The elastic and inelastic scattering cross sections of 28.0 MeV protons on ${}^{56}\mathrm{Fe}$ are measured. The results are analyzed in the framework of the coupled channels formalism. The nucleus ${}^{56}\mathrm{Fe}$ has been described in the literature to be soft regarding vibrational as well as asymmetric rotational motion. The analysis has therefore been done in terms of two collective models, i.e., the harmonic vibrational model and the asymmetric rotor model. In the vibrational model it was necessary to include the one-phonon components in the wave functions of the two-phonon $2^{+}$ and $4^{+}$ states while in the asymmetric rotor model the contributions due to the higher multipole moments $({\beta }_{40},{\beta }_{42})$ were found to be significant in the excitation of the $4_1^{+}$ and $4_2^{+}$ states.

We report measurements from experiment E864 at the BNL-AGS of the yields of particle unstable light nuclei in central collisions of ${}^{197}\mathrm{Au}$ with beam momentum of $11.5A$ $\mathrm{GeV}/c$ on ${}^{197}\mathrm{Pt}.$ Yields are reported as a function of rapidity for the nuclei ${}^4\mathrm{H},$ ${}^4\mathrm{Li},$ ${}^5\mathrm{He},$ and ${}^5\mathrm{Li}$ in the rapidity range from $y_{\mathrm{c}.\mathrm{m}.\mathrm{}}$ to $y_{\mathrm{c}.\mathrm{m}.\mathrm{}}+0.8\mathrm{}$ and in the transverse momentum range of approximately $0.1<~p_T/A<~0.4\mathrm{GeV}/c.\mathrm{}$ The yields are compared to previously reported yields and trends for the production of stable light nuclei. The nonobservation of two excited states ${}^5{\mathrm{He}}_{16.75\mathrm{MeV}}^{*}$ and ${}^5{\mathrm{Li}}_{16.66\mathrm{MeV}}^{*}$ is used to set an upper limit on the yields of these states.

The baryon-baryon interaction for the complete baryon octet is investigated in a unified framework of the resonating-group method which employs the spin-flavor ${\mathrm{SU}}_6$ wave functions with explicit color degrees of freedom. The interaction Hamiltonian is composed of the phenomenological confinement potential, the color Fermi-Breit interaction with explicit flavor symmetry breaking, and the effective meson-exchange potentials of scalar, pseudoscalar, and vector-meson types, acting between quarks. For the scalar- and vector-meson exchanges, the momentum-dependent higher-order terms are incorporated to reduce the attractive effect of the central interaction at higher energies. The single-particle potentials of the octet baryons, predicted by the G-matrix calculation, now have proper repulsive behavior in the momentum region $q_1=5\mathrm{}–20\hspace{0.5em}{\mathrm{fm}}^{-1}.$ A moderate contribution of the spin-orbit interaction from the scalar-meson exchange is also included. As to the vector mesons, a dominant contribution is the quadratic spin-orbit force generated from the $\rho$-meson exchange. This paper discusses the nucleon-nucleon interaction up to $T_{\mathrm{lab}}=800\mathrm{}\hspace{0.5em}\mathrm{MeV}.$ The nucleon-nucleon phase shifts at the nonrelativistic energies up to $T_{\mathrm{lab}}=350\mathrm{}\hspace{0.5em}\mathrm{MeV}$ are greatly improved, and now have attained the accuracy almost comparable to that of one-boson-exchange potentials. The deuteron properties and the low-energy observables of the nucleon-nucleon interaction are examined in the particle basis by incorporating the isospin symmetry breaking through the mass difference of the neutral and charged pions and the Coulomb effect as well. The nuclear saturation properties and the single-particle potential of the nucleon in symmetric nuclear matter are examined through the G-matrix calculation which uses the quark-exchange kernel directly.

We present a phenomenological study of three models with different effective degrees of freedom: a Goldstone boson exchange model which is based on quark-meson couplings, the quark delocalization, color screening model which is based on quark-gluon couplings with delocalized quark wave functions, and the Fujiwara-Nijmegen mixed model which includes both quark-meson and quark-gluon couplings. We find that for roughly two-thirds of 64 states consisting of pairs of octet and decuplet baryons, the three models predict similar effective baryon-baryon interactions. This suggests that the three very different models, based on different effective degrees of freedom, are nonetheless all compatible with respect to baryon spectra and baryon-baryon interactions. We also discuss the differences between the three models and their separate characteristics.

Realistic nuclear interactions based on the exchange of mesons are used to investigate pairing properties of symmetric nuclear matter in the framework of a relativistic field theory. For the pairing gap at the Fermi surface we find good agreement with earlier nonrelativistic descriptions based on phenomenological density dependent interactions of Gogny. The differences at large densities are traced back to the different behavior of these forces at short distances. The wave function of the Cooper pair as well as the contributions of the various parts of the interactions to the pairing field are investigated.

We present an update of the one-meson-exchange (OME) results for the weak decay of s- and p-shell hypernuclei [A. Parreño, A. Ramos, and C. Bennhold, Phys. Rev. C 56, 339 (1997)], paying special attention to the role played by final state interactions between the emitted nucleons. The present study also corrects for a mistake in the inclusion of the K and $K^{*}$ exchange mechanisms, which substantially increases the ratio of neutron-induced to proton-induced transitions ${\Gamma }_n/{\Gamma }_p.$ With the most up-to-date model ingredients, we find that the OME approach is able to describe very satisfactorily most of the measured observables, including the ratio ${\Gamma }_n/{\Gamma }_p.$

The strangeness-changing $(\Delta S=1)$ weak baryon-baryon interaction is studied through the nonmesonic weak decay (NMD) of double-Λ hypernuclei. Besides the usual nucleon-induced decay $\Lambda N\to \mathrm{NN}$ we discuss novel hyperon-induced decay modes $\Lambda \Lambda \to \Lambda N$ and $\Lambda \Lambda \to \Sigma N.\mathrm{}$ These reactions provide unique access to the exotic $\Lambda \Lambda K$ and $\Lambda \Sigma K$ vertices that place new constraints on chiral pertubation theory $\left(\chi \mathrm{PT}\right)\mathrm{}$ in the weak SU(3) sector. Within a meson-exchange framework, we use the pseudoscalar $\pi ,\eta ,K$ octet for the long-range part while parametrizing the short-range part through the vector mesons $\rho ,\omega {,K}^{*}.$ Realistic baryon-baryon forces for the $S=0,$ -1, and -2 sectors account for the strong interaction in the initial and final states. For ${}_{\Lambda \Lambda }^6\mathrm{He}$ the new hyperon-induced decay modes account for up to 4% of the total nonmesonic decay rate. Predictions are made for all possible nonmesonic decay modes.

We present a calculation of the cross section and the event generator of the reaction $\pi e\to \pi e\gamma .$ This reaction is sensitive to the pion generalized dipole polarizabilities, namely, the longitudinal electric ${\alpha }_L{(q}^2),$ the transverse electric ${\alpha }_T{(q}^2),$ and the magnetic $\beta {(q}^2)$ which, in the real-photon limit, reduce to the ordinary electric and magnetic polarizabilities $\overline{\alpha }$ and $\overline{\beta },$ respectively. The calculation of the cross section is done in the framework of chiral perturbation theory at $\mathcal{O}{(p}^4).\mathrm{}$ A pion virtual Compton scattering event generator has been written which is ready for implementation in GEANT simulation codes or for independent use.

Analyses of ${}^{248}\mathrm{Cm}$ fission product γ-ray coincidence data recorded at Gammasphere have yielded additional information about $\gamma$-ray cascades in $N=82\mathrm{}$ isotones ${}^{134}\mathrm{Te}$ and ${}^{135}\mathrm{I}.$ New-yrast and near-yrast states in both nuclei have been identified, and they are interpreted as specific shell model excitations.

Precise four-body calculations for ${}_{\Lambda }^4\mathrm{He}$ and ${}_{\Lambda }^4\mathrm{H}$ have been performed in the framework of a variational method employing Jacobi-coordinate Gaussian-basis functions. All of the $\mathrm{NNN}\Lambda$ and $\mathrm{NNN}\Sigma$ rearrangements are explicitly taken into account for the first time in the context of realistic $\mathrm{NN}$ and $\mathrm{YN}$ interactions. The role of $\Lambda -\Sigma$ conversion and the size of the virtual $\Sigma$ component in ${}_{\Lambda }^4\mathrm{He}$ and ${}_{\Lambda }^4\mathrm{H}$ are discussed.

The fusion excitation functions of ${}^{40,48}\mathrm{Ca}{+}^{48}\mathrm{Ca}$ have been measured near and below the Coulomb barrier and the fusion barrier distributions have been extracted from the data. The cross sections for ${}^{48}\mathrm{Ca}{+}^{48}\mathrm{Ca}$ are well reproduced by coupled-channels (CC) calculations, including inelastic excitations to the $2^{+}$ and $3^{-}$ states of both nuclei and using a standard potential. The cross sections of ${}^{40}\mathrm{Ca}{+}^{48}\mathrm{Ca}$ are significantly larger than previous data for the same system, especially near and above the barrier. While a much better agreement between present data and CC calculations is found in that energy range, the sub-barrier cross sections are still underpredicted.

The pseudorapidity dependence of elliptic flow in Au+Au collisions at $130A\hspace{0.5em}\mathrm{GeV}$ is studied within a full three-dimensional hydrodynamic model in the light-cone coordinate. First, we prepare two initial conditions in the hydrodynamic model for analyzing elliptic flow. Both initial conditions lead to reasonable agreement with single particle spectra in central and semicentral collisions. Second, by using these hydrodynamic simulations, we compare elliptic flow as a function of pseudorapidity with experimental data recently measured by the PHOBOS Collaboration. Our results are in agreement with experimental data only near midrapidity. This suggests that thermalization in the early stage of collisions is not achieved in forward and backward rapidity regions.

Using the soft-photon approximation, we address the issue of the importance of noncoplanarity effects in proton-proton bremsstrahlung. We investigate the noncoplanar cross section as a function of the noncoplanarity angle $\overline{\phi }$ for the entire range of the photon polar angle ${\psi }_{\gamma }.$ The $\overline{\phi }$ dependence is shown to provide a significant variation in the cross section, for a given ${\psi }_{\gamma }.$ Thus, there can be some uncertainty in determining experimental coplanar cross sections. To avoid the phase-space singularities of spherical geometry, we utilize the Harvard noncoplanar geometry. A detailed explication of the Harvard geometry is provided. Comparison of our calculations with experimental data is included.

High-spin states in ${}^{180}\mathrm{Ir}$ have been investigated by means of in-beam $\gamma$-ray spectroscopy techniques with the ${}^{154}\mathrm{Sm}{(}^{31}\mathrm{P},5n\gamma {)}^{180}\mathrm{Ir}$ reaction. Excitation functions, $x-\gamma$ and $\gamma -\gamma -t$ coincidences, DCO (directional correlation of $\gamma$ rays deexciting oriented states) ratios, and intraband $B\left(M1\mathrm{}\right)/B\left(E2\mathrm{}\right)\mathrm{}$ ratios were measured. Five rotational bands have been identified and their configurations are proposed on the basis of $B\left(M1\mathrm{}\right)/B\left(E2\mathrm{}\right)\mathrm{}$ ratios and by comparing the band properties with known bands in neighboring odd-mass and even-mass nuclei. The neutron $\mathrm{AB}$ crossing is observed at $ħ{\omega }_c=0.26\mathrm{}\left(1\right)\mathrm{}\hspace{0.5em}\mathrm{MeV}$ for the $\pi {1/2}^{-}\left[541\right]\otimes \nu {1/2}^{-}\left[521\right]$ and $\pi {1/2}^{-}\left[541\right]\otimes \nu {5/2}^{-}\left[512\right]$ bands, respectively. Staggering of levels as a function of the number of neutron pairs is revealed in the $\pi {1/2}^{-}\left[541\right]\otimes \nu {1/2}^{-}\left[521\right]$ doubly decoupled bands of ${}^{178–186}\mathrm{Ir}.$ The gradual alignment gains at low rotational frequencies are observed in the two strongly coupled bands. Band crossings and alignments in ${}^{180}\mathrm{Ir}$ are discussed with reference to the total Routhian surface and cranked shell model calculations performed for the neighboring odd-mass nuclei.

An in-beam study of excited states in the transfermium nucleus ${}^{252}\mathrm{No}$ has been performed using the recoil separator RITU together with the JUROSPHERE II array at the University of Jyväskylä. This is the second transfermium nucleus studied in an in-beam experiment. Levels up to spin 20 were populated and compared to levels in ${}^{254}\mathrm{No}.$ An upbend is seen at a frequency of 200 keV/ħ corresponding to spin 16. We also use an improved systematics to connect the energy of the lowest $2^{+}$ state with its half-life and find that the deformation of both ${}^{252,254}\mathrm{No}$ is slightly larger than previously assumed.

Cross sections of the ${}^{51}\mathrm{V}{\mathrm{}(n,p)\mathrm{}}^{51}\mathrm{Ti},$ ${}^{51}\mathrm{V}(n,\alpha {)}^{48}\mathrm{Sc},$ and ${}^{\mathrm{nat}}\mathrm{V}(n,x\alpha {)}^{47}\mathrm{Sc}$ reactions were measured in the energy range from 11.7 to 20.5 MeV. The measurements for the latter reaction establish for the first time a consistent excitation curve. The present data for the $\mathrm{}(n,p)\mathrm{}$ process connect the measurements around 14 MeV with the recent data set above 17 MeV. The shapes and magnitudes of the three excitation functions from the reaction thresholds up to 21 MeV, as well as the ones for the competing reaction channel ${}^{51}\mathrm{V}{\mathrm{}(n,2n)\mathrm{}}^{50}\mathrm{V},$ are described by model calculations using a consistent parameter set. The agreement between experimental and calculated data is, in general, good both at the maxima and at the tails of the excitation functions. In contrast to earlier studies, the major contribution to the ${}^{\mathrm{nat}}\mathrm{V}(n,x\alpha {)}^{47}\mathrm{Sc}$ cross section at 14.8 MeV incident energy is attributed to the ${}^{50}\mathrm{V}(n,\alpha {)}^{47}\mathrm{Sc}$ reaction; at energies above 15 MeV the ${}^{51}\mathrm{V}{(n,n}^{\prime }\alpha )$ process is dominant.

We have analyzed fragmentation processes of ${}^{197}\mathrm{Au}$ and ${}^{208}\mathrm{Pb}$ projectiles in reactions with targets ranging from ${\mathrm{CH}}_2$ to Pb at projectile energies between 1.0 and 158 GeV/nucleon. For these experiments we used stacks consisting of foils of the plastic nuclear track detector material ${\mathrm{C}\mathrm{R}-39(\mathrm{C}}_{12}{\mathrm{H}}_{18}{\mathrm{O}}_7).$ This detector material allows us to measure the charges and trajectories of relativistic particles with charges above a detection threshold $Z_t.$ In this paper we analyze target and projectile energy dependences of transverse momentum distributions for projectile fragments produced in different fragmentation processes such as spallation, fission, and multifragmentation. Furthermore, for multifragmentation processes multiplicity dependences of the transverse momenta were studied. We found that besides the statistically distributed Fermi momenta of the nucleons, Coulomb repulsion may significantly contribute to the transverse momenta of the fragment nuclei. For heavy target nuclei, contributions caused by the repulsion of the incoming projectile nucleus and also by the outgoing fragment nucleus have been observed. For fission-type reactions and for multifragmentation reactions, in which more than one heavy fragment is produced in an interaction, the mutual repulsion between the fragments contributes to the measured transverse momenta.

Two-fragment reduced-velocity correlation functions of intermediate-mass fragments emitted from midrapidity component and quasiprojectile (QP) sources formed in ${}^{58}\mathrm{Ni}{+}^{12}\mathrm{C}$ and ${}^{58}\mathrm{Ni}{+}^{197}\mathrm{Au}$ reactions at 34.5 MeV/nucleon have been studied. For the midrapidity component, they show a stronger Coulomb suppression at low relative velocities than for the QP source, suggesting a shorter emission time for it than for the QP source. Comparing the experimental correlation functions with the prediction of many-body Coulomb trajectory code, the emission times of a QP source formed in both reactions were extracted as a function of the excitation energy. The variation of emission time of the QP source with the excitation energy is independent of the reaction system. It decreases monotonically with the excitation energy in the range of $(2\mathrm{}–6)A$ MeV from several hundred $\mathrm{fm}/c$ to about $100\hspace{0.5em}\mathrm{fm}/c.\mathrm{}$ Above an excitation energy of $6A$ MeV, it becomes very short and saturates, suggesting that the QP source undergoes a multifragmentationlike breakup. The influence of the quasitarget fragment Coulomb interaction on QP emission time is also considered.

Many of the hadron-hadron cross sections required for the study of the dynamics of matter produced in relativistic heavy-ion collisions can be calculated using the quark-interchange model. Here we evaluate the low-energy dissociation cross sections of $J/\psi ,$ ${\psi }^{\prime },$ χ, ${\rm Y},$ and ${{\rm Y}}^{\prime }$ in collision with π, ρ, and K. These are important for the interpretation of heavy-quarkonium suppression as a signature for the quark gluon plasma, as such comover dissociation processes also contribute to heavy-quarkonium suppression, and must be understood and incorporated in simulations of heavy-ion collisions before QGP formation can be established through this signature.

Invariant multiplicity distributions of the leading neutron and proton have been measured in minimum bias $p+\mathrm{Be},$ $p+\mathrm{Al},$ $p+\mathrm{Cu},$ and $p+\mathrm{Pb}$ collisions at $19\hspace{0.5em}\mathrm{GeV}/c$ and $p+\mathrm{Be}$ and $p+\mathrm{Pb}$ collisions at $12\hspace{0.5em}\mathrm{GeV}/c$ with the E864/E941 spectrometer at the Alternating Gradient Synchrotron (AGS). The experimental acceptance for the measurement covers a rapidity region of $1.7<~y<~3.3$ and transverse momentum region of $0.075\hspace{0.5em}\mathrm{GeV}/c$ $<~p_T<~1.025\hspace{0.5em}\mathrm{GeV}/c.\mathrm{}$ The leading proton and leading neutron production, as a function of the light cone momentum fraction $x_{+},$ show energy scaling at AGS energies. The proton/neutron ratio, ${(dN/dx}_{+}{)}_p{/(dN/dx}_{+}{)}_n,$ decreases from about 5.0 near beam rapidity to about one at midrapidity. The ratio has no strong target dependence as a function of rapidity. The target dependence of the leading proton distribution as a function of $x_{+}$ demonstrates an approximate energy scaling from the AGS to the Super Proton Synchrotron.