The momentum dependence of the drag coefficient of heavy quarks propagating through a quark gluon plasma (QGP) has been evaluated. The results have been used to estimate the nuclear suppression factor of charm and bottom quarks in a QGP. We observe that the momentum dependence of the transport coefficients plays crucial role in the suppression of the heavy quarks and, consequently, in discerning the properties of the QGP using heavy flavors as a probe. We show that the large suppression of the heavy quarks observed at the BNL Relativistic Heavy Ion Collider (RHIC) and at the CERN Large Hadron Collider (LHC) is predominantly due to the radiative losses. The suppression of $D^0$ in $\text{Pb}+\text{Pb}$ collisions at LHC energies—recently measured by the ALICE Collaboration—has also been studied.

We study the validity of pair approximations of the nuclear shell model (SM) for a few realistic nuclei (${}^{130-131}$Te and ${}^{132}$I here) in open shells (i.e., nuclei with both valence protons and valence neutrons). We take a phenomenological shell model Hamiltonian, which includes the single-particle energy term, monopole and quadrupole pairing interactions for like particles, and quadrupole-quadrupole interactions between all valence nucleons. We make comparisons of energy levels and $B\left(E2\right)$ values calculated by pair approximations with those in the SM calculations. The overlaps between wave functions of the nucleon pair approximation (NPA) and those of the SM are presented explicitly for the low-lying states. Our calculated results demonstrate that the NPA is a remarkable approximation of the SM for these nuclei. The important role played by pairs with negative parity in some low-lying states is discussed.

We have measured the cross section of the photoneutron reaction channel ${}^7\text{Li}+\gamma {\to }^6\text{Li(g.s.)}+n$ where the progeny nucleus is the ground state of ${}^6$Li. We obtained the absolute cross section at photon energies 10, 11, 12, 13, 15, 20, 25, 30, and 35 MeV and also the dependence of the cross section on polar angle for all but the highest photon energy. For the energies 10 to 15 MeV we were able to use linearly polarized photons to obtain the dependence of the cross section on the photon polarization.

The existence of rotating quasimolecular hyperdeformed states formed in the entrance channel of capture reactions of light nuclei is predicted within a rotational liquid-drop model, including the nuclear proximity energy. The $l$-dependent capture barrier heights and positions, as well as the angular momentum, the energy, and the moment of inertia ranges of these very deformed high-spin states, are given for the reactions ${}^{13}$C + ${}^{13}$C, ${}^{16}$O + ${}^{16}$O, ${}^{28}$Si + ${}^{12}$C, ${}^{28}$Si + ${}^{16}$O, ${}^{24}$Mg + ${}^{24}$Mg, ${}^{28}$Si + ${}^{24}$Mg, ${}^{28}$Si + ${}^{28}$Si, ${}^{28}$Si + ${}^{40}$Ca, ${}^{40}$Ca + ${}^{40}$Ca, ${}^{40}$Ca + ${}^{48}$Ca, ${}^{48}$Ca + ${}^{48}$Ca, and ${}^{58}$Ni + ${}^{58}$Ni. Analytical formulas are provided for any reaction between light nuclei.

We address the issue of consistent interactions for off-shell fermion fields of arbitrary spin. These interactions play a crucial role in the quantum hadrodynamical description of high-spin baryon resonances in hadronic processes. The Rarita-Schwinger (R-S) description of high-spin fermion fields involves unphysical degrees of freedom associated with their lower-spin content. These enter the interaction if not eliminated outright. The invariance condition of the interaction under the unconstrained R-S gauge removes the lower-spin content of the fermion propagator and leads to a consistent description of the interaction. We develop the most general consistent interaction structure for high-spin fermions. We find that the power of the momentum dependence of a consistent interaction rises with the spin of the fermion field. This leads to unphysical structures in the energy dependence of the computed tree-level cross sections when the short-distance physics is cut off with standard hadronic form factors. A spin-dependent hadronic form factor is proposed that suppresses the unphysical artifacts.

This paper describes measurements on the isotopes ${}^{75,77,78}$Cu by the technique of in-source laser spectroscopy, at the ISOLDE facility, CERN. The role of this technique is briefly discussed in the context of this and other, higher resolution, methods applied to copper isotopes in the range ${}^{57-78}$Cu. The data, analyzed in comparison with previous results on the lighter isotopes ${}^{59,63}$Cu, establish the ground-state nuclear spin of ${}^{75,77}$Cu as 5/2 and yield their magnetic dipole moments as +1.01(5)${\mu }_N$ and +1.61(5)${\mu }_N$, respectively. The results on ${}^{78}$Cu show no evidence for long-lived isomerism at this mass number and are consistent with a spin in the range 3–6 and moment of 0.0(4) ${\mu }_N$.

By using recent fusion cross section measurements for the system ${}^8$B + ${}^{58}$Ni, a simultaneous analysis of elastic scattering, fusion, and total reaction cross sections is performed for the weakly bound system ${}^8$B + ${}^{58}$Ni at energies close to the Coulomb barrier. The analysis is carried out with an optical potential with fusion and direct reaction parts (i.e., the nuclear polarization potential $U$ is split into a volume part $U_F$, which accounts for fusion reactions and a surface part $U_{\mathrm{DR}}$, responsible for direct reactions). The parameters of the Woods-Saxon potentials are determined by a ${\chi }^2$ analysis of the data. The presence of the threshold anomaly is investigated from the energy dependence of both the fusion and direct reaction parts of the polarization potential.

Nucleon self-energies for ${}^{40,48,60}$Ca isotopes are generated with the microscopic Faddeev-random-phase approximation (FRPA). These self-energies are compared with potentials from the dispersive optical model (DOM) that were obtained from fitting elastic-scattering and bound-state data for ${}^{40,48}$Ca. The ab initio FRPA is capable of explaining many features of the empirical DOM potentials including their nucleon asymmetry dependence. The comparison furthermore provides several suggestions to improve the functional form of the DOM potentials, including among others the exploration of parity and angular momentum dependence. The nonlocality of the FRPA imaginary self-energy, illustrated by a substantial orbital angular momentum dependence, suggests that future DOM fits should consider this feature explicitly. The roles of the nucleon-nucleon tensor force and charge-exchange component in generating the asymmetry dependence of the FRPA self-energies are explored. The global features of the FRPA self-energies are not strongly dependent on the choice of realistic nucleon-nucleon interactions.

The stochastic Langevin model is employed to study dissipation properties in fission in the ${}^{16}$O $+$ ${}^{181}$Ta $\to$${}^{197}$Tl system by analyzing prescission neutron yields measured in this reaction. It has been found that the ${}^{197}$Tl nuclei undergo fission that is not in accordance with the standard Bohr-Wheeler statistical theory. A detailed comparison with previously published work in which fission excitation functions measured in ${}^{3,4}$He $+$ ${}^{197}$Au $\to$${}^{200,201}$Tl are shown to be in excellent agreement with the fission width formula predicted by the traditional models of nuclear fission suggests that nuclear dissipation strength may have an angular momentum dependence in addition to the known deformation and temperature dependence. Implications for the basic understanding of the observed abnormal rise in prescission particles at high energy and the need for further experimental confirmations are discussed.

In this work we fit $neutron$-${}^{12}C$ elastic scattering angular distributions in the energy range 12 to 20 MeV, by adding a velocity-dependent term to the optical potential. This term introduces a wave function gradient, whose coefficient is real and position-dependent, and which represents a nonlocality. We pay special attention to the prominent backscattering minima, which depend sensitively on the incident energies and which are a tell-tale of nonlocalities. Reasonable fits to the analyzing power data are also obtained as a by-product. All our potentials have the form of conventional Woods-Saxon shapes or their derivatives. The number of our parameters (12) is smaller than the number for other local optical potentials, and they vary monotically with energy, while the strengths of the real and imaginary parts of the central potential are nearly constants. Our nonlocality is in contrast to other forms of nonlocalities introduced previously.

Experimental details of a virtual Compton scattering (VCS) experiment performed on the proton at the MIT-Bates out-of-plane scattering facility are presented. The VCS response functions $P_{LL}-P_{TT}/\phantom{P_{TT}\varepsilon }\varepsilon$ and $P_{LT}$ have been measured at $Q^2=0.057{\mathrm{GeV}}^2/c^2$. The generalized electric and magnetic polarizabilities, $\alpha \left(Q^2\right)$ and $\beta \left(Q^2\right)$, and the mean-square electric polarizability radius$\langle r_{\alpha }^2\rangle$ are obtained from a dispersion analysis of the data. The results are in good agreement with $O\left(p^3\right)$ heavy baryon chiral perturbation and indicate the dominance of mesonic effects in the polarizabilities.

We study the electromagnetic responses of ${}^4$He within the framework of the self-consistent continuum random-phase approximation theory. In this approach, the ground-state properties are described by a Hartree-Fock calculation. The single-particle basis constructed in this manner is used in the calculations of the continuum responses of the system. Finite-range interactions are considered in the calculations. We compare our results with photon-absorption cross sections and electron-scattering quasielastic data. From this comparison, and also from the comparison with the results of microscopic calculations, we deduce that our approach describes well the continuum excitation.

We study the correlation between balance energy and transition energy of fragments in heavy-ion collisions for different systems at incident energies between 40 and 1200 MeV/nucleon using an isospin-dependent quantum molecular dynamics model. With increasing incident energy, the elliptic flow shows a transition from positive (in-plane) to negative (out-of-plane) flow. This transition energy is found to depend on the size of the fragments, composite mass of the reacting system, and the impact parameter of the reaction. It has been observed that a reduced cross section can explain the experimental data. There is a correlation between transition energy and balance energy as their difference decreases with an increase in the total mass of colliding nuclei.

An approach we have proposed recently for calculation of $Q_{\alpha }$ energy and decay half-life $T_{1/2}^{\alpha }$ on the $\alpha$ decay of radioactive heavy ions is applied to the evaluation of these two important parameters for the nuclei in the superheavy region $Z$ $=$ 112–118 for which experimental data are not available. It is shown that the $\alpha$ $+$ nucleus potential represented by an exactly solvable potential used in the calculation could be expressed in terms of proton ($Z$) and neutron ($N$) numbers of the $\alpha$ emitter so that varieties of $\alpha$-emitting nuclei differing in their $Z$ and $N$ values could be addressed for their decay properties without the help of any adjustable parameter and the results of $Q_{\alpha }$ and $T_{1/2}^{\alpha }$ for a nucleus are estimated without any prior knowledge of any one of these quantities. This procedure to obtain the values of $Q_{\alpha }$ and $T_{1/2}^{\alpha }$ works well to reproduce the known experimental results for superheavy nuclei and hence, the procedure is expected to provide proper information about these parameters in experiments on $\alpha$ decay of new nuclei in the superheavy region.

The conventional perception is that the amplitudes of Delbrück scattering calculated to all orders in the charge number $Z$ of the target nucleus should exhibit a scaling behavior at high energies. To examine this hypothesis the available experimental data of differential cross sections of elastic scattering in the energy range between 140 MeV and $7.11$ GeV are analyzed. It is found that the experimental data do not show scaling characteristics. Such a finding, though apparently against the standard notion, is not unexpected because at high energies Delbrück scattering is in very forward direction and the theoretical arguments demand that to observe scaling, not only the energy itself but the product of scattering angles and energy also should be very large.

The core of neutron-star matter is supposed to be at a much higher density than the normal nuclear-matter density, for which various possibilities have been suggested, such as, for example, meson or hyperon condensation and/or deconfined quark or color-superconducting matter. In this work, we explore the implication on hadron physics of a dense compact object that has three “phases”: nuclear matter at the outer layer, kaon condensed nuclear matter in the middle, and strange quark matter at the core. Using a drastically simplified but not unreasonable model, we develop the scenario where the different phases are smoothly connected with the kaon condensed matter playing a role of a “doorway” to a quark core, the equation of state of which with parameters restricted within the range allowed by nature could be made compatible with the mass vs radius constraint given by the 1.97-solar-mass object PSR J1614-2230 recently observed.

Random walks on five-dimensional potential-energy surfaces were recently found to yield fission-fragment mass distributions that are in remarkable agreement with experimental data. Within the framework of the Smoluchowski equation of motion, which is appropriate for highly dissipative evolutions, we discuss the physical justification for that treatment and investigate the sensitivity of the resulting mass yields to a variety of model ingredients, including in particular the dimensionality and discretization of the shape space and the structure of the dissipation tensor. The mass yields are found to be relatively robust, suggesting that the simple random walk presents a useful calculational tool. Quantitatively refined results can be obtained by including physically plausible forms of the dissipation, which amounts to simulating the Brownian shape motion in an anisotropic medium.

The first results from heavy ion collisions at the Large Hadron Collider for charged-particle spectra and elliptic flow are compared to an event-by-event hybrid approach with an ideal hydrodynamic expansion. This approach has been shown to successfully describe bulk observables at the BNL Relativistic Heavy Ion Collider. Without changing any parameters of the calculation, the same approach is applied to Pb + Pb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$. This is an important test if the established understanding of the dynamics of relativistic heavy ion collisions is also applicable at even higher energies. Specifically, we employ the hybrid approach with two different equations of state and the pure hadronic transport approach to indicate sensitivities to finite viscosity. The centrality dependence of the charged hadron multiplicity, $p_T$ spectra, and differential elliptic flow are shown to be in reasonable agreement with the ALICE Collaboration data. Furthermore, we make predictions for the transverse mass spectra of identified particles and triangular flow. The eccentricities and their fluctuations are found to be surprisingly similar to the ones at lower energies, and therefore, the triangular flow results are very similar. Any deviations from these predictions will indicate the need for different physics mechanisms responsible for the dynamics of heavy ion collisions.