The generalized parton distribution $H$ and $E$ of the ${}^3$He nucleus, which can be measured in hard exclusive processes such as coherent deeply virtual Compton scattering, are thoroughly analyzed in impulse approximation, within the Av18 interaction. It is found that their sum, at low momentum transfer, is dominated to a large extent by the neutron contribution: the peculiar spin structure of ${}^3$He makes this target unique for the extraction of the neutron information. This observation allows access, in dedicated experiments, to the orbital angular momentum of the partons in the neutron.

The nuclear level density and the $\gamma$-ray strength function have been determined for ${}^{43}\mathrm{Sc}$ in the energy range up to 2 MeV below the neutron separation energy using the Oslo method with the $46\mathrm{Ti}$$(p,\alpha )$${}^{43}\mathrm{Sc}$ reaction. A comparison to ${}^{45}\mathrm{Sc}$ shows that the level density of ${}^{43}\mathrm{Sc}$ is smaller by an approximately constant factor of two. This behavior is well reproduced in a microscopic, combinatorial model calculation. The $\gamma$-ray strength function increases at low $\gamma$-ray energies, a feature which has been observed in several nuclei but which still awaits theoretical explanation.

Neutron shell structure and the resulting possible deformation in the neighborhood of neutron-drip-line nuclei are systematically discussed, based on both bound and resonant neutron one-particle energies obtained from spherical and deformed Woods-Saxon potentials. Owing to the unique behavior of weakly bound and resonant neutron one-particle levels with smaller orbital angular momenta $\ell$, a systematic change in the shell structure and thereby a change in the neutron magic numbers are pointed out, compared with those of stable nuclei expected from the conventional j-j shell model. For a spherical shape with the operator of the spin-orbit potential conventionally used, the ${\ell }_j$ levels belonging to a given oscillator major shell with parallel spin and orbital angular momenta tend to gather together in the energetically lower half of the major shell, while the levels with antiparallel spin and orbital angular momenta gather in the upper half. This tendency leads to a unique shell structure and possible deformation when neutrons start to occupy the orbits in the lower half of the major shell. Among others, the neutron magic number $N=28$ disappears and $N=50$ may disappear, while the magic number $N=82$ may presumably survive owing to the large $\ell =5$ spin-orbit splitting for the $1h_{11/2}$ orbit. On the other hand, an appreciable amount of energy gap may appear at $N=16$ and 40 for spherical shape, while neutron-drip-line nuclei in the region of neutron numbers above $N=20$, 40, and 82, namely, $N\approx 21$–28, $N\approx 41$–54, and $N\approx 83$–90, may be quadrupole deformed, although the possible deformation also depends on the proton number of the respective nuclei.

Particle production in Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV is studied in the $(3+1)$-dimensional viscous hydrodynamic model. The shapes of the calculated transverse momentum spectra of ${\pi }^{+}$, $K^{+}$, protons, ${\Xi }^{-}$, and ${\Omega }^{-}$ are in satisfactory agreement with preliminary data of the ALICE Collaboration, while the particle ratio $p/{\pi }^{+}$ is slightly overpredicted, and the strange baryon yields are underpredicted.

We use the nonstatistical fluctuation to explore the higher-moment singularities of net-proton event distributions in the relativistic $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}$ from 11.5 to 200 GeV calculated by the parton and hadron cascade model PACIAE. The PACIAE results of mean ($M$), variance (${\sigma }^2$), skewness ($S$), and kurtosis ($\kappa$) are consistent with the corresponding STAR data. Nonstatistical moments are calculated as the difference between the moments derived from real events and the ones from mixed events, which are constructed by combining particles randomly selected from different real events. An evidence of singularity at $\sqrt{s_{NN}}\sim$ 60 GeV is first seen in the energy-dependent nonstatistical $S$ and $S\sigma$.

We evaluate the shear viscosity of a pion gas in the relativistic kinetic theory approach. The in-medium propagator of the $\rho$ meson at finite temperature is used to evaluate the $\pi \pi$ scattering amplitude in the medium. The real and imaginary parts of the self-energy calculated from one-loop diagrams are seen to have noticeable effects on the scattering cross section. The consequences on the temperature dependence of the shear viscosity evaluated in the Chapman-Enskog and relaxation-time approximations are studied.

Background The main energy production mechanism for massive stars during hydrogen burning is the CNO cycle. The reactions ${}^{15}$N${(p,\gamma )}^{16}$O and ${}^{15}$N${(p,{\alpha }_0)}^{12}$C form a branch point in this cycle. The ratio of the corresponding reaction rates determines the CNO abundances evolving during this early stage of the star's life which affects the subsequent nucleosynthesis in later phases of stellar evolution. Determining the cross sections for these reactions at stellar energies is often very difficult. Measurements of other reactions that populate the same compound nucleus can often be used to indirectly determine the cross section of interest.

Purpose The nuclear level properties of broad resonances in ${}^{16}$O which characterize the cross section of the reactions ${}^{15}$N${(p,\gamma )}^{16}$O and ${}^{15}$N${(p,{\alpha }_0)}^{12}$C must be well known in order to accurately extrapolate the measured cross sections to the stellar energy range. The $R$-matrix formalism is a powerful technique for interpreting these cross sections and is greatly enhanced by additional data in other reaction channels. In a previous publication, measurements were reported for the cross section of the reaction ${}^{15}$N${(p,\gamma )}^{16}$O for the ground state transition only. Concurrently, $\gamma$-ray measurements were recorded for the cascade transitions to the $E_x$ $=$ 6.050, 6.130, and 7.117 MeV bound states of ${}^{16}$O as well as from the reaction ${}^{15}$N${(p,{\alpha }_1\gamma )}^{12}$C. Excitation curves for the cascade transitions have never been measured and the excitation curve data for the ${}^{15}$N${(p,{\alpha }_1\gamma )}^{12}$C reaction found in the literature may suffer from substantial errors due to target contamination.

Methods Angle integrated cross sections are measured over the proton energy range from $E_p$ $=$ 0.14 to 1.80 MeV for the $\gamma$-ray cascade transitions and for the reaction ${}^{15}$N${(p,{\alpha }_1\gamma )}^{12}$C.

Results De-excitations associated with several compound nucleus states in ${}^{16}$O are observed in both the $\gamma$-ray and ${\alpha }_1$ channels. An $R$-matrix analysis is performed and partial decay widths are deduced for several previously unobserved decay branchings from these states.

Conclusion For the first time, excitation curves for the cascade transitions to the ${}^{16}$O bound states at $E_x$ $=$ 6.050, 6.130, and 7.117 MeV are reported over the energy range from $E_p$ $=$ 0.14 to 1.80 MeV. In addition, an improved measurement of the ${}^{15}$N${(p,{\alpha }_1\gamma )}^{12}$C excitation curve has been made over a similar energy range.

The scintillation light yield of liquid argon from nuclear recoils relative to electronic recoils has been measured as a function of recoil energy from 10 keVr up to 250 keVr at zero electric field. The scintillation efficiency, defined as the ratio of the nuclear recoil scintillation response to the electronic recoil response, is $0.25\pm 0.01+0.01$ (correlated) above 20 keVr.

In this work, we expand upon our previous study, the effect of hot nuclear matter on the calculation of the internuclear potential [Phys. Rev. C 84, 024612 (2011)], to the ${}^{28}\mathrm{Si}+{}^{40}\mathrm{Ca}$, ${}^{35}\mathrm{Cl}+{}^{48}\mathrm{Ti}$, and ${}^{40}\mathrm{Ar}+{}^{74}\mathrm{Ge}$ collision systems. For this purpose, we have employed the equation of state of hot nuclear matter, which is based on density-dependent Seyler-Blanchard formalism at finite temperature, to discuss the energy dependence of a repulsive core potential in the nucleon-nucleon interaction. The obtained values for strength of this potential show a linear dependence as a function of excitation energy $E^{*}$ (or temperature $T$) of the compound nucleus. Indeed, it is predictable that the effect of hot nuclear matter on heavy-ion reactions can be formulated by an additional energy-dependent function in the nucleon-nucleon potential.

We present a nonperturbative derivation of effective valence-shell Hamiltonians in the framework of the re-cently developed in-medium similarity renormalization group (IM-SRG). As a first application, we calculate the spectra of $p$- and $sd$-shell nuclei, ${}^6$Li and ${}^{18}$O, based on evolved chiral nucleon-nucleon interactions. For ${}^6$Li, the spectrum is in very good agreement with ab initio results. For ${}^{18}$O, the IM-SRG provides a new method for the shell model to systematically go beyond effective interaction techniques based on diagrammatic expansions.

The deuterium-tritium (D-T) γ-to-neutron branching ratio [${}^3$H($d$,γ)${}^5$He/${}^3$H(d,n)${}^4$He] was determined under inertial confinement fusion (ICF) conditions, where the center-of-mass energy of 14–24 keV is lower than that in previous accelerator-based experiments. A D-T branching ratio value of (4.2 ± 2.0) × 10${}^{-5}$ was determined by averaging the results of two methods: (1) a direct measurement of ICF D-T γ-ray and neutron emissions using absolutely calibrated detectors, and (2) a separate cross-calibration against the D-${}^3$He γ-to-proton branching ratio [${}^3$He($d$,γ)${}^5$Li/${}^3$He(d,p)${}^4$He]. Neutron-induced backgrounds were significantly reduced as compared to traditional beam-target accelerator-based experiments due to the short pulse nature of ICF implosions and the use of gas Cherenkov γ-ray detectors with fast temporal responses and inherent energy thresholds. These measurements of the D-T branching ratio in an ICF environment test several theoretical assumptions about the nature of $A$ = 5 systems, including the dominance of the 3/2${}^{+}$ resonance at low energies, the presence of the broad first excited state of ${}^5$He in the spectra, and the charge-symmetric nature of the capture processes in the mirror systems ${}^5$He and ${}^5$Li.

We investigate how strongly a hypothetical ${}^1{S}_0$ bound state of two neutrons would affect observables in neutron-deuteron reactions. To that aim we extend our momentum-space scheme of solving the three-nucleon Faddeev equations and incorporate in addition to the deuteron also a ${}^1{S}_0$ di-neutron bound state. We discuss effects induced by a di-neutron on the angular distributions of the neutron-deuteron elastic scattering and deuteron breakup cross sections. A comparison to the available data for the neutron-deuteron total cross section and elastic scattering angular distributions cannot decisively exclude the possibility that two neutrons can form a ${}^1{S}_0$ bound state. However, strong modifications of the final-state-interaction peaks in the neutron-deuteron breakup reaction seem to disallow the existence of a di-neutron.

We suggest a perturbation method for obtaining the lowest eigenvalues of the nuclear-shell -model Hamiltonian. We introduce a “cutoff” based on the features of the nuclear-shell-model Hamiltonian matrices. Our new method is exemplified by a few realistic nuclei. Overlaps between the wave functions of our approach and those of the exact shell model are presented. Some of electromagnetic quantities are also discussed.

The ground state of a general pairing Hamiltonian for a finite nuclear system is constructed as a product of collective, real, distinct pairs. These are determined sequentially via an iterative variational procedure that resorts to diagonalizations of the Hamiltonian in restricted model spaces. Different applications of the method are provided that include comparisons with exact and projected BCS results. The quantities that are examined are correlation energies, occupation numbers, and pair transfer matrix elements. In a first application within the picket-fence model, the method is seen to generate the exact ground state for pairing strengths confined in a given range. Further applications of the method concern pairing in spherically symmetric mean fields and include simple exactly solvable models as well as some realistic calculations for middle-shell Sn isotopes. In the latter applications, two different ways of defining the pairs are examined: either with $J=0$ or with no well defined angular momentum. The second choice is revealed to be more effective, leading, under some circumstances, to solutions that are basically exact.

The structure of neutron rich even-even ${}^{150-164}$Sm nuclei is investigated in the framework of deformed Hartree-Fock, Skyrme Hartree-Fock $+$ BCS, and relativistic mean-field formalisms. We analyze the bulk as well as the microscopic properties of these nuclei to investigate the proposed “island of stability” near the neutron drip line for $N=100,Z\approx 62$.

In order to disentangle the contribution of complete and incomplete fusion components and to study their dependence on various entrance-channel observables, the measurement and analysis of forward recoil ranges, which is the direct measure of linear momentum transfer from projectile to the target nuclei, has been done in the interaction of ${}^{12}$C beam with ${}^{159}$Tb target nucleus at three distinct above-barrier energies $\approx 74$, 80, and 87 MeV. The recoil-catcher technique followed by off-line $\gamma$-ray spectroscopy has been used. The complete and incomplete fusion events have been tagged by full and partial linear momentum transfer components, respectively. The observed incomplete fusion events have been explained on the basis of the breakup fusion model where these events may be attributed to the fusion of ${}^8$Be and/or ${}^4$He from ${}^{12}$C projectile to the target nucleus. Analysis of the data indicates that the incomplete fusion has significant contribution at the studied energies and its contribution has been found to increase with the beam energy. An attempt has also been made to understand the projectile structure effect on the underlying reaction dynamics.

Measurements of the density dependence of the symmetry free energy in low-density clustered matter have been extended using the Neutron Ion Multidetector for Reaction Oriented Dynamics at Texas A&M University. Thermal coalescence models were employed to extract densities $\rho$ and temperatures $T$ for evolving systems formed in collisions of 47$A$ MeV ${}^{40}$Ar+${}^{112}$Sn,${}^{124}$Sn and ${}^{64}$Zn+${}^{112}$Sn, ${}^{124}$Sn. Densities of $0.03⩽\rho /{\rho }_0⩽0.2$ and temperatures in the range 5–10 MeV have been sampled. The symmetry free energy coefficients are found to be in good agreement with values calculated using a quantum statistical model. Values of the corresponding symmetry free energy coefficient are derived from the data using entropies derived from the model.

A four-dimensional dynamical model based on Langevin equations was developed and applied to calculate a wide set of experimental observables for the reactions ${}^{16}\mathrm{O}+{}^{208}\mathrm{Pb}\to {}^{224}\mathrm{Th}$ and ${}^{16}\mathrm{O}+{}^{232}\mathrm{Th}\to {}^{248}\mathrm{Cf}$ over a wide range of excitation energy. The fusion-fission and evaporation residue cross sections, fission fragment mass-energy distribution parameters, prescission neutron multiplicities, and anisotropy of angular distribution of fission fragments could be reasonably reproduced using a modified one-body mechanism for nuclear friction with a reduction coefficient of the contribution from a wall formula $k_s\simeq 0.25$ and a dissipation coefficient for the orientation degree of freedom ($K$ coordinate) ${\gamma }_K\simeq$ 0.077 ${\left(\mathrm{MeV}\mathrm{zs}\right)}^{-1/2}$. Inclusion of the $K$ coordinate into calculation of potential energy changes the stiffness of the nucleus with respect to mass asymmetry coordinate for the values of $K\ne 0$ and results in a shift of the Businaro-Gallone point towards larger $Z^2/A$ values. The experimental data on the fission fragment mass-energy distribution parameters together with mean prescission neutron multiplicity for heavy fissioning nuclei are reproduced through the four-dimensional Langevin calculations more accurately than through three-dimensional calculations.

Measurements of the anisotropy parameter $v_2$ of identified hadrons (pions, kaons, and protons) as a function of centrality, transverse momentum $p_T$, and transverse kinetic energy KE${}_T$ at midrapidity ($\left|\eta \right|<0.35$) in Au + Au collisions at $\sqrt{s_{NN}}=200$ GeV are presented. Pions and protons are identified up to $p_T=$ 6 GeV$/c$, and kaons up to $p_T=$ 4 GeV$/c$, by combining information from time-of-flight and aerogel Čerenkov detectors in the PHENIX Experiment. The scaling of $v_2$ with the number of valence quarks ($n_q$) has been studied in different centrality bins as a function of transverse momentum and transverse kinetic energy. A deviation from previously observed quark-number scaling is observed at large values of KE${}_T/n_q$ in noncentral Au + Au collisions ($20–60\%$), but this scaling remains valid in central collisions ($0–10\%$).

The ${}^{22}$Ne($\alpha$,$n$)${}^{25}$Mg reaction is an important source of neutrons for the $s$-process. In massive stars responsible for the weak component of the $s$-process, ${}^{22}$Ne($\alpha$,$n$)${}^{25}$Mg is the dominant source of neutrons, both during core helium burning and in carbon-shell burning. For the main $s$-process component produced in asymptotic giant branch (AGB) stars, the ${}^{13}$C($\alpha$,$n$)${}^{16}$O reaction is the dominant source of neutrons operating during the interpulse period, with the ${}^{22}$Ne$+\alpha$ source affecting mainly the $s$-process branchings during a thermal pulse. Rate uncertainties in the competing ${}^{22}$Ne($\alpha$,$n$)${}^{25}$Mg and ${}^{22}$Ne($\alpha$,$\gamma$)${}^{26}$Mg reactions result in large variations of $s$-process nucleosynthesis. Here, we present up-to-date and statistically rigorous ${}^{22}$Ne$+\alpha$ reaction rates using recent experimental results and Monte Carlo sampling. Our new rates are used in postprocessing nucleosynthesis calculations both for massive stars and AGB stars. We demonstrate that the nucleosynthesis uncertainties arising from the new rates are dramatically reduced in comparison to previously published results, but several ambiguities in the present data must still be addressed. Recommendations for further study to resolve these issues are provided.