Hard breakup of two nucleons from theHe3nucleus

Abstract

We investigate a large angle photodisintegration of two nucleons from the $^{3}\mathrm{He}$ nucleus within the framework of the hard rescattering model (HRM). In the HRM a quark of one nucleon knocked out by an incoming photon rescatters with a quark of the other nucleon leading to the production of two nucleons with large relative momentum. Assuming the dominance of the quark-interchange mechanism in a hard nucleon-nucleon scattering, the HRM allows the expression of the amplitude of a two-nucleon breakup reaction through the convolution of photon-quark scattering, $\mathit{NN}$ hard scattering amplitude, and nuclear spectral function, which can be calculated using a nonrelativistic $^{3}\mathrm{He}$ wave function. The photon-quark scattering amplitude can be explicitly calculated in the high energy regime, whereas for $\mathit{NN}$ scattering one uses the fit of the available experimental data. The HRM predicts several specific features for the hard breakup reaction. First, the cross section will approximately scale as ${s}^{\ensuremath{-}11}$. Second, the ${s}^{11}$ weighted cross section will have the shape of energy dependence similar to that of ${s}^{10}$ weighted $\mathit{NN}$ elastic scattering cross section. Also one predicts an enhancement of the $\mathit{pp}$ breakup relative to the $\mathit{pn}$ breakup cross section as compared to the results from low energy kinematics. Another result is the prediction of different spectator momentum dependencies of $\mathit{pp}$ and $\mathit{pn}$ breakup cross sections. This is due to the fact that the same-helicity $\mathit{pp}$-component is strongly suppressed in the ground state wave function of $^{3}\mathrm{He}$. Because of this suppression the HRM predicts significantly different asymmetries for the cross section of polarization transfer $\mathit{NN}$ breakup reactions for circularly polarized photons. For the $\mathit{pp}$ breakup this asymmetry is predicted to be zero while for the $\mathit{pn}$ it is close to $\frac{2}{3}$.