Hard Break-Up of Two-Nucleons from the 3He Nucleus
  We investigate a large angle photodisintegration of two nucleons from the $^3$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 NN scattering, the HRM allows to express the amplitude of a two-nucleon break-up reaction through the convolution of photon-quark scattering, $NN$ hard scattering amplitude and nuclear spectral function. The photon-quark scattering amplitude can be explicitly calculated in the high energy regime, whereas for $NN$ 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 $s^{-11}$. Secondly, the $s^{11}$ weighted cross section will have the shape of energy dependence similar to that of $s^{10}$ weighted $NN$ elastic scattering cross section. Also one predicts an enhancement of the $pp$ breakup relative to the $pn$ breakup cross section as compared to the results from low energy kinematics. Another result is the prediction of different spectator momentum dependencies of $pp$ and $pn$ breakup cross sections. This is due to the fact that same-helicity $pp$-component is strongly suppressed in the ground state wave function of $^3$He. Because of this suppression the HRM predicts significantly different asymmetries for the cross section of polarization transfer $NN$ breakup reactions for circularly polarized photons. For the $pp$ breakup this asymmetry is predicted to be zero while for the $pn$ it is close to ${2\over 3}$. 
Misak M Sargsian and Carlos Granados