Final State Interaction in Neutron Deuteron Charge Exchange Reaction at Small Transfer Momentum

Analysis of the $nd\to p(nn)$ reaction in a Gev-energy region is performed in the framework based on the multiple-scattering theory for the few nucleon system. The special kinematic condition, when momentum transfer from neutron beam to final proton closes to zero, is considered. The possibility to extract the spin-flip term of the elementary $np\to pn $ amplitude from nd-breakup process is investigated. The energy dependence of the ratio $R=\frac{d\sigma_{nd}} {d\Omega} / \frac{d\sigma_{np}}{d\Omega}$ is obtained taking account of the final state interaction two outgoing neutrons in $^1 S_0$-state