pi }^{+}$ center-of-mass system. More than 37 000 cross-section points were measured. The contributions of the isospin $I=\frac{1}{2}$ resonances $N\left(1675\right){\frac{5}{2}}^{-},N\left(1680\right){\frac{5}{2}}^{+}$, and $N\left(1710\right){\frac{1}{2}}^{+}$ were extracted at different values of $Q^2$ using a single-channel, energy-dependent resonance amplitude analysis. Two different approaches, the unitary isobar model and the fixed-$t$ dispersion relations, were employed in the analysis. We observe significant strength of the $N\left(1675\right){\frac{5}{2}}^{-}$ in the $A_{1/2}$ amplitude, which is in strong disagreement with quark models that predict both transverse amplitudes to be strongly suppressed. For the $N\left(1680\right){\frac{5}{2}}^{+}$ we observe a slow changeover from the dominance of the $A_{3/2}$ amplitude at the real photon point $\left(Q^2=0\right)$ to a $Q^2$ where $A_{1/2}$ begins to dominate. The scalar amplitude $S_{1/2}$ drops rapidly with $Q^2$ consistent with quark model prediction. For the $N\left(1710\right){\frac{1}{2}}^{+}$ resonance our analysis shows significant strength for the $A_{1/2}$ amplitude at $Q^2<2.5$ ${\mathrm{GeV}}^2$.

We study parity violation in quasielastic electron-nucleus scattering using the relativistic impulse approximation. Different fully relativistic approaches have been considered to estimate the effects associated with the final-state interactions. We have computed the parity-violating quasielastic (PVQE) asymmetry and have analyzed its sensitivity to the different ingredients that enter into the description of the reaction mechanism: final-state interactions, nucleon off-shellness effects, and current gauge ambiguities. Particular attention has been paid to the description of the weak neutral current form factors. The PVQE asymmetry is proven to be an excellent observable when the goal is to get precise information on the axial-vector sector of the weak neutral current. Specifically, from measurements of the asymmetry at backward scattering angles good knowledge of the radiative corrections entering in the isovector axial-vector sector can be gained. Finally, scaling properties shown by the interference $\gamma -Z$ nuclear responses are also analyzed.

It is well known that coincidence quasielastic $(\vec{e},e^{\prime }N)$ reactions are not appropriate to analyze effects linked to parity violation due the presence of the fifth electromagnetic response $R^{T{L}^{\prime }}$. Nevertheless, in this work we develop a fully relativistic approach to be applied to parity-violating (PV) quasielastic $(\vec{e},e^{\prime }N)$ processes. This is of importance as a preliminary step in the subsequent study of inclusive quasielastic PV $(\vec{e},e^{\prime })$ reactions. Moreover, our present analysis allows us to disentangle effects associated with the off-shell character of nucleons in nuclei, gauge ambiguities, and the role played by the lower components in the nucleon wave functions, i.e., dynamical relativistic effects. This study can help in getting clear information on PV effects. Particular attention is paid to the relativistic plane-wave impulse approximation where the explicit expressions for the PV single-nucleon responses are shown for the first time.

Penning trap mass measurements of neutron-deficient Rb isotopes have been performed at TRIUMF's Ion Trap for Atomic and Nuclear Science (TITAN) facility by utilizing highly charged ions (HCIs). As imperative for a new approach with significant gain in measurement precision, experimental procedures, and systematic uncertainties are discussed in detail. Among the investigated nuclides, the superallowed nuclear $\beta$ emitter ${}^{74}\mathrm{Rb}$ will especially benefit from the advantage offered by HCI because the limited attainable precision owing to its short half-life $(T_{1/2}=65$ ms) represents a challenge for conventional Penning trap mass spectrometry. Motivated by an updated $Q_{\mathrm{EC}}$ value for ${}^{74}\mathrm{Rb}$ of 10 416.8(3.9) keV and its large isospin-symmetry breaking corrections, we present a new test to benchmark the consistency between theoretical models of isospin-symmetry breaking corrections in superallowed decays, the conserved vector current hypothesis, and experimental data.

A realistic shell-model study is performed for neutron-deficient tin isotopes up to mass $A=108$. All shell-model ingredients, namely, two-body matrix elements, single-particle energies, and effective charges for electric quadrupole transition operators, have been calculated by way of the many-body perturbation theory, starting from a low-momentum interaction derived from the high-precision CD-Bonn free nucleon-nucleon potential. The focus has been on the enhanced quadrupole collectivity of these nuclei, which is testified by the observed large $B(E2;0_1^{+}\to 2_1^{+})\mathrm{s}$. Our results give evidence of the crucial role played by the $Z=50$ cross-shell excitations that need to be taken into account explicitly to obtain a satisfactory theoretical description of light tin isotopes. We find also that a relevant contribution comes from the calculated neutron effective charges, whose magnitudes exceed the standard empirical values. An original double-step procedure has been introduced to reduce effectively the model space in order to overcome the computational problem.

Based on the semiclassical extended Thomas-Fermi approach, we study the mass dependence of the symmetry energy coefficients of finite nuclei for 36 different Skyrme forces. The reference densities of both light and heavy nuclei are obtained. Eight models based on the nuclear liquid drop concept and the Skyrme force SkM* suggest the symmetry energy coefficient $a_{\mathrm{sym}}=22.90\pm 0.15$ MeV at $A=260$, and the corresponding reference density is ${\rho }_A\simeq 0.1{\mathrm{fm}}^{-3}$ at this mass region. The standard Skyrme energy density functionals give negative values for the coefficient of the $I^4$ term in the binding energy formula, whereas the latest Weizsäcker-Skyrme formula and the experimental data suggest positive values for the coefficient.

The study of transport coefficients of strongly interacting matter gained impetus after the discovery of the best fluid ever created in ultrarelativistic heavy-ion collision experiments. In this article, we have calculated one such coefficient, viz., electrical conductivity of the quark gluon plasma (QGP) phase, which exhibits an anisotropy in the momentum space. The relativistic Boltzmann's kinetic equation has been solved in the relaxation-time approximation to obtain the electrical conductivity. We have used the quasiparticle description to define the basic properties of QGP through the distribution functions of partons. We have compared our results with the corresponding results obtained in lattice as well as other model calculations. Further, we extend our model to calculate the electrical conductivity at finite chemical potential.