Probing QFS mechanism with the 12C(p, 2p)11B reaction in inverse kinematics

The reaction mechanism of the quasi-free scattering (QFS) reaction 12C( p , 2 p )11B is investigated in inverse and complete kinematics using a 12C beam at 400 MeV/nucleon impinging on a polyethylene (CH2) target. A complete set of kinematic observables characterizing the three-body final state is obtained through the exclusive reconstruction of the 11B recoil fragment and the two outgoing protons. For the first time, a systematic Treiman-Yang test is applied to inverse-kinematics ( p , 2 p ) reactions with a heavy-ion beam, taking advantage of the large phase space covered by the experimental setup, particularly in non-coplanar kinematic configuration. This model-independent test confirms the predominance of the QFS reaction mechanism. The characteristic dependence of the Treiman-Yang angle on the azimuthal correlation of the outgoing protons, along with other kinematic signatures, provides further evidence for the single-step proton knockout process.