Nucleon momentum distributions in $^3$He and three-body interactions

Abstract

We calculate momentum distributions of neutrons and protons in $^3$He in the framework of a model which includes 3N interactions together with 2N interactions. It is shown that contribution of 3N interactions becomes essential in comparison with contribution coming from 2N interaction for internal momentum in $^3$He $k>$~250~MeV/c. We also compare calculated momentum distribution of protons with so-called empirical momentum distribution of protons extracted from A$(^3\mathrm{He},p)$ breakup cross-sections measured for protons emitted at zero degree. It is concluded that 3N interactions cannot completely explain the disagreement between the available data on the empirical momentum distribution of protons in $^3\mathrm{He}$ and calculations based on 2N interaction, which is observed at high momentum region of the momentum distribution, $k>$~250~MeV/c.