We introduce a shell-model theory that combines traditional spherical states, which yield a diagonal representation of the usual single-particle interaction, with collective configurations that track deformations, and test the validity of this mixed-mode, oblique-basis shell-model scheme on ${}^{24}\mathrm{Mg}.$ The correct binding energy (within 2% of the full-space result) as well as low-energy configurations that have greater than 90% overlap with full-space results are obtained in a space that spans less than 10% of the full space. The results suggest that a mixed-mode shell-model theory may be useful in situations where competing degrees of freedom dominate the dynamics and full-space calculations are not feasible.

A new approach has been used to explain the experimental data for the ${}^{16}\mathrm{O}{+}^{28}\mathrm{Si}$ system over a wide energy range in the laboratory system from 29.0 to 142.5 MeV. A number of serious problems has continued to plague the study of this system for a couple of decades. The explanation of anomalous large angle scattering data; the reproduction of the oscillatory structure near the Coulomb barrier; the out-of-phase problem between theoretical predictions and experimental data; the consistent description of angular distributions together with excitation functions data are just some of these problems. These are long standing problems that have persisted over the years and do represent a challenge calling for a consistent framework to resolve these difficulties within a unified approach. Traditional frameworks have failed to describe these phenomena within a single model and have so far only offered different approaches, where these difficulties are investigated separately from one another. The present work offers a plausible framework where all these difficulties are investigated and answered. Not only does it improve the simultaneous fits to the data of these diverse observables, achieving this within a unified approach over a wide energy range, but it departs for its coupling potential from the standard formulation. This new feature is shown to improve consistently the agreement with the experimental data and has made major improvements on all the previous coupled-channels calculations for this system.

Angular correlations have been measured for the ${}^{16}\mathrm{O}{(e,e}^{\prime }{n}_0)$ and ${}^{16}\mathrm{O}{(e,e}^{\prime }{n}_3)$ reactions in the energy region $\omega =20\mathrm{}–31\hspace{0.5em}\mathrm{MeV}$ at a momentum transfer of 0.33 ${\mathrm{fm}}^{-1}.$ They indicate dominance of the giant dipole resonance. The data are compared with a random-phase approximation calculation. A predicted backward-peaked angular correlation in the neutron decay, due to interference between the $T=0\mathrm{}$ and $T=1\mathrm{}$ resonances, was not observed. Legendre coefficients extracted from the angular correlation data suggest the existence of a broad $E2\mathrm{}$ resonance over the giant dipole resonance region. The opposite signs of the correlation parameters $b_1$ and $b_3$ for the ${}^{16}\mathrm{O}{(e,e}^{\prime }{n}_0)$ and ${}^{16}\mathrm{O}{(e,e}^{\prime }{p}_0)$ reactions suggest that the $E2\mathrm{}$ resonance below about 22 MeV is isoscalar. Above about 22 MeV, large positive values for $b_1$ and $b_2$ in ${}^{16}\mathrm{O}{(e,e}^{\prime }{p}_0)$ compared to small ones in ${(e,e}^{\prime }{n}_0)$ reflect the contribution resulting from the direct-knockout process in ${(e,e}^{\prime }{p}_0).\mathrm{}$ The angular correlations for ${}^{16}\mathrm{O}{(e,e}^{\prime }{n}_3)$ and ${}^{12}\mathrm{C}{(e,e}^{\prime }{n}_0)$ were confirmed to be similar as expected from the similarity of their particle-hole configurations. The good agreement including the fine structure between the form factors for ${}^{16}\mathrm{O}{(e,e}^{\prime }{n}_0)$ and ${}^{16}\mathrm{O}\left(\gamma {,n}_0\right)$ confirmed the dominance of the giant dipole resonance in this energy region.

We derive a general expression for the multipole expansion of the electromagnetic interaction in relativistic heavy-ion collisions, which can be employed in higher-order dynamical calculations of Coulomb excitation. The interaction has diagonal as well as off-diagonal multipole components, associated with the intrinsic and relative coordinates of projectile and target. A simple truncation in the off-diagonal components gives excellent results in first-order perturbation theory for distant collisions and for beam energies up to 200 MeV/nucleon.

The effect of continuum couplings in the fusion of the halo nucleus ${}^{11}\mathrm{Be}$ on ${}^{208}\mathrm{Pb}$ around the Coulomb barrier is studied using a three-body model within a coupled discretized continuum channels formalism. We investigate in particular the role of continuum-continuum couplings. These are found to hinder total, complete, and incomplete fusion processes. Couplings to the projectile ${1p}_{1/2}$ bound excited state redistribute the complete and incomplete fusion cross sections, but the total fusion cross section remains nearly constant. Results show that continuum-continuum couplings enhance the irreversibility of breakup and reduce the flux that penetrates the Coulomb barrier. Converged total fusion cross sections agree with the experimental ones for energies around the Coulomb barrier, but underestimate those for energies well above the Coulomb barrier.

We investigate the structure of the SU(3) s-wave octet and decuplet baryons employing a constituent chiral quark model. We solve a three quark system with the many range Gaussian bases, which allow the baryon to have a [21] flavor-spin symmetry as well as the usual [3] symmetry. The method which we employ here has been shown to work quite nicely to describe the nucleon and $\Delta$ structure. We extend this method in order to take into account a mass difference between ud and strange quarks for both kinetic energy and potential terms. Furthermore we improve the method in order to take care of the strong short range attraction due to the pseudoscalar meson exchange potential. It is found that all octet baryons gain a very strong attraction in the chiral quark model when the semirelativistic approach, namely, the relativistic expression only for the kinetic energy term is employed. It is also found that an inclusion of the additional attraction due to the sigma meson exchange and one gluon exchange potential makes the system unstable in the semirelativistic approach.

We apply the perturbative chiral quark model to the study of the low-energy $\pi N$ interaction. Using an effective chiral Lagrangian we reproduce the Weinberg-Tomozawa result for the S-wave $\pi N$ scattering lengths. After inclusion of the photon field we give predictions for the electromagnetic ${O(p}^2)$ low-energy couplings of the chiral perturbation theory effective Lagrangian that define the electromagnetic mass shifts of nucleons and first-order ${(e}^2)$ radiative corrections to the $\pi N$ scattering amplitude. Finally, we estimate the leading isospin-breaking correction to the strong energy shift of the ${\pi }^{-}p$ atom in the $1s$ state, which is relevant for the experiment “pionic hydrogen” at PSI.

It was suggested earlier that, due to the statistical properties of complicated many-body dynamics, the energies of low-lying nuclear states in large shell model spaces converge to their exact values exponentially as a function of the dimension in progressive truncation. Applying the exponential convergence algorithm as a practical method of extrapolation we calculated ground-state energies, spins, and isospins of the lowest $|\Delta \left(N-Z\right)|$ nuclides from ${}^{42}\mathrm{Ca}$ to ${}^{56}\mathrm{Ni}$ using the $\mathrm{fp}$-shell model and the FPD6 interaction. The binding energies relative to ${}^{40}\mathrm{Ca}$ are compared with the experimental values. The deviation can be accounted by adding monopole terms to the single-particle energies and two-body matrix elements.

We employ a propagator technique to derive a new relativistic $1/|\mathit{q}|$ expansion of the structure function of a nucleus, composed of point nucleons. We exploit nonrelativistic features of low-momentum nucleons in the target and only treat relativistically the nucleon after absorption of a high-momentum virtual photon. The new series permits a three-dimensional reduction of each term and a formal summation of all final state interaction terms. We then show that a relativistic structure function can be obtained from its nonrelativistic analog by a mere change of a scaling variable and the addition of an energy shift. We compare the obtained result with an ad hoc generalized Gersch-Rodriguez-Smith theory, previously used in computations of nuclear structure functions.

Differential cross sections are presented for the inclusive production of charged pions in the momentum range $0.1–1.2\hspace{0.5em}\mathrm{GeV}/c$ in interactions of 12.3 and $17.5\hspace{0.5em}\mathrm{GeV}/c$ protons with Be, Cu, and Au targets. The measurements were made by Experiment 910 at the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory. The cross sections are presented as a function of pion total momentum and production polar angle $\theta$ with respect to the beam.

Using the quantum molecular dynamics model coupled with the minimum spanning tree clusterization algorithm, we investigate the system-size effects in the production of light mass fragments (with mass $<~10).$ This was achieved by simulating the collision of symmetric nuclei like $\mathrm{Ca}+\mathrm{Ca},$ $\mathrm{Ni}+\mathrm{Ni},$ $\mathrm{Nb}+\mathrm{Nb},$ $\mathrm{Xe}+\mathrm{Xe},$ $\mathrm{Er}+\mathrm{Er},$ $\mathrm{Au}+\mathrm{Au},$ and $\mathrm{U}+\mathrm{U}$ at incident energies between 50 MeV/nucleon and 1 GeV/nucleon and over full range of impact parameter. Our detailed analysis shows that the triggering of the multifragmentation and its saturation is delayed in heavier systems. The striking result, which is independent of the incident energy as well as of the impact parameter, is that the mass dependence of the multiplicity of any kind of fragment exhibits a power law behavior $\propto A_{\mathrm{tot}}^{\tau },$ where $“A_{\mathrm{tot}}”$ is the mass of the composite system. Similar mass dependencies have already been reported in the literature for the fusion process at low incident energy as well as for the production of kaon and collective flow (and its disappearance) at intermediate energies. As reported for the production of kaons, the parameter $\tau$ depends on the colliding geometry as well as on the incident energy. No unique dependence of $\tau$ (such as, in the case of disappearance of flow) exists. The value of the parameter $\tau$ in central low energy collisions is close to 2/3, which suggests the dominance of the mean field. On the other hand, a linear dependence occurs at higher incident energies. Similar trends can also be seen in the preliminary reports of the FOPI experiments.

We study the production of ${\eta }^{\prime }$ from hadronizing thermal gluons using recently proposed ${\eta }^{\prime }-g-g$ effective vertex. The ${\eta }^{\prime }$ yield is found to be sensitive to the initial condition. At RHIC and LHC, the enhancement is large enough to be easily detected.

The ${}^{239}\mathrm{Pu}{\mathrm{}(n,2n)\mathrm{}}^{238}\mathrm{Pu}$ cross section has been deduced using a combination of measured partial $\gamma$-ray cross sections and enhanced Hauser-Feshbach reaction modeling from threshold to $E_n<~20\hspace{0.5em}\mathrm{MeV}.$ Eight ${}^{239}\mathrm{Pu}(n,2n\gamma {)}^{238}\mathrm{Pu}$ partial $\gamma$-ray cross sections were measured using the GEANIE spectrometer, the time-of-flight technique, and energetic neutrons produced at the LANSCE/WNR facility. The $\mathrm{}(n,2n)\mathrm{}$ cross section was obtained by multiplying the sum of observed noncoincident partial $\gamma$-ray cross sections by the calculated ratio of the $\mathrm{}(n,2n)\mathrm{}$ cross section divided by the sum of the same partial $\gamma$-ray cross sections. A comparison between the data and model calculations indicates potential deficiencies in the modeling of the $\gamma$-ray cascade.

High-spin states in ${}^{129}\mathrm{Nd}$ were populated in the reaction ${}^{92}\mathrm{Mo}{(}^{40}\mathrm{Ca},2pn)$ with beam energies of 170 and 184 MeV in two separate experiments. Over 140 new transitions were placed in a level scheme that consists of four rotational structures, three of which have been observed for the first time. The bands were assigned configurations based on their $B\left(M1\mathrm{}\right)/B\left(E2\mathrm{}\right)\mathrm{}$ ratios (for the strongly coupled bands), aligned angular momentum, observed band crossings, and signature splitting. Evidence for of the observation of the deformation driving $\nu i_{13/2}\left[660\right]1/2$ orbital is presented. Signature splitting trends in the $\nu h_{11/2}$ bands of $A\sim 130$ nuclei are investigated within the framework of the cranked shell model. Comparisons are made with observations in the $\pi h_{11/2}$ bands near $A\sim 160.$

Properties of the ground and several collective excited states of selected neutron-rich $N=28\mathrm{}$ isotones and sulfur isotopes around ${}^{44}\mathrm{S}$ are described in the framework of the angular momentum projected generator coordinate method using the quadrupole moment as collective coordinate and the Gogny force, with the D1S parametrization, as the effective interaction. Fairly good agreement with available experimental data is obtained for the $2^{+}$ excitation energies and $B\left(E2\mathrm{}\right)\mathrm{}$ transition probabilities of the $N=28\mathrm{}$ isotones. For the sulfur isotopes an acceptable agreement is found and the isotopic trend is well reproduced. It is found that the $N=28\mathrm{}$ shell closure is not preserved in the prolate ${}^{40}\mathrm{Mg},$ the oblate deformed ${}^{42}\mathrm{Si},$ and the shape coexistent isotones ${}^{44}\mathrm{S}$ and ${}^{46}\mathrm{Ar},$ whereas it is preserved (on the average) in ${}^{48}\mathrm{Ca}.$ The sulfur isotopes ${}^{38-42}\mathrm{S}$ are found to be, to some extent, prolate deformed.

The level properties in the low energy region of ${}^{125,127}\mathrm{Ba}$ were studied through the decays of ${}^{125,127}\mathrm{La}$ by using the JAERI on-line mass separator (JAERI-ISOL). The half-lives of the excited states and the internal conversion coefficients were determined for the first time by the β-γ delayed coincidence technique and by conversion electron measurements, respectively. The half-life of the long-lived isomeric state of ${}^{127}\mathrm{Ba}$ (1.93 s) was determined by spectrum multiscaling measurements. Although the detailed decay schemes have been proposed, no evidence of a parity doublet has been observed. The level properties with respect to the transition probabilities are well interpreted by the Nilsson model.

The relativistic light-front dynamics (LFD) method has been shown to give a correct description of the most recent data for the deuteron monopole and quadrupole charge form factors obtained at the Jefferson Laboratory for elastic electron-deuteron scattering for six values of the squared momentum transfer between 0.66 and 1.7 $(\mathrm{GeV}{/c)}^2.$ The good agreement with the data is in contrast with the results of the existing nonrelativistic approaches. In this work we first make a complementary test of the LFD applying it to calculate another important characteristic, the nucleon momentum distribution $n\left(q\right)\mathrm{}$ of the deuteron, using six invariant functions $f_i$ $(i=1,\dots ,6)$ instead of two $(S$ and D waves) in the nonrelativistic case. The comparison with the y-scaling data shows the decisive role of the function $f_5$ which at $q>~500\mathrm{MeV}/c$ exceeds all other f functions (as well as the S and D waves) for the correct description of $n\left(q\right)\mathrm{}$ of the deuteron in the high-momentum region. Comparison with other calculations using S and D waves corresponding to various nucleon-nucleon potentials is made. Second, using clear indications that the high-momentum components of $n\left(q\right)\mathrm{}$ in heavier nuclei are related to those in the deuteron, we develop an approach within the natural orbital representation to calculate $n\left(q\right)\mathrm{}$ in $\mathrm{}(A,Z)\mathrm{}$ nuclei on the basis of the deuteron momentum distribution. As examples, $n\left(q\right)\mathrm{}$ in ${}^4\mathrm{He},$ ${}^{12}\mathrm{C},$ and ${}^{56}\mathrm{Fe}$ are calculated and good agreement with the y-scaling data is obtained.

This work reports on the first observation of excited levels in the ${}^{139}\mathrm{I}$ nucleus. Levels in ${}^{139}\mathrm{I},$ populated in spontaneous fission of ${}^{248}\mathrm{Cm},$ were studied by means of prompt $\gamma$-ray spectroscopy, using the EUROGAM2 array. The level scheme of ${}^{139}\mathrm{I}$ obtained in this work shows patterns characteristic of a spherical vibrator, which result from a weak interaction of the ${}^{138}\mathrm{Te}$ core with the odd proton. No signs of octupole correlations were observed in ${}^{139}\mathrm{I}.$ The new data allow, for the first time systematic predictions to be made of energies and spins of states in the ${}^{137}\mathrm{Sb}$ nucleus, helping the future studies of the r-process nuclei at the $Z=50\mathrm{}$ line.

Using the statistical model with collective enhancement of the level density, and the fission and neutron evaporation characteristics predicted in different theoretical models, we analyze the survival probabilities of even-even and odd superheavy nuclei. The dependence of the obtained results on the model input is discussed. The role of the collective enhancement factors in the level density is treated. For $Z>~114,$ the calculated ratios of the neutron evaporation width to the fission width and thus evaporation residue cross sections are strongly different with various models predicting nuclear properties.

Self-consistent Hartree-Fock-Bogoliubov (HFB) calculations have been performed with the Gogny force for nuclei along several constant Z and constant N chains, with the purpose of extracting the macroscopic part of the binding energy using the Strutinsky prescription. The macroscopic energy obtained in this way is compared to current liquid-drop formulas. The evolution of the single-particle levels derived from the HFB calculations along the constant Z and constant N chains and the variations of the different kinds of nuclear radii are also analyzed. Those radii are shown to follow isospin-dependent three parameter laws close to the phenomenological formulas which reproduce experimental data.