Significant discrepancies have been observed between proton form factors as measured by Rosenbluth separation and polarization transfer techniques. There are indications that this difference may be caused by corrections to the one-photon exchange approximation that are not taken into account in standard radiative correction procedures. In this paper, we constrain the two-photon amplitudes by combining data from Rosenbluth, polarization transfer, and positron-proton scattering measurements. This allows a rough extraction of these two-photon effects in elastic electron-proton scattering and provides an improved extraction of the proton electromagnetic form factors.

Lifetimes of excited states have been measured for the positive-parity rotational bands in neutron-rich ${}^{142,144}\mathrm{Ba}$ as well as the $7^{-}$ and $9^{-}$ states of the negative-parity band in ${}^{144}\mathrm{Ba}$ using the differential Doppler shift method. The deduced quadrupole moment, $Q_t$, of the positive-parity band decreases with angular momentum and overall shows good agreement with earlier measurements. The measured lifetimes of $7^{-}$ and $9^{-}$ states are used to determine the electric dipole moment, $D_0=0.17(3)$ and 0.09(1) e fm, respectively, in the negative-parity octupole band of ${}^{144}\mathrm{Ba}$.

Using two approaches—dispersion relations and the isobar model—we have analyzed recent high precision CLAS data on cross sections of ${\pi }^0$, ${\pi }^{+}$, and $\eta$ electroproduction on protons, and the longitudinally polarized electron beam asymmetry for $p(\overrightarrow{e},e^{\text{'}}p){\pi }^0$ and $p(\overrightarrow{e},e^{\text{'}}n){\pi }^{+}$. The contributions of the resonances $P_{33}(1232)$, $P_{11}(1440)$, $D_{13}(1520)$, and $S_{11}(1535)$ to $\pi$ electroproduction and of $S_{11}(1535)$ to $\eta$ electroproduction are found. The results obtained using the two approaches are in good agreement. There is also good agreement between amplitudes of the ${\gamma }^{*}N\to S_{11}(1535)$ transition found in $\pi$ and $\eta$ electroproduction. For the first time accurate results are obtained for the longitudinal amplitudes of the $P_{11}(1440)$, $D_{13}(1520)$, and $S_{11}(1535)$ electroexcitations on protons. A strong longitudinal response is found for the Roper resonance, which rules out presentation of this resonance as a hybrid state.

We discuss the uncertainties and misinterpretations that may arise from the simultaneous plots of fusion and reaction excitation functions of different systems when weakly bound nuclei are involved, particularly halo nuclei.

The screening potential of a parton moving through a quark-gluon plasma is calculated using semiclassical transport theory. An anisotropic potential showing a minimum in the direction of the parton velocity is found. As consequences possible new bound states in the quark-gluon plasma and $J/\psi$ dissociation are discussed.

The dynamical cluster-decay model (DCM) is developed further for the decay of hot and rotating compound nuclei (CN) formed in light heavy-ion reactions. The model is worked out in terms of only one parameter, namely the neck-length parameter, which is related to the total kinetic energy TKE($T$) or effective $Q$ value ${\mathit{Q}}_{\mathrm{eff}}(T)$ at temperature $T$ of the hot CN and is defined in terms of the CN binding energy and ground-state binding energies of the emitted fragments. The emission of both the light particles (LP), with $A\le 4,Z\le 2$, as well as the complex intermediate mass fragments (IMF), with $4<A<20,Z>2$, is considered as the dynamical collective mass motion of preformed clusters through the barrier. Within the same dynamical model treatment, the LPs are shown to have different characteristics compared to those of the IMFs. The systematic variations of the LP emission cross section ${\sigma }_{\mathrm{LP}}$ and IMF emission cross section ${\sigma }_{\text{IMF}}$ calculated from the present DCM match exactly the statistical fission model predictions. A nonstatistical dynamical description is developed for the first time for emission of light particles from hot and rotating CN. The model is applied to the decay of ${{}^{56}\mathrm{Ni}}^{\ast }$ formed in the ${}^{32}\mathrm{S}+{}^{24}\mathrm{Mg}$ reaction at two incident energies $E_{\mathrm{c}\mathrm{.}\mathrm{m}\mathrm{.}}=51.6$ and 60.5 MeV. Both the IMFs and average $\stackrel{̲}{\mathit{TKE}}$ spectra are found to compare resonably well with the experimental data, favoring asymmetric mass distributions. The LPs' emission cross section is shown to depend strongly on the type of emitted particles and their multiplicities.

High-spin states in ${}^{183}\mathrm{Au}$ have been studied experimentally using the ${}^{159}\mathrm{Tb}({}^{29}\mathrm{Si},5n){}^{183}\mathrm{Au}$ reaction at a beam energy of $140\text{MeV}$. Three- or higherfold $\gamma$-ray coincidences have been measured using the detector array of GASP. The level scheme of ${}^{183}\mathrm{Au}$ was revised and extended. A rotational band proposed as the unfavored signature branch of the $\pi i_{13/2}$ band has been observed for ${}^{183}\mathrm{Au}$. Interaction properties between the two negative-signature bands of the $\pi h_{9/2}-\pi f_{7/2}$ system have been discussed for the light odd-$A$ Au nuclei.

The transverse-momentum ($Q_T$) distribution of low-mass Drell-Yan pairs is calculated in QCD perturbation theory with all-order resummation of ${\alpha }_s({\alpha }_s\ln (Q_T^2/Q^2)){}^n$ type terms. We demonstrate that the rapidity distribution of low-mass Drell-Yan pairs at large-enough transverse momentum is an advantageous source of constraints on the gluon distribution and its nuclear dependence. We argue that low-mass Drell-Yan pairs in the forward region provide a good and clean probe of small-$x$ gluons at collider energies.

Comprehensive investigations of the observed cluster radioactivity are carried out. First, the relativistic mean field (RMF) theory is employed for the calculations of the ground-state properties of relevant nuclei. The calculations reproduce the experiment well. The calculated RMF point densities are folded with the density-dependent M3Y nucleon-nucleon interaction to obtain the cluster-daughter interaction potential. This, along with the calculated and experimental $Q$ values, is used in the WKB approximation for estimating the half-lives of the parent nuclei against cluster decay. The calculations qualitatively agree with the experiment. Sensitive dependence of the half-lives on $Q$ values is explicitly demonstrated.

The isospin $I=0$ and $I=1$ kaon-nucleon $S$, $P$, $D$, $F$ wave phase shifts are studied in the chiral $\mathrm{SU}\left(3\right)$ quark model by solving the resonating group method (RGM) equation. The calculated phase shifts for different partial waves are in agreement with the experimental data. Furthermore, the structures of the $\Delta K$ states with $L=0$, $I=1$, and $L=0$, $I=2$ are investigated. We find that the interaction between $\Delta$ and $K$ in the case of $L=0$, $I=1$ is attractive, which is not like the situation of the $NK$ system, where the $S$-wave interactions between $N$ and $K$ for both $I=0$ and $I=1$ are repulsive. Our numerical results also show that when the model parameters are taken to be the same as in our previous $NN$ and $YN$ scattering calculations, the $\Delta K$ state with $L=0$ and $I=1$ is a weakly bound state with about $2\mathrm{MeV}$ binding energy, while the one with $I=2$ is unbound in the present one-channel calculation.

The collectivity of the odd-mass nucleus ${}^{55}\mathrm{Ni}$ was explored via intermediate-energy Coulomb excitation using a powerful combination of particle and $\gamma$-ray spectroscopy. A $\gamma$-ray at 2879(18) keV was observed and is interpreted to deexcite a member of the core-coupled quintuplet $2_1^{+}\left({}^{56}\mathrm{Ni}\right)\otimes \nu f_{7∕2}^{-1}$ at the same energy. By similarity with the mirror nucleus ${}^{55}\mathrm{Co}$, transition probabilities were calculated assuming $J^{\pi }=9∕2^{-}$ and $J^{\pi }=11∕2^{-}$ for this state. Both assumptions lead to a transition strength higher than predicted by a large-scale shell-model calculation using the GXPF1 effective interaction and exceed the value predicted within a simple weak-coupling approach.

We study the relativistic Hartree approach with an exact treatment of the vacuum polarization in the Walecka $\left(\sigma \text{−}\omega \right)$ model. The contribution from the vacuum polarization of the nucleon-antinucleon field to the source term of the meson fields is evaluated by performing the energy integrals of the Dirac Green function along the imaginary axis. With the present method of calculating the vacuum polarization in finite system, the total binding energies and charge radii of ${}^{16}\mathrm{O}$ and ${}^{40}\mathrm{Ca}$ can be reproduced. On the other hand, the level splittings in the single-particle level, in particular the spin-orbit splittings, are not described well because the inclusion of vacuum effect provides a large effective mass with small meson fields. We also show that the derivative expansion of the effective action is fairly useful for the estimation of the vacuum effect.

We calculate the nucleon parameters in isospin asymmetric nuclear matter using the QCD sum rules. The nucleon self-energies ${\Sigma }_v$ and ${\Sigma }_s^{*}$ are expressed in terms of the in-medium values of QCD condensates. Simple approximate expressions for the self-energies are obtained in terms of these condensates. The relation between successive inclusion of the condensates and meson-exchange picture of the nucleon interaction with medium is analyzed. The values of the self-energies and symmetry energy agree with those obtained by the methods of nuclear physics.

We report on measurements of the neutron spin asymmetries $A_{1,2}^n$ and polarized structure functions $g_{1,2}^n$ at three kinematics in the deep inelastic region, with $x=0.33$, 0.47, and 0.60 and $Q^2=2.7$, 3.5, and $4.8{(\mathrm{GeV}∕c)}^2$, respectively. These measurements were performed using a $5.7\mathrm{GeV}$ longitudinally polarized electron beam and a polarized ${}^3\mathrm{He}$ target. The results for $A_1^n$ and $g_1^n$ at $x=0.33$ are consistent with previous world data and, at the two higher-$x$ points, have improved the precision of the world data by about an order of magnitude. The new $A_1^n$ data show a zero crossing around $x=0.47$ and the value at $x=0.60$ is significantly positive. These results agree with a next-to-leading-order QCD analysis of previous world data. The trend of data at high $x$ agrees with constituent quark model predictions but disagrees with that from leading-order perturbative QCD (PQCD) assuming hadron helicity conservation. Results for $A_2^n$ and $g_2^n$ have a precision comparable to the best world data in this kinematic region. Combined with previous world data, the moment $d_2^n$ was evaluated and the new result has improved the precision of this quantity by about a factor of 2. When combined with the world proton data, polarized quark distribution functions were extracted from the new $g_1^n∕F_1^n$ values based on the quark-parton model. While results for $\Delta u∕u$ agree well with predictions from various models, results for $\Delta d∕d$ disagree with the leading-order PQCD prediction when hadron helicity conservation is imposed.

The energetics of states belonging to normal parity bands in even-even dysprosium isotopes, and their $B\left(E2\right)$ transition strengths, are studied using an extended pseudo-SU(3) shell model. States with pseudospin 1 are added to the standard pseudospin 0 space, allowing for a proper description of known excited normal parity bands. A realistic Hamiltonian is employed. Both the success of model and its limitations are discussed.

The pseudorapidity asymmetry and centrality dependence of charged hadron spectra in $d+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ are presented. The charged particle density at midrapidity, its pseudorapidity asymmetry, and centrality dependence are reasonably reproduced by a multiphase transport model, by HIJING, and by the latest calculations in a saturation model. Ratios of transverse momentum spectra between backward and forward pseudorapidity are above unity for $p_T$ below $5\mathrm{GeV}∕c$. The ratio of central to peripheral spectra in $d+\mathrm{Au}$ collisions shows enhancement at $2<p_T<6\mathrm{GeV}∕c$, with a larger effect at backward rapidity than forward rapidity. Our measurements are in qualitative agreement with gluon saturation and in contrast to calculations based on incoherent multiple partonic scatterings.

The equation of state (EOS) of dense matter and neutrino mean free path (NMFP) in a neutron star have been studied by using relativistic mean field models motivated by effective field theory. It is found that the models predict too large proton fractions, although one of the models (G2) predicts an acceptable EOS. This is caused by the isovector terms. Except G2, the other two models predict anomalous NMFP’s. In order to minimize the anomaly, besides an acceptable EOS, a large $M^{*}$ is favorable. A model with large $M^{*}$ retains the regularity in the NMFP even for a small neutron fraction.

The dynamics of nuclear collective motion is investigated in the case of reflection-asymmetric shapes. The model is based on a new parametrization of the octupole and quadrupole degrees of freedom, valid for nuclei close to the axial symmetry. Amplitudes of oscillation in other degrees of freedom different from the axial ones are assumed to be small, but not frozen to zero. The case of nuclei which already possess a permanent quadrupole deformation is discussed in some more detail and a simple solution is obtained at the critical point of the phase transition between harmonic octupole oscillation and a permanent asymmetric shape. The results are compared with experimental data of the thorium isotopic chain. The isotope ${}^{226}\mathrm{Th}$ is found to be close to the critical point.

We calculate the electromagnetic form factors of a bound proton. The chiral quark-soliton model provides the quark and antiquark substructure of the proton, which is embedded in nuclear matter. This procedure yields significant modifications of the form factors in the nuclear environment. The sea quarks are almost completely unaffected, and serve to mitigate the valence quark effect. In particular, the ratio of the isoscalar electric to the isovector magnetic form factor decreases by 20% at $Q^2=1\mathrm{Ge}{\mathrm{V}}^2$ at nuclear density, and we do not see a strong enhancement of the magnetic moment.

The structure of parity doublet rotational bands in odd actinides and medium mass nuclei is described in a cluster model. The model is based on the assumption that cluster-type shapes are produced by the motion of the nuclear system in the mass-asymmetry coordinate. The calculated rotational bands and the electric dipole transitions between the members of the parity doublet are in good agreement with the experimental data.