A two-baryon coupled-channel potential is developed. It couples two-nucleon states and states in which one nucleon is turned into a $\Delta$ isobar. It is developed as extension of the purely nucleonic charge-dependent (CD) Bonn potential. It is fitted to two-nucleon scattering data up to 350 MeV nucleon lab energy. Since scattering energies just touch the pion-production threshold, the $\Delta$ isobar is considered a stable baryon. The resulting fit of the coupled-channel potential is of the same quality as that for CD Bonn. The coupled-channel potential is as realistic as CD Bonn and as any other modern two-nucleon potential. It is charge-dependent as CD Bonn. It is employed for the description of elastic and inelastic three-nucleon scattering. The $\Delta$ isobar yields an effective three-nucleon force in the three-nucleon system, besides other effects. $\Delta$-isobar effects in three-nucleon scattering are isolated and discussed.

Highly excited states of ${}^{10}\mathrm{Be}$ are formed by the bombardment of ${}^7\mathrm{Li}$ targets by ${}^7\mathrm{Li}$ beams at 34 and 50.9 MeV from the Florida State University Tandem/LINAC accelerator facility. The states are observed in three-body final state reactions by coincidence measurement of the vector momenta of two of the three particles and reconstruction of the decay energies. We observe decays involving ${}^7\mathrm{Li},$ ${}^8\mathrm{Li},$ ${}^9\mathrm{Li},$ and ${}^6\mathrm{He}$ in their ground states, first excited states, and in some cases second excited states. Fifteen of the 18 excitations observed are proposed as possible new states of ${}^{10}\mathrm{Be}.$ A few $\alpha$-particle decays of excited boron isotopes are also reported.

The excitation of the double-phonon giant dipole resonance was observed in heavy projectile nuclei impinging on targets of high nuclear charge with energies of 500–700 MeV/nucleon. New experimental data are presented for ${}^{136}\mathrm{Xe}$ and ${}^{238}\mathrm{U}$ together with further analysis of earlier data on ${}^{208}\mathrm{Pb}.$ Differential cross sections $d\sigma {/dE}^{*}$ and $d\sigma /d\theta$ for electromagnetic excitations were deduced. Depending on the isotope, cross sections appear to be enhanced in comparison to those expected from a purely harmonic nuclear dipole response. The cumulative effect of excitations of two-phonon states composed of one dipole and one quadrupole phonon, of predicted anharmonicities in the double-phonon dipole response, and of damping of the dipole resonance during the collision may account for the discrepancy. In addition, decay properties of two-phonon resonances were studied and compared to that of a statistical decay.

High-spin states in the doubly odd $N=77\mathrm{}$ nucleus ${}^{132}\mathrm{Cs}$ have been studied. The known positive-parity structures have been extended. $\gamma$-ray linear-polarization and angular-correlation measurements have been performed to establish the spin and parity assignment of these structures. A new chiral partner of the $\pi h_{11/2}\otimes \nu h_{11/2}$ band has been proposed. Three-dimensional tilted axis cranking model calculations have been performed and compared with the experimental results.

Average multiplicities and transverse momenta of hadrons are calculated using a microcanonical hadronization description for a cluster of given total energy and volume. As a function of the total energy, we determine the critical volume above which the microcanonical description coincides with the canonical one, and compare the results with those obtained using one of the standard canonical models. We show that the critical volume depends on the energy and the mass of the hadrons. For heavy particles, volumes above $50{\mathrm{fm}}^3$ are needed, even more than $100{\mathrm{fm}}^3$ if one considers transverse momenta. Thus the prediction of heavy hadron multiplicities in $pp,Kp,$ and $e^{+}{e}^{-}$ reactions requires a microcanonical approach, whereas for heavy-ion reactions a canonical calculation is valid. We conclude by showing the importance of the feeding for the observed hadron multiplicities.

We have analyzed the NA50 data on the centrality dependence of $p_T$ broadening of $J/\psi \mathrm{’}\mathrm{s}$ in $\mathrm{Pb}+\mathrm{Pb}$ collisions at the CERN-SPS. The data were analyzed in a QCD based model, where $J/\psi \mathrm{’}\mathrm{s}$ are suppressed in “nuclear” medium. Without any free parameter, the model could explain the NA50 $p_T$ broadening data. The data were also analyzed in a quark-gluon plasma (QGP) based threshold model, where $J/\psi$ suppression is 100% above a critical density. The QGP based model could not explain the NA50 $p_T$ broadening data. We have also predicted the centrality dependence of $J/\psi$ suppression and $p_T$ broadening at RHIC energy. Both models, the QGP based threshold model and the QCD based nuclear absorption model, predict $p_T$ broadening very close to each other.

The medium effect on the pion distribution at high $p_T$ in $\mathrm{AA}$ collisions is compared to that of the pion distribution at high $p_L$ in $\mathrm{pA}$ collisions. Both the suppression of the spectra and the energy losses of the measured pions are studied. Although the medium effect on $p_T$ is larger than on $p_L,$ the difference is found surprisingly to be not as big as one would naively expect.

Event-to-event fluctuation in multipion production in ${}^{32}\mathrm{S}$-AgBr interactions at $200A\mathrm{GeV}$ has been investigated in terms of the newly defined erraticity measures $\chi \mathrm{}(p,q),$ ${\chi }_q^{\prime },$ ${\omega }_q,$ ${\mu }_q^{\prime },$ and $r_q$ proposed by Cao and Hwa. A comparative analysis of experimental data with that of random data and VENUS data reveals erratic behavior of the multiplicity moments signifying chaotic multiparticle production in ultrarelativistic nuclear interactions.

We use the Skyrme-Hartree-Fock method, allowing all symmetries to be broken, to calculate the time-reversal-violating nuclear Schiff moment (which induces atomic electric dipole moments) in the octupole-deformed nucleus ${}^{225}\mathrm{Ra}.$ Our calculation includes several effects neglected in an earlier work, including self-consistency and polarization of the core by the last nucleon. We confirm that the Schiff moment is large compared to those of reflection-symmetric nuclei, though ours is generally a few times smaller than recent estimates.

We present a relativistic procedure for the chiral expansion of the two-pion exchange component of the $\mathrm{NN}$ potential, which emphasizes the role of intermediate $\pi N$ subamplitudes. The relationship between power counting in $\pi N$ and $\mathrm{NN}$ processes is discussed and results are expressed directly in terms of observable subthreshold coefficients. Interactions are determined by one- and two-loop diagrams, involving pions, nucleons, and other degrees of freedom, frozen into empirical subthreshold coefficients. The full evaluation of these diagrams produces amplitudes containing many different loop integrals. Their simplification by means of relations among these integrals leads to a set of intermediate results. Subsequent truncation to ${O(q}^4)$ yields the relativistic potential, which depends on six loop integrals, representing bubble, triangle, crossed box, and box diagrams. The bubble and triangle integrals are the same as in $\pi N$ scattering and we have shown that they also determine the chiral structures of box and crossed box integrals. Relativistic threshold effects make our results to be not equivalent with those of the heavy baryon approach. Performing a formal expansion of our results in inverse powers of the nucleon mass, even in regions where this expansion is not valid, we recover most of the standard heavy baryon results. The main differences are due to the Goldberger-Treiman discrepancy and terms of ${O(q}^3),$ possibly associated with the iteration of the one-pion exchange potential.

Performing a shell-model calculation for heavy nuclei has been a long-standing problem in nuclear physics. Here, we propose one possible solution. The central idea of this proposal is to combine the advantages of two existing models, the projected shell model (PSM) and the fermion dynamical symmetry Model (FDSM), to construct a multishell shell model. The PSM is an efficient method of coupling quasiparticle excitations to the high-spin rotational motion, whereas the FDSM contains a successful truncation scheme for the low-spin collective modes from the spherical to the well-deformed region. The new shell model is expected to describe simultaneously the single-particle and the low-lying collective excitations of all known types, yet keeping the model space tractable even for the heaviest nuclear systems.

$\gamma$-ray production cross sections have been measured for $\gamma$-ray lines copiously emitted in the ${}^3\mathrm{He}$ bombardment of ${}^{16}\mathrm{O}$ nuclei: the 937-, 1042-, and 1081-keV lines of ${}^{18}\mathrm{F}$ and the 1887-keV line of ${}^{18}\mathrm{Ne}.$ Four Ge detectors with BGO shielding for Compton suppression were used to measure the angular distributions of the $\gamma$ rays. The excitation functions have been obtained for ${}^3\mathrm{He}$ bombarding energies from 3.7 to 36 MeV. Total cross sections are tabulated for calculations relevant to $\gamma$-ray astronomy. The importance of these lines as diagnosis for the presence and properties of accelerated ${}^3\mathrm{He}$ in solar flares is discussed in light of the measured cross sections.

Charge-symmetry breaking in the nucleon-nucleon force is investigated within an effective field theory, using a classification of isospin-violating interactions based on power-counting arguments. The relevant charge-symmetry-breaking interactions corresponding to the first two orders in the power counting are discussed, including their effects on the ${}^3\mathrm{He}{-}^3\mathrm{H}$ binding-energy difference. The static charge-symmetry-breaking potential linear in the nucleon-mass difference is constructed using chiral perturbation theory. Explicit formulas in momentum and configuration spaces are presented. The present work completes previously obtained results.

States in ${}^{90}\mathrm{Zr}$ have been observed with the ${(n,n}^{\prime }\gamma )$ reaction using both spallation and monoenergetic accelerator-produced neutrons. A scheme comprised of 81 levels and 157 transitions was constructed concentrating on levels below 5.6 MeV in excitation energy. Spins have been determined by considering data from all experimental studies performed for ${}^{90}\mathrm{Zr}.$ Lifetimes have been deduced using the Doppler-shift attenuation method for many of the states, and transition rates have been obtained. A spherical shell-model interpretation in terms of particle-hole excitations assuming a ${}^{88}\mathrm{Sr}$ closed core is given. In some cases, enhancements in $B\left(M1\mathrm{}\right)\mathrm{}$ and $B\left(E2\mathrm{}\right)\mathrm{}$ values are observed that cannot be explained by assuming simple particle-hole excitations. Shell-model calculations using an extended $\mathrm{fpg}$-shell-model space reproduce the spectrum of excited states very well, and the gross features of the $B\left(M1\mathrm{}\right)\mathrm{}$ and $B\left(E2\mathrm{}\right)\mathrm{}$ transition rates. Transition rates for individual levels show discrepancies between calculations and experimental values.

We previously found that a cluster model reproduces satisfactorily the properties of normal deformed (ND) ground state and superdeformed (SD) excited bands in a wide range of even-even nuclei. We show here that the fractional change of the transition energies in two bands described by similar core-cluster configurations is closely related to the fractional change in the corresponding reduced masses. We compare our predictions to data on ground state ND bands for a series of light rare-earth and actinide isotopes, and on SD bands in the $A\sim 150$ and 190 regions. The model strongly suggests the existence of similar excited SD bands in ${}^{212}\mathrm{Pb}$ and ${}^{212}\mathrm{Po},$ in addition to the observed α-cluster-like ND ground state bands of these nuclei.

The process of proton emission from nuclei is studied by utilizing the two-potential approach of Gurvitz and Kalbermann in the context of the full many-body problem. A time-dependent approach is used for calculating the decay width. Starting from an initial many-body quasistationary state, we employ the Feshbach projection operator approach and reduce the formalism to an effective one-body problem. We show that the decay width can be expressed in terms of a one-body matrix element multiplied by a normalization factor. We demonstrate that the traditional interpretation of this normalization as the square root of a spectroscopic factor is only valid for one particular choice of projection operator. This causes no problem for the calculation of the decay width in a consistent microscopic approach, but it leads to ambiguities in the interpretation of experimental results. In particular, spectroscopic factors extracted from a comparison of the measured decay width with a calculated single-particle width may be affected.

Excitation functions were measured for the reactions ${}^{72}\mathrm{Ge}(n,\alpha )$${}^{69}{\mathrm{Zn}}^{m,g},$ ${}^{69}\mathrm{Ga}{\mathrm{}(n,p)\mathrm{}}^{69}{\mathrm{Zn}}^{m,g},$ ${}^{70}\mathrm{Zn}{\mathrm{}(n,2n)\mathrm{}}^{69}{\mathrm{Zn}}^{m,g},$ ${}^{74}\mathrm{Ge}(n,\alpha {)}^{71}{\mathrm{Zn}}^{m,g},$ and ${}^{71}\mathrm{Ga}{\mathrm{}(n,p)\mathrm{}}^{71}{\mathrm{Zn}}^{m,g}$ over the neutron energy range of 6.3–12.4 MeV. Quasimonoenergetic neutrons in this energy range were produced via the ${}^2\mathrm{H}{\mathrm{}(d,n)\mathrm{}}^3\mathrm{He}$ reaction using a deuterium gas target at the Jülich variable energy compact cyclotron. Use was made of the activation technique in combination with high-resolution HPGe-detector γ-ray spectroscopy. In a few cases low-level ${\beta }^{-}$counting was also applied. In order to decrease the interfering activities in those cases, either radiochemical separations were performed or isotopically enriched targets were used. For most of the reactions, the present measurements provide the first consistent sets of data near their thresholds. From the available experimental data, isomeric cross-section ratios were determined for the isomeric pair ${}^{69}{\mathrm{Zn}}^{m,g}$ in $(n,\alpha ),$ $\mathrm{}(n,p),$ and $\mathrm{}(n,2n)\mathrm{}$ reactions, and for the pair ${}^{71}{\mathrm{Zn}}^{m,g}$ in $(n,\alpha )$ and $\mathrm{}(n,p)\mathrm{}$ reactions. Nuclear model calculations using the code STAPRE, which employs the Hauser-Feshbach (statistical model) and exciton model (precompound effects) formalisms, were undertaken to describe the formation of both isomeric and ground states of the products. The calculational results on the total $(n,\alpha ),$ $\mathrm{}(n,p),$ and $\mathrm{}(n,2n)\mathrm{}$ cross sections agree fairly well with the experimental data. The experimental isomeric cross-section ratios, however, are reproduced only approximately by the calculation. For both the isomeric pairs investigated, the isomeric cross-section ratio in the $\mathrm{}(n,p)\mathrm{}$ reaction is higher than in other reactions.

Energy spectra (double-differential cross sections) for proton, deuteron, triton, and α-particle production in fast neutron induced reactions on uranium are reported for several incident neutron energies between 25 and 65 MeV. The spectra were obtained at nine laboratory angles between $20°$ and $160°$ and extrapolated and interpolated to other ten angles suitably covering the laboratory angular domain of $0°$ to $180°.$ The experimental setup and procedures for data reduction including corrections and normalization are presented and discussed. Based on the obtained double-differential cross sections, energy-differential and total cross sections are deduced as well. Theoretical calculations are based on GNASH and TALYS nuclear reaction codes which integrate the optical model, direct, preequilibrium, fission, and statistical nuclear reaction models in one calculation scheme.

The scaling of the yields of heavy projectile residues from the reactions of $25\mathrm{M}\mathrm{e}\mathrm{V}/\mathrm{n}\mathrm{u}\mathrm{c}\mathrm{l}\mathrm{e}\mathrm{o}\mathrm{n}{\hspace{0.5em}}^{86}\mathrm{Kr}$ projectiles with ${}^{124}\mathrm{Sn},$ ${}^{112}\mathrm{Sn}$ and ${}^{64}\mathrm{Ni},$ ${}^{58}\mathrm{Ni}$ targets is studied. Isotopically resolved yield distributions of projectile fragments in the range $Z=10\mathrm{}–36$ from these reaction pairs were measured with the MARS recoil separator in the angular range $2.7°–5.4°.$ For these deep inelastic collisions, the velocities of the residues, monotonically decreasing with Z down to $Z\simeq 26–28,$ are employed to characterize the excitation energy. The ratios $R_{21}\mathrm{}(N,Z)\mathrm{}$ of the yields of a given fragment $\mathrm{}(N,Z)\mathrm{}$ from each pair of systems are found to exhibit isotopic scaling (isoscaling), namely, an exponential dependence on the fragment atomic number Z and neutron number N. The isoscaling is found to occur in the residue Z range corresponding to the maximum observed excitation energies. The corresponding isoscaling parameters are $\alpha =0.43\mathrm{}$ and $\beta =-0.50$ for the $\mathrm{Kr}+\mathrm{Sn}$ system and $\alpha =0.27\mathrm{}$ and $\beta =-0.34$ for the $\mathrm{Kr}+\mathrm{Ni}$ system. For the $\mathrm{Kr}+\mathrm{Sn}$ system, for which the experimental angular acceptance range lies inside the grazing angle, isoscaling was found to occur for $Z<~26$ and $N<~34.$ For heavier fragments from $\mathrm{Kr}+\mathrm{Sn},$ the parameters vary monotonically, $\alpha$ decreasing with Z and $\beta$ increasing with N. This variation is found to be related to the evolution towards isospin equilibration and, as such, it can serve as a tracer of the $N/Z$ equilibration process. The present heavy-residue data extend the observation of isotopic scaling from the intermediate mass fragment region to the heavy-residue region. Interestingly, such high-resolution mass spectrometric data can provide important information on the role of isospin and isospin equilibration in peripheral and midperipheral collisions, complementary to that accessible from modern large-acceptance multidetector devices.

We report on the spin-dependent neutron scattering length on ${}^3\mathrm{He}$ from a microscopic calculation of $p{-}^3\mathrm{H},$ $n{-}^3\mathrm{He},$ and $d{-}^2\mathrm{H}$ scattering employing the Argonne $v_{18}$ nucleon-nucleon potential with and without additional three-nucleon force. The results of a comprehensive R-matrix analysis are compared to that of a recent measurement. The overall agreement for the scattering lengths is quite good. The imaginary parts of the scattering lengths are very sensitive to the inclusion of three-nucleon forces, whereas the real parts are almost insensitive.