Higher-order effects in the Coulomb dissociation of halo nuclei are investigated by comparing the first-order perturbation theory to the numerical resolution of a time-dependent Schrödinger equation. The calculations are performed for the breakup on a lead target of ${}^{11}\mathrm{Be}$ and ${}^8\mathrm{B}$. The populations of the different partial waves composing the ${}^{10}\mathrm{Be}$-neutron or ${}^7\mathrm{Be}$-proton continuum reveal that couplings in the continuum remain significant even at high impact parameters and high projectile-target relative velocities. Although the total breakup cross section is fairly well described by a first-order approximation, its partial-wave components reached by the first-order transitions are significantly depleted toward other partial waves after the closest approach. The information extracted by assuming the validity of the first-order approximation is affected by an energy distortion. Another distortion is caused by the presence of a resonance as exemplified by the $5/2^{+}$ resonance of ${}^{11}\mathrm{Be}$. Such effects may partly explain discrepancies between direct and indirect measurements of the astrophysical S factor of the ${}^7\mathrm{Be}(\text{p},\gamma ){}^8\mathrm{B}$ reaction at stellar energies.

Multinucleon transfer reactions in ${}^{40}\mathrm{Ca}+{}^{208}\mathrm{Pb}$ have been studied at bombarding energies close to the Coulomb barrier. Projectilelike fragments have been identified in nuclear mass and charge with a time-of-flight spectrometer. Angular and total kinetic energy loss distributions and inclusive cross sections have been compared with those of semiclassical models. The analysis shows that a successive transfer mechanism of single nucleons does not account for the data, and a direct nucleon pair transfer has to be included in the description. Nucleon evaporation effects are taken into account.

Low-lying bound states of the neutron-rich boron isotopes, ${}^{15}\mathrm{B}$ and ${}^{17}\mathrm{B}$, have been investigated using the ${}^{15,17}\mathrm{B}+{}^{12}\mathrm{C}$ inelastic scatterings at approximately 70 MeV/nucleon. In-beam γ-ray spectroscopy was used to determine the energy levels of the excited states, and the angular distribution of the particle in the inelastic channel populating each state was measured. Two bound states were observed for ${}^{15}\mathrm{B}$, while a new bound excited state was found for ${}^{17}\mathrm{B}$ at $E_x=1.07(1)\hspace{1em}\mathrm{MeV}$ very close to the neutron emission threshold $(S_{2n}=1.39\hspace{1em}\mathrm{MeV})$. The angular distributions for the transitions to these states are well reproduced with $\Delta L^{\pi }=2^{+}$ diffraction patterns. The energy levels and $\Delta L^{\pi }=2^{+}$ are consistent with shell model predictions. The quadrupole deformation lengths for the transitions extracted from the differential cross sections are compared to the shell model, suggesting a strong quenching of the neutron effective charge both for ${}^{15}\mathrm{B}$ and ${}^{17}\mathrm{B}$.

We present a systematic analysis of two-pion interferometry in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ using the STAR detector at Relativistic Heavy Ion Collider. We extract the Hanbury-Brown and Twiss radii and study their multiplicity, transverse momentum, and azimuthal angle dependence. The Gaussianness of the correlation function is studied. Estimates of the geometrical and dynamical structure of the freeze-out source are extracted by fits with blast-wave parametrizations. The expansion of the source and its relation with the initial energy density distribution is studied.

We give a systematic analysis of α decays to low-lying $2^{+}$ states in even-even nuclei. Collective excitations are considered within the spherical quasiparticle random-phase approximation. We use realistic G-matrix elements of the Bonn interaction as a residual two-body force. The only free parameters are the ratio between the isovector and isoscalar strengths and proton-neutron asymmetry. The formalism can reproduce the main experimental trends versus the excitation energy for both the $B(E2)$ values and the α-decay hindrance factors. We reproduced most of the available data by using one common parametrization. It turns out that the fine structure of the α decay is more sensitive than electromagnetic transitions as a tool for investigating nuclear interaction. With the adopted parametrization, we predict $B(E2)$ values and α-decay hindrance factors in even-even nuclei.

The g factor of the $2_1^{+}$ state of radioactive ${}^{68}\mathrm{Ge}$ ($T_{1/2}=270$ d) has been measured for the first time. The technique used is based on α transfer from a ${}^{12}\mathrm{C}$ target to energetic ${}^{64}\mathrm{Zn}$ projectiles that incorporates the favorable conditions of inverse kinematics as in projectile Coulomb excitation. It also includes features of the transient field technique applied to nuclear spin precessions. Because the reaction cross section is large the method is a significant alternative to Coulomb excitation of low-intensity radioactive ion beams. In addition, we have remeasured the lifetimes of several excited states using the Doppler-shift-attenuation method. In these measurements, the inherent focusing nature of the reaction in the forward direction was optimally exploited for the resulting fast-moving nuclei. The g factor value obtained, $g(2_1^{+})=+0.55(14)$, is in good agreement with the collective value, $g=Z/A=0.47$, and is also consistent with the precise data of the stable even-A Ge isotopes. The newly determined lifetimes partially agree with those quoted in the literature and are of comparable accuracy. The deduced $B(E2)$ values and the new measured g factor are well reproduced by some fp shell model calculations in which excitations from the $f_{7/2}$ orbital play an important role.

Development of neutron-rich radioactive beams at the Holifield Radioactive Ion Beam Facility has stimulated experimental and theoretical activity in heavy Sn and Te isotopes. Recently, the g factor of the first $2^{+}$ state in ${}^{132}\mathrm{Te}$ has been measured. We report here new shell-model calculation of magnetic moments for selected Sn and Te isotopes. The residual interaction is based on the CD-Bonn renormalized $G$ matrix. Single-particle spin and orbital effective g factors are evaluated microscopically including core polarization and meson exchange currents effects.

We discuss a sum rule satisfied by the correlation function of two particles with small relative momenta. The sum rule, which results from the completeness condition of the quantum states of two particles, is derived and checked to see how it works in practice. The sum rule is shown to be trivially satisfied by free particle pairs. We then analyze three different systems of interacting particles: neutron and proton pairs in the s-wave approximation, the so-called hard spheres with phase shifts taken into account up to $l=4$, and finally, the Coulomb system of two charged particles.

We proceed to a critical examination of the method used in nuclear fragmentation to exhibit signals of negative heat capacity. We show that this method leads to unsatisfactory results when applied to a simple and well controlled model. These discrepancies are due to an incomplete evaluation of the internal potential energy of the fragments and to the neglect of their mutual interaction. This persists even at quite low densities.

Transverse momentum spectra of pions, protons, and antiprotons in $\mathrm{Au}+\mathrm{Au}$ collisions at intermediate RHIC energy $\sqrt{s_{\mathit{NN}}}=62\mathrm{GeV}$ are studied in a model that includes both quark coalescence from the dense partonic matter and fragmentation of the quenched perturbative minijet partons. The resulting baryon to meson ratio at intermediate transverse momenta is predicted to be larger than that seen in experiments at higher center of mass energies.

γ-ray spectroscopy of ${}^{132}\mathrm{Te}$, obtained from ${\beta }^{-}$ decay of a ${}^{132}\mathrm{Sb}$ radioactive beam at the Holifield Radioactive Ion Beam Facility, was performed using the Clarion array. A significantly revised γ-decay scheme for ${}^{132}\mathrm{Te}$ was obtained including a number of new, likely $2^{+}$, states below 2.5 MeV and the removal of a $3^{-}$ state at 2280 keV. A simple shell-model interpretation is discussed for the low-lying levels.

We present the first ab initio structure investigation of the loosely bound ${}^{11}\mathrm{Be}$ nucleus, together with a study of the lighter isotope ${}^9\mathrm{Be}$. The nuclear structure of these isotopes is particularly interesting because of the appearance of a parity-inverted ground state in ${}^{11}\mathrm{Be}$. Our study is performed in the framework of the ab initio no-core shell model. Results obtained using four different, high-precision two-nucleon interactions, in model spaces up to $9\hslash \Omega$, are shown. For both nuclei, and all potentials, we reach convergence in the level ordering of positive- and negative-parity spectra separately. Concerning their relative position, the positive-parity states are always too high in excitation energy, but a fast drop with respect to the negative-parity spectrum is observed when the model space is increased. This behavior is most dramatic for ${}^{11}\mathrm{Be}$. In the largest model space we were able to reach, the $1/2^{+}$ level has dropped down to become either the first or the second excited state, depending on which interaction we use. We also observe a contrasting behavior in the convergence patterns for different two-nucleon potentials and argue that a three-nucleon interaction is needed to explain the parity inversion. Furthermore, large-basis calculations of ${}^{13}\mathrm{C}$ and ${}^{11}\mathrm{B}$ are performed. This allows us to study the systematics of the position of the first unnatural-parity state in the $N=7$ isotone and the $A=11$ isobar. The ${}^{11}\mathrm{B}$ run in the $9\hslash \Omega$ model space involves a matrix with dimension exceeding $1.1\times {10}^9$, and is our largest calculation so far. We present results on binding energies, excitation spectra, level configurations, radii, electromagnetic observables, and ${}^{10}\mathrm{Be}+n$ overlap functions.

Recently, the restricted angular momentum variation after projection method, using the quadrupole degree of freedom as a variational coordinate in conjunction with effective interactions of the Skyrme or Gogny type, has been used very successfully to study a variety of phenomena concerning the quadrupole degree of freedom. In this paper, we study the quality of such an approach by considering additional degrees of freedom as variational coordinates: the hexadecapole moment and the fluctuations on the quadrupole moment, particle number, and angular momentum operators. The study has been performed with the Gogny interaction ($D1S$ parametrization) for the nuclei ${}^{32}\mathrm{Mg}$ and ${}^{34}\mathrm{Mg}$. The results of the angular momentum projection and the subsequent generator coordinate calculations show that the extra degrees of freedom considered are irrelevant for the description of the lowest lying states for each angular momentum.

We apply a contour deformation technique in momentum space to the newly developed Gamow shell model, using the drip-line nuclei ${}^5\mathrm{He}$, ${}^6\mathrm{He}$, and ${}^7\mathrm{He}$ as test cases. A major problem in Gamow shell-model studies of nuclear many-body systems is the increasing number of many-body configurations due to the large number of resonant and complex-continuum single-particle orbits necessary to reproduce multiparticle bound and resonant states. We address this problem using two different effective operator approaches generalized to the complex momentum plane. These are the Lee-Suzuki similarity transformation method for complex interactions and the multireference perturbation theory method. We show that a combination of these two approaches results in a drastic truncation of the number of relevant configurations compared with direct diagonalization. This offers interesting perspectives for studies of weakly bound systems.

The 1 GeV proton-induced reaction on ${}^{208}\mathrm{Pb}$ targets is analyzed by using the percolation model combined with the Atchison fission model. The fragment mass distribution and the isotopic production cross sections obtained from our model are compared with the experimental data. The trends of the fragment mass distribution for the 1 GeV proton-induced reaction can be reproduced by our calculation in some degree. The order of magnitude for the calculated isotopic production cross sections at the calculated peak positions is similar to that of the experimental peak values. The calculated peak positions of the isotopic production cross sections are shifted to the heavier region than those of the experimental data.

Approximations made in implementing the transfer-to-the-continuum model for single-nucleon knockout reactions on light target nuclei are investigated using more complete numerical calculations. The reliability of different proposed approximation schemes and their predicted cross sections are discussed. The results of the model calculations that use realistic descriptions of the distorting interactions entering the theory are also compared with available experimental data for reactions induced by ${}^{15}\mathrm{C}$ and ${}^{34}\mathrm{Si}$ secondary beams. These transitions, with different neutron orbital angular momenta, also have significantly different values of the neutron separation energy. The different approximation schemes are shown to agree most closely for the weakly bound and spatially extended, $l=0,{}^{15}\mathrm{C}$ ground state transition. For an $l=2$ transition in ${}^{34}\mathrm{Si}$, the approximation schemes are shown to be dependent on the nucleon separation energy. In all cases comparisons of even the most accurate implementation of the theory with the experimental data reveals deviations in both the magnitudes of the predicted integrated cross sections and their momentum distributions. Furthermore, the use of the different approximation schemes also produce quite significant effects on the shapes of the predicted momentum distributions and the integrated partial cross sections.

The ${}^{12}\mathrm{C}$(${}^{12}\mathrm{C}$,${}^8\mathrm{Be}+{}^{12}\mathrm{C}$($0_2^{+}$))${}^4\mathrm{He}$ reaction has been studied with beam energies of 82–120 MeV to search for excited states in ${}^{20}\mathrm{Ne}$ that decay into ${}^8\mathrm{Be}+{}^{12}\mathrm{C}$($0_2^{+}$). The detection of five of the six final-state α particles in an array of eight, sixteen-element, strip detectors permitted the full reconstruction of the reaction kinematics. Two ${}^{20}\mathrm{Ne}$ resonances at 35.2 and 36.5 MeV are observed, particularly at beam energies less than 93 MeV. An analysis of the angular correlations associated with the observed resonances indicates that an angular momentum of $10\hslash$ is important in this region, and thus it is possible that at least one of the resonances possesses $J^{\pi }={10}^{+}$.

The effect of vacuum polarization on the parity violating asymmetry in elastic electron-nucleus scattering is considered. Calculations are performed in the high-energy approximation, with an exact treatment of the electric field of the nucleus. It is shown that the radiative correction to the parity violating asymmetry is logarithmically enhanced and the value of the correction is about $-1\%$.

High-precision measurements of the half-life and β-branching ratios for the ${\beta }^{-}$ decay of ${}^{26}\mathrm{Na}$ to ${}^{26}\mathrm{Mg}$ have been measured in β-counting and γ-decay experiments, respectively. A 4π proportional counter and fast tape transport system were employed for the half-life measurement, whereas the γ rays emitted by the daughter nucleus ${}^{26}\mathrm{Mg}$ were detected with the $8\pi$ γ-ray spectrometer, both located at TRIUMF's isotope separator and accelerator radioactive beam facility. The half-life of ${}^{26}\mathrm{Na}$ was determined to be $T_{1/2}=1.07128\pm 0.00013\pm 0.00021\text{s}$, where the first error is statistical and the second systematic. The logft values derived from these experiments are compared with theoretical values from a full sd-shell model calculation.