Statistical model calculations were performed to interpret the prompt fission neutron spectra (PFNS) from ${}^{238}\mathrm{U}\left(n,f\right)$ and ${}^{232}\mathrm{Th}\left(n,f\right)$ reactions for the incident neutron energies $E_n\sim 6–18\text{MeV}$. Spectra of the prefission (presaddle) $\left(n,xnf\right)$ reaction neutrons were calculated with Hauser-Feshbach statistical model, fission and $\left(n,xn\right)$ reaction cross section data being described consistently. Spectra of neutrons, evaporated from the fission fragments, were approximated as a sum of two Watt distributions. The reduced neutron velocity in the center-of-mass system due to the neutron emission during fragment acceleration was assumed. PFNS component due to presaddle neutrons is evidenced in the shape of the measured PFNS data. We show it to be strongly correlated with the emissive fission contributions to the observed fission cross sections. The dependence of these contributions on the target nuclide fissility and incident neutron energy is shown to be pronounced in the PFNS shapes for ${}^{232}\mathrm{Th}\left(n,f\right)$ and ${}^{238}\mathrm{U}\left(n,f\right)$ reactions. High-energy tails of the first neutrons of $\left(n,nf\right)$ and $\left(n,2nf\right)$ reactions are shown to be evidenced in the PFNS measured data trends.

The improved quantum molecular dynamics model is further developed by introducing new parameters in interaction potential energy functional based on Skyrme interaction of ${\text{SkM}}^{*}$ and SLy series. The properties of ground states of selected nuclei can be reproduced very well. The Coulomb barriers for a series of reaction systems are studied and compared with the results of the proximity potential. The fusion excitation functions for a series of fusion reactions are calculated and the results are in good agreement with experimental data.

The mass-number dependences of the high-energy pion single-charge-exchange reactions are studied under the distorted-wave impulse approximation. The observed forward-angle cross sections are approximately proportional to $(N-Z)\times A^{-\alpha \left(E\right)}$ for the isobaric-analog transition and the overall feature is explained in the present calculation. The coefficient $\alpha \left(E\right)$ is shown to be strongly dependent on the imaginary part of the optical potential. The observed monotonic decrease of the coefficient $\alpha \left(E\right)$ with respect to the incident energy is reproduced but the absolute values of $\alpha \left(E\right)$ are smaller than those of experiment. It is also shown that the coefficient $\alpha \left(E\right)$ is considerably influenced by the rms radii of the isovector density of the target nuclei.

The small sub-barrier tunneling probability of nuclear processes can be dramatically enhanced by collision with incident charged particles. Semiclassical methods of theory of complex trajectories have been applied to nuclear tunneling, and conditions for the effects have been obtained. We demonstrate the enhancement of $\alpha$ particle decay by incident proton with energy of about $0.25\text{MeV}$. We show that the general features of this process are common for other sub-barrier nuclear processes and can be applied to nuclear fission.

The isoscaling is investigated using the fragment yield data from fully reconstructed quasiprojectiles observed in peripheral collisions of ${}^{28}\mathrm{Si}$ with ${}^{124,112}\mathrm{Sn}$ at projectile energies 30 and $50\text{MeV}∕\text{nucleon}$. The excitation energy dependence of the isoscaling parameter ${\beta }^{\prime }$ is observed which is independent of beam energy. For a given quasiprojectile produced in reactions with different targets no isoscaling is observed. The isoscaling thus reflects the level of $N∕Z$ equilibration in reactions with different targets represented by the initial quasiprojectile samples. The excitation energy dependence of the isoscaling parameter ${\beta }^{\prime }$, corrected for the trivial $1∕T$ temperature dependence, does not follow the trend of the homogeneous system above $4\text{MeV}∕\text{nucleon}$ thus possibly signaling the onset of separation into isospin asymmetric dilute and isospin symmetric dense phase.

The cross section for electron scattering by nuclei at high momentum transfers is calculated within the Fermi smearing approximation, where binding effects on the struck nucleon are introduced via the relativistic Hartree approximation. The model naturally preserves current conservation, since the response tensor for an off-shell nucleon conserves the same form as for a free one but with an effective mass. Different parametrizations for the inelastic nucleon structure function are analyzed. The smearing at the Fermi surface is introduced through a momentum distribution obtained from a perturbative nuclear matter calculation. Recent CEBAF data on inclusive scattering of $4.05\text{GeV}$ electrons on ${}^{56}\mathrm{Fe}$ are well reproduced for all measured geometries for the first time, as is evident from the comparison with previous calculations.

We investigate density-fluctuated states of nuclear matter as a result of clustering below the saturation density ${\rho }_0$ by description in terms of the Bloch function. The Bloch description has the advantage of a unified representation for a density-fluctuated state from an aggregate of uncorrelated clusters in extremely low-density regions to the plane-wave state of uniform matter in relatively high-density regions. We treat the density-fluctuated states due to $\alpha$ and ${}^{16}\mathrm{O}$ clustering in symmetric nuclear matter and due to ${}^{10}\mathrm{He}$ clustering in asymmetric nuclear matter. The density-fluctuated states develop as the density of matter decreases below each critical density around $0.2–0.4{\rho }_0$ which depends on what kind of effective force we use.

Higher-order anisotropic flows $v_4$ and $v_6$ of charged hadrons in heavy-ion collisions at the Relativistic Heavy Ion Collider are studied in a multiphase transport model that has previously been used successfully for describing the elliptic flow $v_2$ of identified hadrons in these collisions. We find that the same parton scattering cross section of about $10\text{mb}$ used in explaining the measured $v_2$ of charged hadrons can also reproduce the recent data on their $v_4$ and $v_6$ from $\text{Au}+\text{Au}$ collisions at $\sqrt{s}=200A\text{GeV}$. It is further found that $v_4$ is a more sensitive probe of the initial partonic dynamics in these collisions than $v_2$. Moreover, higher-order parton anisotropic flows are non-negligible and satisfy the scaling relation $v_{n,q}\left(p_T\right)\sim v_{2,q}^{n∕2}\left(p_T\right)$, which leads naturally to the observed similar scaling relation among hadron anisotropic flows when the coalescence model is used to describe hadron production from the partonic matter.

Considering two-body integral equations we show how they can be dimensionally reduced by integrating exactly over the azimuthal angle of the intermediate momentum. Numerical solution of the resulting equation is feasible without employing a partial-wave expansion. We illustrate this procedure for the Bethe-Salpeter equation for pion-nucleon scattering and give explicit details for the one-nucleon-exchange term in the potential. Finally, we show how this method can be applied to pion photoproduction from the nucleon with $\pi N$ rescattering being treated so as to maintain unitarity to first order in the electromagnetic coupling. The procedure for removing the azimuthal-angle dependence becomes increasingly complex as the spin of the particles involved increases.

Radiative nucleon-deuteron capture and two- and three-body photodisintegration of the three-nucleon bound state are described. The description uses the purely nucleonic charge-dependent CD-Bonn potential and its coupled-channel extension CD Bonn $+\Delta$. The $\Delta$-isobar excitation yields an effective three-nucleon force and effective two- and three-nucleon currents beside other $\Delta$-isobar effects; they are mutually consistent. Exact solutions of three-particle equations are employed for the initial and final states of the reactions. The current has one-baryon and two-baryon contributions and couples nucleonic with $\Delta$-isobar channels. $\Delta$-isobar effects on the observables are isolated. Shortcomings of the theoretical description are discussed and their consequence for the calculation of observables is estimated.

High-spin states in ${}_{35}{}^{72}\mathrm{Br}_{37}$ were studied using the ${}^{40}\mathrm{Ca}\left({}^{36}\mathrm{Ar},3pn\right)$ reaction. The existing level scheme has been significantly modified and extended. Evidence has been found for a spin reassignment of $-1\hslash$ to the previously observed negative-parity band, which carries implications for the interpretation of a signature inversion in this structure. One signature of the previously assigned positive-parity band is interpreted as negative parity and has been extended to $I^{\pi }=\left({22}^{-}\right)$ and its signature partner has been observed up to $I^{\pi }=\left({19}^{-}\right)$ for the first time. The remaining positive-parity band has been extended to $I^{\pi }=\left({29}^{+}\right)$. A sequence of states observed to $I^{\pi }=\left({22}^{+}\right)$ may be the signature partner of this structure. Configurations have been assigned to each of these three structures through comparisons to cranked Nilsson-Strutinsky calculations.

$B\left(E2\right)$ values from isomeric states near closed shells are discussed in the context of the behavior of seniority conserving transitions induced by even tensor operators. This result provides a signature for the transition from the seniority regime to collective motion that can be of use in identifying shell structure in exotic nuclei.

A model is developed for the reaction $\gamma +d\to K^{+}+\Lambda +n$ that includes both impulse and rescattering contributions. Most of the well-established resonances of spins $\frac{1}{2}$ and $\frac{3}{2}$ below $1.9\text{GeV}$ are incorporated in the model. Initial estimates for the relevant coupling strengths are extracted from empirical information and SU(3) symmetry relations. For certain resonances, these initial estimates are modified to bring the cross sections calculated for certain elementary processes related to the rescattering terms in rough qualitative agreement with the empirical cross sections for these processes. For the $N^{*}$ and $\Delta$ resonances included in the model, off-shell width extrapolations are obtained by treating the energy and momentum dependence of each decay channel separately. Since the main intent of the study is to ascertain the importance of the rescattering terms in the reaction amplitudes, no attempt has been made to include final state correlations. To represent the initial state, a nonrelativistic deuteron wave function is employed. Results are presented for the differential cross section in the deuteron rest frame at fixed kaon energy and angle. The results indicate that rescattering contributions to the photoproduction of kaons from the deuteron may be significant over a wide kinematical range.

A unified formula which describes the (pseudo)rapidity distributions of charged particles produced in high energy collisions is presented. The calculated results are compared and found to be in agreement with the experimental data of $e^{+}{e}^{-}$, $p\overline{p}$, and $AA$ collisions at high energies.

We study the sensitivity of neutral-current neutrino-nucleus scattering to the strange-quark content of the axial-vector form factor of the nucleon. A model-independent formalism for this reaction is developed in terms of eight nuclear-structure functions. Taking advantage of the insensitivity of the ratio of proton $(\nu ,p)$ to neutron $(\nu ,n)$ yields to distortion effects, we compute all structure functions in a relativistic plane-wave impulse approximation approach. Further, by employing the notion of a bound-state nucleon propagator, closed-form, analytic expressions for all nuclear-structure functions are developed in terms of an accurately calibrated relativistic mean-field model. Using a strange-quark contribution to the axial-vector form factor of $g_A^s=-0.19$, a significant enhancement in the proton-to-neutron yields is observed relative to one with $g_A^s=0$.

We consider the exclusive reaction $pp\to pp{\pi }^0{e}^{+}{e}^{-}$ at energies near the $\eta$ production threshold. Different channels contribute to this reaction. One of them—the production of $\eta$ mesons and its subsequent rare decay $\eta \to {\pi }^0{e}^{+}{e}^{-}$—is considered as a signal to which the other channels constitute the background. The conditions under which the signal can be larger than background are investigated.

A unitary transformation of the three-body Hamiltonian which describes a system of two charged and one neutral particles is constructed such that the Coulomb potential which acts between the charged particles is explicitly eliminated. The transformed Hamiltonian and, in particular, the transformed short-range pair interactions are worked out in detail. Thereby it is found that, after transformation, the short-range potentials acting between the neutral and either one of the charged particles become simply Fourier transformed but, in addition, multiplied by a function that represents the Coulombic three-body correlations originating from the action of the other charged particle on the considered pair. This function which is universal as it does not depend on any property of the short-range interaction is evaluated explicitly and its singularity structure is described in detail. In contrast, the short-range potential between the charged particles remains of two-body type but occurs now in the “Coulomb representation.” Specific applications to Yukawa and Gaussian potentials are given. Since the Coulomb-Fourier-transformed Hamiltonian does no longer contain the Coulomb potential or any other effective interaction of long range, standard methods of short-range few-body scattering theory are applicable.

Recoil nucleon transferred polarization observables in coincidence quasielastic electron scattering are studied within the relativistic distorted wave impulse approximation. Results for response functions and polarization asymmetries are discussed for proton knockout from $p_{1∕2}$, $p_{3∕2}$, and $s_{1∕2}$ shells in ${}^{16}\mathrm{O}$. The impact of spinor distortion is examined by comparing the fully relativistic calculation with results obtained by projecting out the negative-energy components. In particular, a careful analysis of effects linked to the description of the bound and scattered relativistic nucleon wave functions is presented. The high sensitivity of some polarization observables to the dynamical enhancement of the lower components, already shown within the relativistic plane wave impulse approximation, is proven to be maintained in the relativistic distorted wave approach. Semi-relativistic approaches based on the effective momentum approximation are also studied. Finally, comparison with experimental data and a brief analysis of effects linked to medium modified form factors is presented.

The fission of lead projectiles has been investigated at the CERN SPS by the NA50 experiment. For this study, a Cherenkov quartz detector was added to the standard NA50 setup to measure the charge of projectilelike fragments. The data collected on different targets at 40 and $158\text{GeV}∕c$ per nucleon are presented here. The contributions arising from the nuclear and the electromagnetic fission mechanism are extracted from the measured fission cross sections; the electromagnetic contribution is then compared to the Weizsäcker-Williams predictions.

We present a complete Monte Carlo simulation of the response of a realistic model of a deep-underwater Cherenkov detector to supernova neutrinos. The various sources of noise are discussed in detail and a statistical treatment of the data is proposed based upon integration on a properly chosen time interval. The results show that the neutrino flux emitted by a supernova exploding in our galaxy can be detected from such a telescope. The possibility of retrieving information on the supernova direction from the asymmetry in the emitted Cherenkov light has been considered, showing that this approach does not allow an accurate localization of the $\nu$ source.