Witnessing the hadronic collision events at close quarters

It is seen that in the three body final state of a nucleon knockout reaction the residual nucleus not only bears testimony to the dynamics of the knocked out nucleon before the event but also can testify the happening at the time of the hard collision event. This arises mainly because of the distorting optical potentials of the residual nucleus with the knockout partners. In ⁴⁰Ca(p, 2p) knockout reaction the optical distortion effects are large enough to be able to differentiate between strong peripheral bruising or the deep interpenetration of the two protons at the time of knockout. Similar effect is witnessed in the proton knockout using pions. Many stronger evidences of the effect of varying behaviour of the knockout vertex exist in the nucleon cluster knockout reactions which were only viewed as unexplained large anomalies. Evidences are provided where the different short distance behaviour of the knockout vertex t-matrix effective interaction produced huge differences in the finite range (FR) distorted wave impulse approximation (DWIA) predictions of various knockout reactions. These observations enhance the possibility of observing the multiquark objects (dibaryons, pentaquark eta.) through nucleon knockout reactions if they are produced at the knockout vertex by the incident hadron beam. (author)