The yrast and yrare lines are obtained for ${}^{40}\mathrm{Ca}$ using a statistical method by assuming the nucleons to move in a triaxially deformed Nilsson harmonic oscillator potential. The backbending and yrast traps are observed in the case of ${}^{40}\mathrm{Ca}$ at certain spins. A shift in the first yrast minima towards higher angular momentum states with an increase in entropy is observed. A second backbending is found to occur at spin $M=17\mathrm{}ħ$ for all entropies. The excitation energy, the nuclear level density, the single-particle level density parameter, and the spin cutoff parameter are determined as functions of temperature and angular momentum by minimizing the free energy. The Strutinsky method is used to study the variation of the shell correction with angular momentum for equilibrium shapes. The Fermi energies obtained as a function of angular momentum are used for calculating this shell correction. The nucleus is found to be spherical up to $M=6\mathrm{}ħ$ and becomes oblate with a further increase in angular momentum. The shell correction is found to increase with the deformation having a minimum value for the spherical shape.

Results are presented for the ${}^3$He$(\gamma ,{\pi }^{+}{\pi }^{-})$ reaction in the region 380 $<~E_{\gamma }<~700$ MeV, investigated with the use of a 10% duty factor tagged photon beam, in conjunction with the TAGX multiparticle spectrometer. The study of such multipion photoproduction reactions has motivated a number of chiral symmetric models, and is expected to provide an insight on the role of the $\Delta$ and $N^{*}$ resonances in the nuclear medium. From comparisons of the data with simple reaction simulations, it was found that the data were best fit with a combination of multibody phase space channels, quasifree $\Delta$ and $N^{*}$, and $\Delta \Delta$ production channels. The results are compared with other double pion photoproduction reactions on hydrogen and deuterium.

Measurements of inclusive ${(p,}^3$He) reactions on ${}^{59}$Co and ${}^{197}$Au at incident energies of 120, 160, and 200 MeV are compared with calculations based on a statistical multistep direct reaction theory. The angular range extends from $10°$ to $160°$ and emission energies exceeding 30 MeV were studied. It is found that the multistep contributions are dominant for all but the highest outgoing energies. This is in qualitative agreement with previous results for the inclusive $(p,\alpha )$ reaction at the same incident energies and targets.

Measurements were made of the doubly differential cross sections for three inclusive pion reactions on ${}^3$He: ${\pi }^{-}$ double charge exchange (DCX), and ${\pi }^{+}$ and ${\pi }^{-}$ inelastic scattering. The cross sections for DCX were measured at incident pion energies of 120, 180, and 240 MeV, and at angles of 25$°$, 50$°$, 80$°$, 105$°$, and 130$°$, while inelastic scattering cross sections were measured at 120, 180, and 240 MeV and scattering angles of 50$°$, 80$°$, 105$°$, and 130$°$. In each case the outgoing pion energy spectra were measured from 10 MeV up to the kinematic limit. The DCX spectra exhibit a double-peaked structure at forward angles that can be understood as a consequence of a sequential single charge exchange mechanism. Model calculations based on this mechanism are in rough agreement with the measured spectra. The doubly differential cross sections measured for the inelastic scattering reactions exhibit a prominent quasielastic peak. A distorted-wave impulse-approximation calculation of the quasielastic cross sections has been performed and a comparison made with the measurements.

The experimental signature of the formation of a necklike structure, with a velocity between that of the projectilelike emitter and that of the targetlike emitter, is investigated with the same beam and experimental setup for targets lighter and heavier than the projectile. The reactions are ${}^{35}$Cl on ${}^{12}$C and on ${}^{197}$Au at 43 MeV/nucleon. Particle velocity distributions are compared with two-source statistical simulations and the presence of a necklike structure is inferred from the data. In the second part of the paper, dynamical model simulations with the formation of a necklike structure are presented for the ${}^{35}$Cl+${}^{12}$C system at 43 MeV/nucleon.

A fine-step excitation function has been measured across the resonance reported at 32.5 MeV in the ${}^{12}\mathrm{C}{[}^{12}\mathrm{C}{,}^{12}\mathrm{C}{(0\mathrm{}}_2^{+}\left){]}^{12}\mathrm{C}{(0\mathrm{}}_2^{+}\right)$ reaction. Correlated structure is also observed in other exit channels involving the $0_2^{+}$ and $3_1^{-}$ states of ${}^{12}$C and in the ${}^{16}\mathrm{O}{+}^8\mathrm{Be}$ channel.

We have measured angular distributions and total cross sections for the reactions $\mathrm{}(d,p)\mathrm{}$ and $(d,\alpha )$ to all excited states with positive $Q$-values on the nuclei ${}^9$Be, ${}^{10}$B, and ${}^{11}$B between center of mass (c.m.) energies of 57 and 139 keV, 67 and 141 keV, and 76 and 144 keV, respectively, and the reaction $\mathrm{}(d,t)\mathrm{}$ on the nucleus ${}^9$Be to the ${}^8$Be ground state between c.m. energies of 57 and 139 keV. Astrophsyical $S$ factors for these reactions are derived from the total cross-section measurements. Some of the measured angular distributions are far from isotropic even at the lowest energies. This anisotropy is reproduced reasonably well by distorted-wave Born approximation calculations in which the distorting potentials are modified with an additional short-range term.

The systematics of fusion-evaporation reactions in the mass-symmetric system ${}^{40}\mathrm{Ar}{+}^{40}$Ca are studied for incident energies of 5–30 MeV/nucleon. The measurement of the resulting evaporation residues in coincidence with emitted neutrons permits a clear identification of central collisions and a separation of equilibrium and preequilibrium contributions. The total neutron multiplicities and the total average mass loss of the system both show a tendency of soft saturation. Above about 20 MeV/nucleon the increase of the energy removal is entirely due to preequilibrium emission of light particles. The total excitation energy of the evaporation residues approaches a maximum value, but the excitation energy per nucleon rises linearly without any sign of saturation. At even higher projectile energies the production of evaporation residues is dramatically reduced and they become indistinguishable from spectatorlike fragments resulting from less central collisions. Thus, the long-standing question of a limiting excitation energy in hot nuclei can probably not be solved by experimental studies of fusion-evaporation reactions.

Experimental data obtained with the 4$\pi$ multidetector system INDRA are used to study the light charged particle (LCP, $Z<~$2) and intermediate mass fragment (IMF, $Z>~$3) production in peripheral and semicentral collisions of Xe and Sn at 50 MeV/nucleon. It is found that a sizable fraction of the detected LCP’s and IMF’s originates from the midvelocity region. These fragments can be seen to come either from a prompt (preequilibrium) mechanism or from a slower but dynamically influenced emission process. The relative magnitude of the dynamically influenced emission relative to the isotropic statistical evaporation is presented as a function of the transverse energy of light particles, used as an impact parameter selector. The results are compared to dynamical models with which a good agreement is obtained.

Dynamical nucleation-growth models are applied to an interpretation of the shape of fragment size distributions observed in heavy-ion collisions. It is shown that by such a kinetic approach a more complete and accurate description of multifragmentation can be given compared with nondynamical treatments (e.g., percolation or Fisher’s droplet models). This way, nuclear multifragmentation can be understood as a particular case of self-organization in a highly excited nonequilibrium nucleonic system undergoing a first-order phase transition.

We investigate resonance states of the Morse plus centrifugal potential which has been used to explain the observed ${}^{12}$C+${}^{12}$C resonances by Satpathy et al. It is found that most of the enhancements in their calculated cross sections do not correspond to real resonances, but to so-called echoes. Furthermore, resonance poles of the Morse potential are searched exhaustively by the use of the complex scaling method. There are no resonance poles found in the higher energy region where many resonances are observed experimentally. We therefore conclude that the Morse potential is not appropriate for a comprehensive explanation of a series of resonances in the ${}^{12}$C+${}^{12}$C system.

We consider a composite spin-half particle moving in spatially varying scalar and vector fields. The vector field is assumed to couple to a conserved charge, but no assumption is made about either the structure of the composite or its coupling to the scalar field. A general form for the piece of the spin-orbit interaction of the composite with the scalar and vector fields which is first order in momentum transfer $\mathbf{Q}$ and second order in the fields is derived.

The charge symmetric scattering systems ${}^{12}{\mathrm{C}+}^{13}\mathrm{N}$ and ${}^{12}{\mathrm{C}+}^{13}\mathrm{C}$ have been investigated by using the orthogonalized coupled-reaction-channel (OCRC) method with the basis functions of the elastic, inelastic, and transfer channels defined by the single-particle states, $1p$$\frac{1}{2}$, $2s$$\frac{1}{2}$, $1d$$\frac{5}{2}$, and $1d$$\frac{3}{2}$ of the valence nucleon in ${}^{13}\mathrm{N}$ or ${}^{13}\mathrm{C}.$ The data of the elastic scattering of ${}^{13}\mathrm{N}$ on ${}^{12}\mathrm{C}$ measured by Liénard et al. have been explained consistently with the data of the elastic and inelastic scattering of the ${}^{12}{\mathrm{C}+}^{13}\mathrm{C}$ system. The CRC effects on both of the above systems are very strong, although those on the ${}^{12}{\mathrm{C}+}^{13}\mathrm{N}$ system are fairly weaker than the ${}^{12}{\mathrm{C}+}^{13}\mathrm{C}$ system. The role of the highly excited single-particle states $1d$$\frac{3}{2}$ is particularly important in the formation of a specific CRC scheme, i.e., the formation of the covalent molecules due to the hybridization caused by the mixing of the different parity single-particle states. The fusion cross sections of the ${}^{12}{\mathrm{C}+}^{13}\mathrm{C}$ system at energies below the Coulomb barrier are strongly enhanced as a result of the strong CRC effects as compared with those of the ${}^{12}{\mathrm{C}+}^{12}\mathrm{C}$ system, while in ${}^{12}{\mathrm{C}+}^{13}\mathrm{N}$ system the enhancement of the sub-barrier fusion has not been observed. The above absorption mechanism for the ${}^{12}{\mathrm{C}+}^{13}\mathrm{C}$ system explains the lack of the molecular-resonance phenomena observed in the ${}^{12}{\mathrm{C}+}^{12}\mathrm{C}$ system. We check the effects of the dipole $\mathrm{}\left(E1\mathrm{}\right)\mathrm{}$ transition of the valence nucleon in ${}^{13}\mathrm{N}$ (and also in ${}^{13}\mathrm{C}$) due to the core-core Coulomb interaction in the scattering at sub-barrier energies. The effects are not appreciable.

We calculate cross sections for coherent pion production in nuclei induced by neutrinos and antineutrinos of the electron and muon types. The analogies and differences between this process and the related ones of coherent pion production induced by photons or the $\mathrm{}(p,n)\mathrm{}$ and ${(}^3\mathrm{He},t)$ reactions are discussed. The process is one of the several ones occurring for intermediate energy neutrinos, to be considered when detecting atmospheric neutrinos. For this purpose the results shown here can be easily extrapolated to other energies and other nuclei.

We consider the single particle level density $g\left(\epsilon \right)$ of a realistic finite depth potential well, concentrating on the continuum $(\epsilon >0)$ region. We carry out quantum-mechanical calculations of the partial level density $g_l\left(\epsilon \right)$, associated with a well-defined orbital angular momentum $l<~40$, using the phase-shift derivative method and the Green’s-function method and compare the results with those obtained using the Thomas-Fermi approximation. We also numerically calculate $g\left(\epsilon \right)$ as a $l$ sum of $g_l\left(\epsilon \right)$ up to a certain value of ${\mathcal{l}}_{\max }<~40$ and determine the corresponding smooth level densities using the Strutinsky smoothing procedure. We demonstrate, in accordance with Levinson’s theorem, that the partial contribution $g_l\left(\epsilon \right)$ to the single particle level density from continuum states has positive and negative values. However, $g\left(\epsilon \right)$ is nonnegative. We also point out that this is not the case for an energy-dependent potential well.

A technique to deal with Coulomb electron distortions in the analysis of ${(e,e}^{\prime }p)$ reactions is presented. Thereby, no approximations are made. The suggested technique relies on a partial-wave expansion of the electron wave functions and a multipole decomposition of the electron and nuclear current in momentum space. In that way, we succeed in keeping the computational times within reasonable limits. This theoretical framework is used to calculate the quasielastic ${(e,e}^{\prime }p)$ reduced cross sections for proton knockout from the valence shells in ${}^{16}$O, ${}^{40}$Ca, ${}^{90}$Zr, and ${}^{208}$Pb. The final-state interaction of the ejected proton with the residual nucleus is treated within an optical potential model. The role of electron distortion on the extracted spectroscopic factors is discussed.

The proton and neutron decay of the giant monopole resonance in ${}^{90}$Zr is analyzed in terms of collective and statistical doorway states. For this purpose the hybrid model of the decay is used in the context of channel particle competition. The semidirect components are compatible with the particle-hole continuum random-phase-approximation calculations. The protons spectra are found to be predominantly statistical while the neutron spectra contain semidirect contributions.

The effects of the isotopic asymmetry of colliding nuclei and the Coulomb interactions are simultaneously considered for an equilibrated hadron gas produced in heavy-ion collisions. The asymmetry in the production of negative and positive pions which is manifested in the differences in the ${\pi }^{-}$ and ${\pi }^{+}$ multiplicities and in the shape of their momentum spectra is analyzed.

Considering massless $u$ and $d$ quarks, and massive $s$ quarks confined in a bag with the bag pressure constant $B^{1/4}=145\mathrm{}$ MeV, a grand canonical partition function with color-singlet restriction [singlet of SU(3) color gauge group] is constructed at finite temperature. Then the stability of finite size strangelets with the baryon number $A<~100$ is studied minimizing the free energy as a function of the radius of the bag. As expected, the color singletness has effects only at finite temperatures and its importance grows with the increase of temperature. Notably, the most pronounced shell structure (metastable state) at $A$=6 now vanishes only at $T>~$30 MeV as compared to $T$=20 MeV otherwise. The color-singletness restriction has significant effects on the structure of low mass $(A$≲$50)$ strangelets but becomes unimportant in the bulk limit.

We have used the event generator LUCIAE to analyze the data of singly strange particle production in $\mathrm{pp}$, $\mathrm{pA}$, and $\mathrm{AA}$ reactions at $200A$ GeV and compared them with the corresponding experimental data and theoretical results of HIJING, VENUS, and RQMD. The results indicate that for reproducing the NA35 data of $\mathrm{AA}$ reactions it requires a somewhat larger $s$ quark suppression factor $\mathrm{}(s=0.3\mathrm{})\mathrm{}$ and shorter formation time $(\tau =1\mathrm{}$ fm/$c)$ of produced particles than for reproducing the experimental data of $\mathrm{pp}$ and $\mathrm{pA}$ $(s=0.2\mathrm{}$ and $\tau =1.5\mathrm{}$ fm/$c)$. This might be understood intuitively from the relationship between the effective string tension and the violence of collision. However, the NA36 data of the negative multiplicity dependence of $\Lambda$ in S + Pb reaction at 200 A GeV could not be well reproduced by LUCIAE, VENUS, or RQMD, and the NA36 data prefers model parameters of $s=0.2\mathrm{}$ and $\tau =1.5\mathrm{}$ fm/$c$ especially, this seems hard to understand and needs further studies. From comparing the NA35 data of the rapidity distribution of $\Lambda$ in S + Ag reactions to the corresponding results of LUCIAE one knows that the effect of varying the $s$ quark suppression factor from 0.2 to 0.3 is smaller than the effect of rescattering with respect to strangeness production.