THE HIGH MOMENTUM AND ENERGY BEHAVIOR OF THE NUCLEON SPECTRAL-FUNCTION OF NUCLEAR-MATTER WITHIN THE BRUECKNER-BETHE-GOLDSTONE APPROACH

The nuclear single-particle spectral function is considered in the reg ion of high momentum and high removal energy. For these kinematical co nditions, far away from the quasi-particle peak, the spectral function is expected to be dominated by nucleon-nucleon correlations. It has b een previously argued that the spectral function can be written as a c onvolution between the two-body relative momentum distribution and the corresponding centre-of-mass distribution of the correlated pairs whi ch characterize the structure of the ground state in this energy-momen tum region. It is shown that the convolution model can be microscopica lly derived from the Brueckner-Bethe-Goldstone (BBG) expansion. At the same time, this result also allows us to establish a direct link betw een the spectral function and the defect function of the BBG theory. F rom a numerical comparison with the microscopic spectral function the convolution model turns out to be highly accurate in the relevant mome ntum and energy range.