We have investigated the phase transition and disoriented chiral condensate domain formation in linear $\sigma$ model. Solving the Langevin equation for the linear $\sigma$ model, we have shown that, for zero mass pions, the $\sigma$-model fields undergo a phase transition above a certain temperature ${(T}_c).\mathrm{}$ For finite mass pions, there is no phase transition. It was also shown that for zero mass pions, $\sigma$-model fields, thermalized at a temperature above $T_c,$ when cooled down rapidly, disoriented chiral condensate domains are formed, quite late in the evolution. For massive pions, no large disoriented chiral condensate domain is formed.

The cross section for $J/\psi$ absorption by nucleons is studied using a gauged SU(4) hadronic Lagrangian but with empirical particle masses, which has been used previously to study the cross sections for $J/\psi$ absorption by pion and $\rho$ meson. Including both two-body and three-body final states, we find that with a cutoff parameter of 1 GeV at interaction vertices involving charm hadrons, the $J/\psi -N$ absorption cross section is at most 5 mb and is consistent with that extracted from $J/\psi$ production from both photonuclear and proton-nucleus reactions.

The G-parity irregular induced tensor form factor in the weak nucleon axial vector current has been precisely determined by measuring the alignment correlation terms in the $\beta$-ray angular distributions of the purely spin aligned mirror pair ${}^{12}\mathrm{B}{(I}^{\pi }{=1\mathrm{}}^{+},$ $T_{1/2}=20.2\mathrm{}$ ms) and ${}^{12}\mathrm{N}{(I}^{\pi }{=1\mathrm{}}^{+},$ $T_{1/2}=11.0\mathrm{}$ ms) in order to place a new limit on the applicability of the G-parity conservation law. The coefficient of the induced tensor term was determined to be ${2Mf}_T{/f}_A=-0.21\pm 0.09$ (stat.) ±0.07 (syst.)±0.05 (theory) at a 90% confidence level. The previously obtained data in the year 1996 was reanalyzed to be added to the present result. The combined result is ${2Mf}_T{/f}_A=-0.15\pm 0.12\pm 0.05$ (theory) at a 90% confidence level. The obtained induced tensor coefficient is vanishingly small and is consistent with the theoretical prediction based on QCD in the framework of which the induced tensor form factor is proportional to the mass difference between up and down quarks. Also we set constraints on the Kubodera-Delorme-Rho parameters from the present result together with the results of correlation-type experiments in the mass $A=8\mathrm{}$ and 20 systems as $\zeta =-(0.12\mathrm{}\pm 0.14)\times {10}^{-3}\hspace{0.5em}{\mathrm{MeV}}^{-1}$ and $\lambda =+(0.30\mathrm{}\pm 0.88)\times {10}^{-3}$ in the $1\sigma$ level.

States near the ${}^{22}\mathrm{Ne}+p$ threshold in ${}^{23}\mathrm{Na}$ were investigated using the ${}^{22}\mathrm{Ne}{(}^3\mathrm{He}{,d)}^{23}\mathrm{Na}$ reaction over the angular range of $5°<~{\theta }_{\mathrm{lab}}<~35°$ at ${E(}^3\mathrm{He})=20\mathrm{}\hspace{0.5em}\mathrm{MeV}.$ Spectroscopic factors were extracted for states corresponding to resonances in the ${}^{22}\mathrm{Ne}(p,\gamma {)}^{23}\mathrm{Na}$ reaction. Two previously suggested resonances at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=68\mathrm{}$ and 100 keV were not observed at any angle. A new rate for the ${}^{22}\mathrm{Ne}(p,\gamma {)}^{23}\mathrm{Na}$ reaction has been calculated and its implications are discussed.

We use a simple gas model to study nonequilibrium aspects of the multiparticle dynamics relevant to heavy ion collisions. By performing numerical simulations for various initial conditions, we identify several characteristic features of the fast dynamics occurring in implosion-explosion-like processes.

We carry out an interacting boson model study of the Ru isotopes using a U(5)-SO(6) transitional Hamiltonian with fixed parameters, where the variation is due only to the change in boson number N. Transitional behavior in ${}^{104}\mathrm{Ru}$ is compared with recent predictions of an E(5) critical symmetry, including a modified version with an alternative $\beta$ dependence for the $T^{\left(\mathrm{E}2\right)}$ operator.

Recently reported measurements of fusion for the ${}^{6,7}\mathrm{Li}{+}^{16}\mathrm{O},{}^{13}\mathrm{C},$ and ${}^{12}\mathrm{C}$ systems using the characteristic $\gamma$-ray yield method were significantly larger than previous measurements for the same systems using the evaporation residue technique. The question of which set of measurements more accurately represents fusion and, indeed, the precise definition of what constitutes fusion is an important one, considering the recent interest in the question of whether fusion is inhibited or enhanced for weakly bound exotic nuclei such as ${}^6\mathrm{He}$ and ${}^{11}\mathrm{Li}.$ We present here fusion cross sections derived from continuum discretized coupled channels (CDCC) calculations using the barrier penetration model (BPM) that agree very well with the characteristic $\gamma$-ray method results.

An unfolding method is proposed to extract ground-state nuclear matter densities from heavy-ion elastic scattering data analyses at low (sub-barrier) and intermediate energies. The consistency of the results is fully checked. The method should be of value in determining densities for exotic nuclei.

Total and differential cross sections from literature, on the production of $K^{+}$-mesons in pA interactions at projectile energies between $T_p=0.8\mathrm{}$ and 2.9 GeV, covering the transition across the free nucleon-nucleon threshold at 1.58 GeV, have been investigated. From the target-mass dependence of the production cross sections no evidence for the expected change of the dominant reaction mechanism from two step to direct kaon production was found. At $T_p=1.0\mathrm{}\mathrm{GeV}$ the A dependences of the total cross sections and of the most recent data from COSY-Jülich, differential cross sections measured under forward angles, are strongly different. The invariant $K^{+}$-production cross sections show an overall exponential scaling behavior with the squared four-momentum transfer between the beam proton and the produced $K^{+}$ meson for $t<\mathrm{}-0.05{\mathrm{GeV}}^2,$ independent of the beam energy and emission angle. The data from COSY-Jülich reveal a strongly different t dependence in the region of $t>\mathrm{}0\mathrm{}{\mathrm{GeV}}^2.$ Further data at forward angles and different beam energies should be taken in order to explore this region of kinematically extreme conditions.

We discuss processes leading to two photon final states in peripheral heavy ion collisions at RHIC. Due to the large photon luminosity we show that the continuum subprocess $\gamma \gamma \to \gamma \gamma$ can be observed with a large number of events. We study this reaction when it is intermediated by a resonance made of quarks or gluons and discuss its interplay with the continuum process, verifying that in several cases the resonant process overwhelms the continuum one. It also investigated the possibility of observing a scalar resonance (the $\sigma$ meson) in this process. Assuming for the $\sigma$ the mass and total decay width values recently reported by the E791 Collaboration we show that RHIC may detect this particle in its two photon decay mode if its partial photonic decay width is of the order of the ones discussed in the literature.

The photoproduction $p\left(\gamma {,K}^{+}\right)\Lambda$ process is studied within a field-theoretic approach. It is shown that the background contributions constitute an important part of the reaction dynamics. We compare predictions obtained with three plausible techniques for dealing with these background contributions. It appears that the extracted resonance parameters drastically depend on the applied technique. We investigate the implications of the corrections to the functional form of the hadronic form factor in the contact term, recently suggested by Davidson and Workman [Phys. Rev. C 63, 025210 (2001)]. The role of background contributions and hadronic form factors for the identification of the quantum numbers of “missing” resonances is discussed.

The photoproduction of nucleon resonances is calculated based on a chiral constituent quark model including both relativistic corrections $H_{\mathrm{rel}}$ and two-body exchange currents, and it is shown that these effects play an important role. We also calculate the first moment of the nucleon spin structure function $g_1{(x,Q}^2)$ in the resonance region, and obtain a sign-changing point around $Q^2\sim 0.27\hspace{0.5em}{\mathrm{GeV}}^2$ for the proton.

The nuclear magnetic moment of the ${}^{143}\mathrm{Ce}$ ground state ${(T}_{1/2}=33.0\mathrm{}\hspace{0.5em}\mathrm{h},I^{\pi }{=3/2\mathrm{}}^{-})$ has been measured with the technique of nuclear magnetic resonance on oriented nuclei (NMR-ON) at low temperature. A sample ${(}^{143}\mathrm{Ce}Fe)$ was prepared by implanting into an Fe foil nuclei of mass number 143, which were separated from fission products with an on-line isotope separator. The NMR-ON spectra were obtained by detecting specific $\beta$ and $\gamma$ rays, and the resonance frequency was thereby determined to be 84.3(1) MHz. Using the reported value of the hyperfine magnetic field at other Ce nuclei in Fe, the nuclear magnetic moment of the ${}^{143}\mathrm{Ce}$ ground state was determined to be $|\mu |=0.43\mathrm{}\left(1\right)\mathrm{}\hspace{0.5em}{\mu }_N.$ This value is discussed based on a systematics of the magnetic moments of other $N=85\mathrm{}$ nuclei.

Employing NEXUS, one of the most recent simulation programs for heavy ion collisions, we investigate in detail the Hanbury Brown–Twiss correlation function of charged pions and kaons for central reactions 158-A GeV $\mathrm{P}\mathrm{b}+\mathrm{P}\mathrm{b}.$ For this study we supplement the standard simulation program by electromagnetic interactions. We find a wide distribution of freeze-out times which corresponds to a broad distribution of source sizes. Strong space-momentum space correlations as well as the electromagnetic interaction between the correlated pairs and the environment, which is of the same size as that between the hadrons of the correlated pair, strongly modify the correlation function. It can still be well parametrized by $C\left(\mathbf{k}\right)=1+\lambda e^{-4{\mathbf{k}}^2{R}^2},$ where k is the relative momentum. R, however, is not a simple function of the source radius; the complicated space-time structure of the source as well as the space-momentum space correlations and the final-state Coulomb interactions are encoded. The true source radius, as given by the rms radius of the emission points, and R differ by up to 30%.

The elastic scattering of protons on ${}^7\mathrm{Be}$ has been measured in the energy region from 1–3.3 MeV via the thick-target technique. The data conclusively demonstrate the existence of a $2^{-}$ state at an excitation energy of approximately 3.5 MeV in ${}^8\mathrm{B},$ and rule out a predicted $1^{+}$ state near 1.4 MeV. The relevance of these results for the ${}^7\mathrm{Be}$ $(p,\gamma )$ reaction, of interest in solar neutrino physics, is discussed.

A study of inelastic scattering of polarized $3.73-\mathrm{GeV}/c$ deuterons on protons in the energy region of the Roper $N\left(1440\right)\mathrm{}$ and the $\Delta \mathrm{}\left(1232\right)\mathrm{}$ resonances excitation has been performed in an exclusive experiment at LNS (Laboratoire National SATURNE, Saclay, France) using the SPES4-$\pi$ setup. Tensor and vector analyzing powers of pion production for the reactions: $d+\overrightarrow{p}d+n+{\pi }^{+},$ $d+\overrightarrow{p}d+p+{\pi }^0,$ $d+\overrightarrow{p}d+N+\pi \pi$ have been measured as functions of the squared deuteron four-momentum transfer t, of the effective mass of the subsystems $N\pi ,$ $N\pi \pi ,$ and of the pion emission angle. A strong dependence of these analyzing powers upon the pion emission angle is observed. It is found that $A_{\mathrm{yy}}$ values for the considered reaction channels are systematically larger than the known inclusive ${p(d,d}^{\prime })X$ world data at the nearest beam energy.

Coplanar and noncoplanar $\mathrm{np}\gamma$ cross sections and coplanar $\mathrm{np}\gamma$ analyzing powers are calculated in the energy region between 130 and 200 MeV for various nucleon scattering angles. Both pseudoscalar and pseudovector $\pi N$ couplings have been considered in our calculations. The results are used to investigate noncoplanarity effects. Agreement with available $\mathrm{np}\gamma$ data is good for most cases, but discrepancies do exist for some data points. We show that the dependence of the noncoplanar cross sections upon the noncoplanarity angle is significantly different at different photon angles. This suggests that this more general approach should be used to investigate the important noncoplanarity effects. Similar to what has previously been observed in potential-model calculations, the meson-exchange effects dominate the $\mathrm{np}\gamma$ process. To the best of our knowledge, results for $\mathrm{np}\gamma$ analyzing powers have heretofore not been calculated. As far as we know, no $\mathrm{np}\gamma$ analyzing power experimental data are presently available for comparison, but these results should prove useful for future experiments. The differences in either cross sections or analyzing powers calculated using the two couplings are very small for all cases studied, in contradistinction to our previous calculations for the $\mathrm{pp}\gamma$ process where the differences were found to be greater.

Within the supersymmetry scheme including many-body interactions, identical superdeformed (SD) bands and $\Delta I=4\mathrm{}$ bifurcation in $A\sim 130$ mass region are investigated systematically. Quantitatively good results for the $\gamma$-ray energy ${(E}_{\gamma })$ spectra, dynamical moments of inertia, and energy differences $\Delta E_{\gamma }-\Delta E_{\gamma }^{\mathrm{ref}}$ are obtained. This shows that the supersymmetry approach is quite powerful in describing not only generic rotational properties, but also $\Delta I=4\mathrm{}$ bifurcation and identical SD bands simultaneously. Meanwhile, the $\Delta I=4\mathrm{}$ bifurcation may come from the perturbation with SO(5) [or SU(5)] symmetry on the rotational symmetry.

The Hartree-Fock-Bogoliubov (HFB) equations in coordinate representation are solved exactly, i.e., with correct asymptotic boundary conditions for the continuous spectrum. The calculations are performed with effective Skyrme interactions. The exact HFB solutions are compared with HFB calculations based on box boundary conditions and with resonant continuum Hartree-Fock-BCS (HF-BCS) results. The comparison is done for the neutron-rich Ni isotopes. It is shown that close to the drip line the amount of pairing correlations depends on how the continuum coupling is treated. On the other hand, the resonant continuum HF-BCS results are generally close to those of HFB even in neutron-rich nuclei.

We have studied equilibration with respect to isospin degree of freedom in four 96 mass systems ${}^{96}\mathrm{Ru}{+}^{96}\mathrm{Ru},$ ${}^{96}\mathrm{Ru}{+}^{96}\mathrm{Zr},$ ${}^{96}\mathrm{Zr}{+}^{96}\mathrm{Ru},$ and ${}^{96}\mathrm{Zr}{+}^{96}\mathrm{Zr}$ at 100A MeV and 400A MeV with isospin-dependent quantum molecular dynamics. We propose that the neutron-proton differential rapidity distribution is a sensitive probe to the degree of equilibration with respect to the isospin degree of freedom. By analyzing the average $N/Z$ ratio of emitted nucleons, light charged particles, and intermediate mass fragments (IMF), it is found that there exist memory effect in multifragmentation process. The average $N/Z$ ratio of IMF reduces largely as beam energy increases from 100A MeV to 400A MeV that may result from the change of the behavior of the isotope distribution of IMF charges. The isotope distribution of IMF charges does also show certain memory effect at 100A MeV case but not at 400A MeV case.