We produced the lowest $T=2$ state in ${}^{32}\mathrm{S}$ with the ${}^{31}\mathrm{P}$($p,\gamma$) reaction and measured the energies of the deexcitation γ rays, obtaining an excitation energy of $12047.96\pm 0.28$ keV that disagrees with a previous value of $12045.0\pm 0.4$ keV. Our result, together with a recent measurement of the ${}^{32}\mathrm{Ar}$ mass, makes the $\text{A}=32$ multiplet the most precisely measured $T=2$ quintet and provides easily the most stringent test of the isobaric multiplet mass equation. A significant violation of the isobaric multiplet mass equation is observed that could be explained by mixing with a nearby $T=0$ level.

A dynamical coupled-channels formalism for processes $\pi N\to \mathit{KY}$ and $\gamma N\to \mathit{KY}$ is presented that provides a comprehensive investigation of recent data on the $\gamma p\to K^{+}\Lambda$ reaction. The nonresonant interactions within the subspace $\mathit{KY}\oplus \pi N$ are derived from effective Lagrangians, using a unitary transformation method. The calculations of photoproduction amplitudes are simplified by casting the coupled-channels equations into a form such that the empirical $\gamma N\to \pi N$ amplitudes are input and only the parameters associated with the $\mathit{KY}$ channel are determined by performing ${\chi }^2$ fits to all of the available data for ${\pi }^{-}p\to K^{°}\Lambda ,K^{°}{\Sigma }^{°}$, and $\gamma p\to K^{+}\Lambda$. Good agreement between our models and those data are obtained. In the fits to $\pi N\to \mathit{KY}$ channels, most of the parameters are constrained within $\pm 20\%$ of the values given by the Particle Data Group and/or quark model predictions, whereas for $\gamma p\to K^{+}\Lambda$ parameters, ranges compatible with broken SU(6) ⊗ O(3) symmetry are imposed. The main reaction mechanisms in $K^{+}\Lambda$ photoproduction are singled out and issues related to newly suggested resonances $S_{11},P_{13}$, and $D_{13}$ are studied. Results illustrating the importance of using a coupled-channels treatment are reported. Meson cloud effects on the $\gamma N\to N^{*}$ transitions are also discussed.

Nuclear structure of the ${}^{102}\mathrm{Mo}$ nucleus has been studied using the ${}^{100}\mathrm{Mo}$($t,p$)${}^{102}\mathrm{Mo}$ reaction with the triton beam energy of 12 MeV obtained from the tandem Van de Graaff accelerator and a multichannel magnetic spectrograph. Proton spectra are obtained at 12 different angles from 5° to 87.5°, at an interval of 7.5° and are detected in nuclear emulsion plates. Thirty-five levels in the energy range from 0.000 to 3.248 MeV have been observed. The results yield a number of new levels with spin assignments. Absolute differential cross sections for the levels have been measured. The experimental angular distributions are compared with the theoretical distorted-wave Born approximation calculations to determine $L$ and $J^{\pi }$ values. The present results are compared with the previous results.

The thermal cross sections and resonance integrals have been determined for radiative neutron capture by ${}^{112,116,122,124}\mathrm{Sn}$ leading to the ground and isomeric states of ${}^{113,123,125}\mathrm{Sn}$ and the isomeric state of ${}^{117}\mathrm{Sn}$. Using natural samples of Sn metal foils and high-resolution $\gamma$-ray spectroscopy, it was possible to determine a mutually consistent set of cross sections, particularly the small thermal cross sections leading to $11/2^{-}$ states. A detailed analysis of the $\gamma$-ray emissions from irradiated Sn samples enabled us to make new and more precise determinations of the energies and intensities of $\gamma$ rays emitted in the decays of 40-min ${}^{123m}\mathrm{Sn}$ and 9.5-min ${}^{125m}\mathrm{Sn}$ and corresponding adjustments to the energy levels of ${}^{123,125}$Sb. The present results support the recently adopted revised value for the branching ratio of the 255.1-keV $\gamma$ ray in the decay of ${}^{113}\mathrm{Sn}$. The presence of a ${}^{116m}\mathrm{In}$ impurity in our samples prompted a new determination of the energies and intensities of the $\gamma$ rays emitted in its decay and of the energy levels in ${}^{116}\mathrm{Sn}$.

Tunneling of a harmonically bound two-body system through an external Gaussian barrier is studied in a schematic model that allows for a better understanding of intricate quantum phenomena. The role of finite size and internal structure is investigated in a consistent treatment. The excitation of internal degrees of freedom gives rise to a peaked structure in the penetration factor. The model results indicate that for soft systems the adiabatic limit is not necessarily reached, although often assumed in the fusion of nuclei and in electron screening effects at astrophysical energies.

We studied β-delayed singles-α spectra from ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$ decays with special emphasis on a careful calibration of the energy scale. ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$ activities were produced by ${}^7\mathrm{Li}$($d,p$) and ${}^6\mathrm{Li}$(${}^3\mathrm{He}$,$n$) reactions, respectively, and deposited in thin C foils. Delayed α's were counted in thin, cooled Si detectors with small solid angles to reduce summing with β's. The energy scale and detector response were calibrated with spectroscopic grade radioactive sources. We extracted the ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$ final-state continuum shapes from our spectra by using $R$-matrix analyses that included effects of lepton-recoil broadening and detector response. Our results are in excellent agreement with a recent measurement using ${}^8\mathrm{B}$'s implanted in a Si counter and in good agreement with our reanalysis of the older Wilkinson-Alburger ${}^8\mathrm{Li}$ and ${}^8\mathrm{B}$ data, but disagree with a recent ${}^8\mathrm{B}$ experiment using a coincidence technique.

The $g$ factors of several low-lying excited states of the neutron-rich ${}^{101}\mathrm{Zr}$ and ${}^{103,105}\mathrm{Mo}$ nuclei have been measured for the first time. The isotopes were produced by the spontaneous fission of a ${}^{252}\mathrm{Cf}$ source, which was sandwiched between two magnetized iron foils and placed at the center of the Gammasphere spectrometer. The $g$ factors of excited states of fission fragments were inferred from Larmor precessions deduced from the measurement of time-integrated perturbed angular correlation functions. The magnitude and sign of the quantity $(g_K-g_R)/Q_0$ were determined from the mixing ratios measured for the 3/2[411] and 5/2[532] rotational bands in ${}^{101}\mathrm{Zr}$ and ${}^{103,105}\mathrm{Mo}$. The combination of this quantity with the measured $g$ factors permitted the separation of the particle-rotor parameters $g_K$ and $g_R$ for each band. The comparison of the extracted $g_K$ factors to Nilsson model predictions confirms current band assignments, and this agreement is consistent with an axially symmetric picture of these nuclei at low spins. The possible effect of triaxial deformation on the measured magnetic moments was investigated in the rigid triaxial rotor-plus-particle framework. The calculations suggest that triaxial deformation plays a stronger role in the Mo than in the Zr isotopes, but that triaxiality is likely to be dynamic. The extracted $g_R$ factors are consistently smaller than the $Z/A$ limit, in agreement with observations in neighboring even-even nuclei.

Based on fragmentation theory extended to include the orientation degrees of freedom and higher multipole deformations up to hexadecapole deformations, the compactness of ${}^{48}\mathrm{Ca}$ induced reactions on various actinides is studied for Ds ($Z=110$) to 118 nuclei. It is shown that the reactions leading to $Z\ge 114$ nuclei are “compact” hot fusion reactions at $\theta ={90}^{°}$ orientation angles (equatorial compact or ec; collisions that are in the direction of the minor axis of the deformed reaction partner), but the ones for $Z<114$ nuclei are compact at $\theta <{90}^{°}$ (not-equatorial compact or nec). The phenomenon of “barrier distribution in orientation degrees of freedom” is observed for the first time to be related to the magnitudes of both the quadrupole and hexadecapole deformations of the deformed reaction partner. The ec configurations are obtained for the cases of quadrupole deformation alone and with small (including negative values) hexadecapole deformations. The presence of large (positive) hexadecapole deformations result in the nec configurations. These results are found to be quite general, applicable also to other lighter targets such as W and Ra with the ${}^{48}\mathrm{Ca}$ beam and to Pb based reactions. Furthermore, for compact hot fusion reactions, in addition to the ${}^{48}\mathrm{Ca}$ reaction valley, a number of other new reaction valleys (target-projectile combinations) are obtained, the most important one (next to ${}^{48}\mathrm{Ca}$) being the ${}^{54}\mathrm{Ti}$ nucleus used previously in Pb based cold fusion reaction studies but now proposed with deformed actinide nuclei such as ${}^{226}\mathrm{Ra}$, ${}^{232}\mathrm{Th}$, ${}^{238}\mathrm{U}$, and ${}^{242}\mathrm{Pu}$.

A search for self-consistent solutions for the chiral rotational bands in the $N=75$ isotones ${}^{130}\mathrm{Cs}$, ${}^{132}\mathrm{La}$, ${}^{134}\mathrm{Pr}$, and ${}^{136}\mathrm{Pm}$ is performed within the Skyrme-Hartree-Fock cranking approach using ${\mathrm{SKM}}^{*}$ and SLy4 parametrizations. The dependence of the solutions on the time-odd contributions in the energy functional is studied. From among the four isotones considered, self-consistent chiral solutions are obtained only in ${}^{132}\mathrm{La}$. The microscopic calculations are compared with the ${}^{132}\mathrm{La}$ experimental data and with results of a classical model that contains all the mechanisms underlying the chirality of the collective rotational motion. Strong similarities between the Hartree-Fock and classical model results are found. The suggestion formulated earlier by the authors that the chiral rotation cannot exist below a certain critical frequency is further illustrated and discussed, together with the microscopic origin of a transition from planar to chiral rotation in nuclei. We also formulate the separability rule by which the tilted-axis-cranking solutions can be inferred from three independent principal-axis-cranking solutions corresponding to three different axes of rotation.

We solve the generalized relativistic harmonic oscillator in $1+1$ dimensions, i.e., including a linear pseudoscalar potential and quadratic scalar and vector potentials which have equal or opposite signs. We consider positive and negative quadratic potentials and discuss in detail their bound-state solutions for fermions and antifermions. The main features of these bound states are the same as the ones of the generalized three-dimensional relativistic harmonic oscillator bound states. The solutions found for zero pseudoscalar potential are related to the spin and pseudospin symmetry of the Dirac equation in $3+1$ dimensions. We show how the charge conjugation and ${\gamma }^5$ chiral transformations relate the several spectra obtained and find that for massless particles the spin and pseudospin symmetry-related problems have the same spectrum but different spinor solutions. Finally, we establish a relation of the solutions found with single-particle states of nuclei described by relativistic mean-field theories with scalar, vector, and isoscalar tensor interactions and discuss the conditions in which one may have both nucleon and antinucleon bound states.

We study the $\pi N\to \pi \pi N$ reaction around the $N^{*}(1440)$ mass-shell energy. Considering the total cross sections and invariant mass distributions, we discuss the role of $N^{*}(1440)$ and its decay processes on this reaction. The calculation is performed by extending our previous approach [Phys. Rev. C 69, 025206 (2004)], in which only the nucleon and $\Delta (1232)$ were considered as intermediate baryon states. The characteristics in the recent data of the ${\pi }^{-}p\to {\pi }^0{\pi }^{0}n$ reaction measured by Crystal Ball Collaboration can be understood as a strong interference between the two decay processes: $N^{*}(1440)\to \pi \Delta$ and $N^{*}(1440)\to N(\pi \pi ){}_{S\text{wave}}^{I=0}$. It is also found that the scalar-isoscalar $\pi \pi$ rescattering effect in the ${\mathit{NN}}^{*}(\pi \pi ){}_{S\text{wave}}^{I=0}$ vertex, which corresponds to the propagation of σ meson, seems to be necessary for explaining the several observables of the $\pi N\to \pi \pi N$ reaction: the large asymmetric shape in the ${\pi }^0{\pi }^0$ invariant mass distributions of the ${\pi }^{-}p\to {\pi }^0{\pi }^{0}n$ reaction and the ${\pi }^{+}p\to {\pi }^{+}{\pi }^{+}n$ total cross section.

A new experiment to determine the thermonuclear cross section of the ${}^{12}\mathrm{C}$($\alpha ,\gamma$)${}^{16}\mathrm{O}$ reaction has been performed in regular kinematics using an intense α-particle beam of up to 340 μA from the Stuttgart DYNAMITRON. For the first time, a 4π-germanium-detector setup has been used to measure the angular distribution of the γ rays at all angles simultaneously. It consisted of an array of nine EUROGAM high-purity Ge detectors in close geometry, actively shielded individually with bismuth germanate crystals. The ${}^{12}\mathrm{C}$ targets were isotopically enriched by magnetic separation during implantation. The depth profiles of the implanted carbon in the ${}^{12}\mathrm{C}$ targets were determined by Rutherford backscattering for purposes of cross-section normalization and absolute determination of the $E1$ and $E2S$ factors. Angular distributions of the γ decay to the ${}^{16}\mathrm{O}$ ground state were measured in the energy range $E_{c.m.}=1.30–2.78$ MeV and in the angular range (lab.) 30°–130°. From these distributions, astrophysical $E1$ and $E2S$-factor functions vs energy were calculated, both of which are indispensable to the modeling of this reaction and the extrapolation toward lower energies. The separation of the $E1$ and $E2$ capture channels was done both by taking the phase value ${\varphi }_{12}$ as a free parameter and by fixing it using the results of elastic α-particle scattering on ${}^{12}\mathrm{C}$ in the same energy range.

The first case of a Bose-Fermi critical point symmetry, E(5/4), representing the coupling of a $j=3/2$ fermion to an E(5) core, was recently proposed. Since ${}^{134}\mathrm{Ba}$ has been found to be an empirical manifestation of E(5), we carried out a β-decay experiment to study levels in ${}^{135}\mathrm{Ba}$, where the last neutron can occupy the $2d_{3/2}$ orbit, as the first test of E(5/4). The comparison shows significant areas of agreement as well as significant discrepancies. Comparison of interacting boson-fermion approximation and shell model calculations with the data are also presented.

We present a study of fusion cross sections using a new-generation time-dependent Hartree-Fock (TDHF) code that contains no approximations regarding collision geometry and uses the full Skyrme interaction, including all of the time-odd terms. In addition, the code uses the basis-spline collocation method for improved numerical accuracy. A comparative study of fusion cross sections for ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ is made with the older TDHF results and experiments. We present results using the modern Skyrme forces and discuss the influence of the new terms present in the interaction.

Dihadron correlations at high transverse momentum $p_T$ in $d+\mathrm{Au}$ collisions at $\sqrt{s_{\mathit{NN}}}=200$ GeV at midrapidity are measured by the PHENIX experiment at the Relativistic Heavy Ion Collider. From these correlations, we extract several structural characteristics of jets: the root-mean-squared transverse momentum of fragmenting hadrons with respect to the jet $\sqrt{\langle j_T^2\rangle }$, the mean sine-squared of the azimuthal angle between the jet axes $\langle \sin {}^2{\varphi }_{\mathit{jj}}\rangle$, and the number of particles produced within the dijet that are associated with a high-$p_T$ particle ($\mathit{dN}/{\mathit{dx}}_E$ distributions). We observe that the fragmentation characteristics of jets in $d+\mathrm{Au}$ collisions are very similar to those in $p+p$ collisions and that there is little dependence on the centrality of the $d+\mathrm{Au}$ collision. This is consistent with the nuclear medium having little influence on the fragmentation process. Furthermore, there is no statistically significant increase in the value of $\langle \sin {}^2{\varphi }_{\mathit{jj}}\rangle$ from $p+p$ to $d+\mathrm{Au}$ collisions. This constrains the effect of multiple scattering that partons undergo in the cold nuclear medium before and after a hard collision.

We construct a new phenomenological nucleus-nucleus optical potential based on the interesting potential developed by Ginocchio that has the versatility to control the surface and volume regions of the potential. Using this potential with suitable energy dependence of some of the parameters, we are able to fit remarkably well experimental results of the differential scattering cross section for the ${}^{16}\mathrm{O}+{}^{28}\mathrm{Si}$ system in the center-of-mass energy $E_{c.m.}$ range from 18.67 to 90.681 MeV and the excitation function in the $E_{c.m.}$ range from 13.0 to 52.0 MeV. We also fit equally well the exhaustive experimental differential scattering data available for the ${}^{12}\mathrm{C}+{}^{24}\mathrm{Mg}$ system in the $E_{c.m.}$ range from 10.67 to 16.0 MeV. The new optical potential used has significantly fewer parameters. The results are interpreted in terms of wave mechanical aspects leading to superposition of partial waves undergoing different phase shifts generated by an optical potential characterized by volume and surface parts.

It has been shown that calculations based on our hadronic rescattering model agree reasonably well with experimental results from RHIC Au+Au collisions. Because of the large particle densities intrinsically present at the early time steps of Monte Carlo calculations attempting to model RHIC collisions undesirable artifacts resulting in non-causality may be present. The effects of such artifacts on observables calculated from the rescattering model are studied in the present work in two ways: (1) varying the time step and (2) using the subdivision method. It is shown that although non-causal artifacts are present in the rescattering model they have no appreciable effects on the calculated observables, thus strengthing the confidence in the results of this rescattering model for RHIC energies.

We determine the structure of neutron stars within a Brueckner-Hartree-Fock approach based on realistic nucleon-nucleon, nucleon-hyperon, and hyperon-hyperon interactions. Our results indicate rather low maximum masses below 1.4 solar masses. This feature is insensitive to the nucleonic part of the EOS due to a strong compensation mechanism caused by the appearance of hyperons and represents thus strong evidence for the presence of nonbaryonic “quark” matter in the interior of heavy stars.

Based on the existing experimental data of elastic scattering angular distributions and nonelastic cross sections (i.e., total reaction cross sections) for incident deuteron, by using the modified code APMN, we obtain a new optimal set of global deuteron optical potential parameters, which can fit (or reproduce) the experimental data very well for almost all target nuclei ranging from ${}^{12}\mathrm{C}$ to ${}^{238}\mathrm{U}$ in the energy region below 183 MeV.