Theoretical Study Of The Nucleon Momentum Distribution In Nu- Cleus

The study of the short-range-correlation (SRC) between nucleon-nucleon pairs is one of the nuclear physics frontiers in recent years. The short-range-correlation pushes nucleons from low momenta (k< κF, where κF is the Fermi momentum of the system) to high momenta (k> κF), creating a high-momentum tail in nucleon momentum dis-tribution. In recent years, there are new progresses in the study of the nucleon momen-tum distribution and the SRC between nucleon-nucleon pairs. For instance, in Science 320,1476 (2008), the high-energy electron-scattering experiment conducted by the J-efferson Lab using the nucleus 12C suggests that about 20% of nucleons are correlated in 12C and 90% of the correlated pairs are in the form of np SRC pairs. Further work in Science 346,614 (2014) using high-energy electron-scattering on 12C,27 Al,56Fe, and 208Pb targets shows that even in heavy, neutron-rich nuclei, the short-range-interactions between nucleons can form correlated high momentum pairs and create a high momen-tum tail in nucleon momentum distribution. For SRC nucleons, the np-pair dominance mainly induced by tensor force causes a greater fraction of protons than neutrons to have high momentum in neutron-rich nuclei. Both the short-range-correlation and the high-momentum component in nucleon momentum distribution are important for many issues in nuclear physics, astrophysics, and particle physics, such as the studies of the nuclear symmetry energy, the neutron star, and the electro-weak interaction. The high-energy electron-scattering experiments have been used to study the nucleon momentum distribution in finite nucleus. In this paper, the intermediate energy heavy-ion collision is proposed as a new possible way to study it.In Chapter two, the Boltzmann-Uehling-Uhlenbeck (BUU) transport model and the neutron-proton bremsstrahlung in intermediate energy heavy-ion collision are introduced. The BUU model is based on the Boltzmann-Uehling-Uhlenbeck (BUU) equation, which describes the time evolution of the phase space distribution function f (r, p, t) in semi-classical approximation. In the BUU theory model, the hadron-hadron cross sections and the information of nuclei in heavy-ion collision, such as the nucleon momentum distribution and the mean field potential, are input into the program in the initialization step. The comparative analysis of the observables in these simulations and experimental measurements helps extract the information of the EOS and nuclear symmetry energy. Since once produced photons escape almost freely from the nucle-ar environment of nuclear reactions, we choose the neutron-proton bremsstrahlung photons to probe the nucleon momentum distribution of finite nuclei in intermediate energy heavy-ion collisions.In Chapter three we carry out the BUU simulations using two different nucleon momentum distributions, namely the ideal free Fermi gas (FFG) momentum distri-bution and the one with SRC induced high-momentum tail (HMT). Specifically, we study the nucleon momentum distribution in 12C and 124Sn using the 12C+12C head on collisions at beam energies of 50 MeV/nucleon and 140 MeV/nucleon, and the 124Sn+124Sn head on collisions at beam energies of 50 MeV/nucleon. The high en-ergy bremsstrahlung photons from intermediate energy collisions are used to study the effects of the HMT on the reactions. The calculated results show that the HMT in-fluences the final observables significantly. For instance, at Ebeam= 50 MeV/nucleon, there are 40% growth of the high energy (50 MeV< Eγ< 125 MeV) photon pro-duction,68% growth of the high kinetic energy (40 MeV< Ec.m.< 100 MeV) free proton emission probability, and 76% growth of such high kinetic energy free neutron emission probability in the HMT case compared with that in the FFG case. Cancel-ing out uncertainties from np scattering cross section as well as from photon produc-tion probability, the ratio of photon production at different incident beam energies (50 MeV/nucleon and 140 MeV/nucleon) is suggested as a potential observable to probe the high-momentum component in nucleon momentum distribution of finite nucleus.Finally, a summary and some outlooks are given in Chapter four.