Photons, as well as quarks and gluons, are constituents of the infinite momentum frame (IMF) wave function of an energetic particle. They are mostly equivalent photons whose amplitude follows from the Lorentz transformation of the particle rest frame Coulomb field into the IMF and from the conservation of the electromagnetic current. We evaluate in a model independent way the dominant photon contribution $\propto {\alpha }_{\mathrm{em}}(Z^2/A^{4/3})\ln (1/R_A{m}_{N}x)$ to the nuclear structure functions as well as the term $\propto {\alpha }_{\mathrm{em}}Z/A$. In addition we show that the definition of $x$ consistent with the exact kinematics of $\mathit{eA}$ scattering (with exact sum rules) works in the same direction as the nucleus field of equivalent photons. Combined, these effects account for the bulk of the hadronic European Muon Collaboration (EMC) effect for $x⩽0.5$ where Fermi motion effects are small. In particular, for these $x$ the hadronic mechanism contribution to the EMC effect does not exceed $~3\%$ for all nuclei. Also, the $A$ dependence of the hadronic mechanism of the EMC effect for $x>0.5$ is significantly modified.

The lowest six rotational bands have been studied in the particle-rotor model with the particle-hole configuration $\pi h_{11/2}^1\otimes \nu h_{11/2}^{-1}$ and different values of the triaxiality parameter $\gamma$. Both constant and spin-dependent variable moments of inertia (CMI and VMI, respectively) are introduced. The energy spectra, electromagnetic transition probabilities, angular momentum components, and $K$ distribution are examined. It is shown that, besides bands $1$ and $2$, the predicted bands $3$ and $4$ in the calculations with both CMI and VMI for atomic nuclei with $\gamma ={30}^{°}$ could be interpreted as chiral doublet bands.

Radiative decays $\pi {}^0({\pi {}^0}^{\prime })\to \gamma +\gamma$, ${\pi {}^0}^{\prime }\to \rho {}^0(\omega )+\gamma$, ${\rho {}^0}^{\prime }(\omega {}^{\prime })\to \pi {}^0+\gamma$, and ${\rho {}^0}^{\prime }(\omega {}^{\prime })\to {\pi {}^0}^{\prime }+\gamma$ are considered in the framework of the $\mathrm{SU}(2)\times \mathrm{SU}(2)$ Nambu–Jona-Lasinio (NJL) model. Radially excited mesons are described with the help of a simple polynomial form factor. In spite of mixing of the ground and excited meson states in this model, the decay widths of $\pi {}^0\to \gamma +\gamma$ and $\rho {}^0(\omega )\to \pi {}^0+\gamma$ are found to be in good agreement with experimental data, as in the standard NJL model. Our predictions for decay widths of radially excited mesons can be verified in future experiments.

Two of the four known rotational bands in ${}^{75}\mathrm{Rb}$ were studied via the ${}^{40}\mathrm{Ca}({}^{40}\mathrm{Ca},\alpha \mathrm{p}){}^{75}\mathrm{Rb}$ reaction at a beam energy of 165 MeV. Transitions were observed up to the maximum spin $I_{\max }$ of the assigned configuration in one case and one-transition short of $I_{\max }$ in the other. Lifetimes were determined using the residual Doppler shift attenuation method. The deduced transition quadrupole moments show a small decrease with increasing spin, but remain large at the highest spins. The results obtained are in good agreement with cranked Nilsson-Strutinsky calculations, which indicate that these rotational bands do not terminate, but remain collective at $I_{\max }$.

The symmetry energy coefficients for nuclei with mass number $A=20$–$250$ are extracted from more than $2000$ measured nuclear masses. With the semiempirical connection between the symmetry energy coefficients of finite nuclei and the nuclear symmetry energy at reference densities, we investigate the density dependence of the symmetry energy of nuclear matter at subnormal densities. The obtained results are compared with those extracted from other methods.

We discuss calculations of the single-particle states in magic nuclei, performed within the particle-vibration coupling (PVC) approach by using consistently the Skyrme effective interaction. The vibrations are calculated within fully self-consistent random-phase approximation and the whole interaction is also used in the PVC vertex. Our main emphasis is therefore the discussion of our results in comparison with those in which some approximation is made. The perspectives for improving current density functional theory (DFT) calculations are also addressed.

Excited levels in the ${}^{109}\mathrm{Tc}$ nucleus, populated in the spontaneous fission of ${}^{248}\mathrm{Cm}$, have been studied using the EUROGAM2 array. In ${}^{109}\mathrm{Tc}$ we have found a new band corresponding to the $\pi 5$/$2^{-}$[303] configuration and a three-quasiparticle band with $I^{\pi }=(15/2^{-})$ band-head level at 1749.5 keV. The structure of the 1749.5-keV level probably involves the $\{\pi 5/2^{+}[422]\nu (5/2^{-}[532],5/2^{+}[413])\}{}_{{15/2}^{-}}$ prolate configuration. The quasiparticle-rotor model calculations performed in this work show that the odd-proton configurations observed in ${}^{107}\mathrm{Tc}$ and ${}^{109}\mathrm{Tc}$ are consistent with the scheme of proton excitations in a prolate triaxial potential. Significant differences between the degree of triaxiality observed for positive- and negative-parity excitations may be due to blocking of the triaxial shape by the odd proton populating negative-parity orbitals. The properties of the new $494.5-$, $1440.7-$, and $1748.8$-keV levels found in ${}^{109}\mathrm{Tc}$ may indicate a change toward an oblate shape in this nucleus.

The $B(E2;I_i\to I_f)$ values for transitions in ${}_{31}^{71}{\mathrm{Ga}}_{40}$ and ${}_{31}^{73}{\mathrm{Ga}}_{42}$ were deduced from a Coulomb excitation experiment at the safe energy of $2.95$ MeV/nucleon using post-accelerated beams of ${}^{71,73}\mathrm{Ga}$ at the REX-ISOLDE on-line isotope mass separator facility. The emitted $\gamma$ rays were detected by the MINIBALL $\gamma$-detector array, and $B(E2;I_i\to I_f)$ values were obtained from the yields normalized to the known strength of the $2^{+}\to 0^{+}$ transition in the ${}^{120}\mathrm{Sn}$ target. The comparison of these new results with the data of less neutron-rich gallium isotopes shows a shift of the $E$$2$ collectivity toward lower excitation energy when adding neutrons beyond $N=40$. This supports conclusions from previous studies of the gallium isotopes, which indicated a structural change in this isotopic chain between $N=40$ and $42$. Combined with recent measurements from collinear laser spectroscopy showing a $1/2^{-}$ spin and parity for the ground state, the extracted results revealed evidence for a $1/2^{-},3/2^{-}$ doublet near the ground state in ${}_{31}^{73}{\mathrm{Ga}}_{42}$ differing by at most $0.8$ keV in energy.

The paper proposes a hybrid method for calculating scattering processes. It combines the $J$-matrix method with exterior complex scaling and an absorbing boundary condition. The wave function is represented as a finite sum of oscillator eigenstates in the inner region, and it is discretized on a grid in the outer region. The method is validated for a one- and a two-dimensional model with partial wave equations and a calculation of $p$-shell nuclear scattering with semirealistic interactions.

We develop a systematic framework for the study of the initial collision geometry fluctuations in relativistic heavy-ion collisions and investigate how they evolve through different stages of the fireball history and translate into final-particle momentum anisotropies. We find in our event-by-event analysis that only the few lowest momentum anisotropy parameters survive after the hydrodynamical evolution of the system. The geometry of the produced medium is found to be affected by the pre-equilibrium evolution of the medium and the thermal smearing of the discretized event-by-event initial conditions, both of which tend to smear out the spatial anisotropies. We find such effects to be more prominent for higher moments than for lower moments. The correlations between odd and even spatial anisotropy parameters during the pre-equilibrium expansion are quantitatively studied and found to be small. Our study provides a theoretical foundation for the understanding of initial-state fluctuations and the collective expansion dynamics in relativistic heavy-ion collisions.

We discus the proof of the equivalence of relativistic quantum mechanical models based on the generalized Bakamjian-Thomas construction in all of Dirac’s forms of dynamics. Explicit representations of the equivalent mass operators are given in all three of Dirac’s forms of dynamics.

We predict values of the magnetic moments of $T=3/2$ proton-rich $\mathit{fp}$-shell nuclei in the mass range $A=43$–$53$, by using known values for their neutron-rich mirrors together with shell-model estimates for small quantities. We extend the analysis to those $T=3/2$ $\mathit{sd}$-shell mirror pairs for which both the $T_z=-3/2$ and $T_z=+3/2$ magnetic moments have been measured. We find that these obey the same linear relation as previously deduced for $T=1/2$ mirror pairs.

The equation of state of a system of fermions in a uniform magnetic field is obtained in terms of the thermodynamic quantities of the theory by using functional methods. It is shown that the breaking of the O($3$) rotational symmetry by the magnetic field results in a pressure anisotropy, which leads to the distinction between longitudinal- and transverse-to-the-field pressures. A criterion to find the threshold field at which the asymmetric regime becomes significant is discussed. This threshold magnetic field is shown to be the same as the one required for the pure field contribution to the energy and pressures to be of the same order as the matter contribution. A graphical representation of the field-dependent anisotropic equation of state of the fermion system is given. Estimates of the upper limit for the inner magnetic field in self-bound stars, as well as in gravitationally bound stars with inhomogeneous distributions of mass and magnetic fields, are also found.

We measured the half-life of ${}^{66}\mathrm{Ga}$ by observing positrons from the ${\beta }^{+}$ branch to the ground state of ${}^{66}\mathrm{Zn}$ with a superconducting Wu-type beta spectrometer. Our result is $t_{1/2}=9.304(8)\mathrm{hours}$, which is the highest-precision measurement to date and disagrees with the Nuclear Data Sheets (NDS) value by over $6\sigma$.

The isotopic evolution of the ground-state nuclear shapes and the systematics of one-quasiproton configurations are studied in odd-$A$ Rubidium isotopes. We use a self-consistent Hartree-Fock-Bogoliubov formalism based on the Gogny energy density functional with two parametrizations, D1S and D1M, and implemented with the equal-filling approximation. We find clear signatures of a sharp shape transition at $N=60$ in both the charge radii and spin parity of the ground states, which are robust, consistent with each other, and in agreement with experiment. We point out that the combined analysis of these two observables could be used to predict unambiguously new regions where shape transitions might develop.

The lightest xenon isotopes are studied in the shell model framework, within a valence space that comprises all the orbits lying between the magic closures $N=Z=50$ and $N=Z=82$. The calculations produce collective deformed structures of triaxial nature that encompass nicely the known experimental data. Predictions are made for the (still unknown) $N=Z$ nucleus ${}^{108}\mathrm{Xe}$. The results are interpreted in terms of the competition between the quadrupole correlations enhanced by the pseudo-SU(3) structure of the positive parity orbits and the pairing correlations brought in by the $0h_{11/2}$ orbit. We also have studied the effect of the excitations from the ${}^{100}\mathrm{Sn}$ core on our predictions. We show that the backbending in this region is due to the alignment of two particles in the $0h_{11/2}$ orbit. In the $N=Z$ case, one neutron and one proton align to $J=11$ and $T=0$. In ${}^{110,112}\mathrm{Xe}$ the alignment begins in the $J=10$, $T=1$ channel and it is dominantly of neutron-neutron type. Approaching the band termination the alignment of a neutron-proton pair to $J=11$ and $T=0$ takes over. In a more academic mood, we have studied the role of the isovector and isoscalar pairing correlations on the structure on the yrast bands of ${}^{108,110}\mathrm{Xe}$ and examined the possible existence of isovector and isoscalar pairing condensates in these $N~Z$ nuclei.

In the framework of relativistic mean field (RMF) theory, we have calculated the density distribution of protons and neutrons for ${}^{40,42,44,48}\mathrm{Ca}$ with NL3 and G2 parameter sets. The microscopic proton-nucleus optical potentials for $p+{}^{40,42,44,48}\mathrm{Ca}$ systems are evaluated from the Dirac nucleon-nucleon scattering amplitude and the density of the target nucleus using relativistic-Love-Franey and McNeil-Ray-Wallace parametrizations. We have estimated the scattering observables, such as the elastic differential scattering cross section, analyzing power and the spin observables with the relativistic impulse approximation (RIA). The results have been compared with the experimental data for a few selective cases and we find that the use of density as well as the scattering matrix parametrizations are crucial for the theoretical prediction.

We consider finite-size effects on the radiative energy loss of a fast parton moving in a finite-temperature, strongly interacting medium, using the light-cone path integral formalism put forward by B. G. Zakharov [JETP Lett. 63, 952 (1996); 65, 615 (1997)]. We present a convenient reformulation of the problem that makes possible its exact numerical analysis. This is done by introducing the concept of a radiation rate in the presence of finite-size effects. This effectively extends the finite-temperature approach of Arnold, Moore, and Yaffe [J. High Energy Phys. 11 (2001) 057; 12 (2001) 009; 06 (2001) 030] (AMY) to include interference between vacuum and medium radiation. We compare results with those obtained in the regime considered by AMY, with those obtained at leading order in an opacity expansion, and with those obtained deep in the Landau-Pomeranchuk-Migdal regime.

We show that in fully self-consistent treatments of the pion, namely, its static properties and elastic and transition form factors, the asymptotic limit of the product $Q^2{G}_{{\gamma }^{*}\gamma {\pi }^0}(Q^2)$, determined a priori by the interaction employed, is not exceeded at any finite value of spacelike momentum transfer. Furthermore, in such a treatment of a vector-vector contact-interaction one obtains a ${\gamma }^{*}\gamma \to {\pi }^0$ transition form factor that disagrees markedly with all available data. We explain that the contact interaction produces a pion distribution amplitude that is flat and nonvanishing at the endpoints. This amplitude characterizes a pointlike pion bound state. Such a state has the hardest possible form factors (i.e., form factors that become constant at large momentum transfers and hence are in striking disagreement with completed experiments). However, interactions with QCD-like behavior produce soft pions, a valence-quark distribution amplitude that vanishes as $~(1-x){}^2$ for $x~1$, and results that agree with the bulk of existing data. Our analysis supports a view that the large-$Q^2$ data obtained by the BaBar Collaboration is not an accurate measure of the ${\gamma }^{*}\gamma \to {\pi }^0$ form factor.