1S0 diproton formation in the pd→ppn and pp→ppπ0 reactions and short-range nn interaction

Full text: Hadronic processes pd→dp and pp→dπ+ at high transferred momenta to the final deuteron are studied with the aim to get information on nucleon-nucleon interaction at short distances in the region of nuclear core (rNN<0.5 fm). A crucial test for existing phenomenological models of these processes can be obtained in studying reactions the formation of the diproton (pp)s, i.e. two protons being in the 1S0 state of their relative motion with low excitation energy E<3 MeV, instead of the deuteron in the final state. Difference in the quantum numbers (spin J, isospin T, and orbital angular momentum L) of the diproton (J=L=0,T=1) and deuteron (J=1, T=0, L=0.2) at the same kinematics of the considered processes could lead to remarkable qualitative features in observables and, therefore, get new insight into the underlying dynamics. In particularly, mechanisms with excitation of the Δ-isobar are suppressed for the diproton channel what increases a sensitivity of observables to the shot-range part of the NN interaction. Theoretical analysis of the data on the pd→(pp)sn reaction obtained recently at COSY in kinematics of pd-backward elastic scattering at 0.6 -1.9 GeV allowed one to conclude that among available phase-shift equivalent NN interaction potentials only rather soft interaction at short distances, like the CD Bonn model, provide agreement with this data. On the contrary, more hard interactions, like RSC and Paris, create too intensive high momentum components of the NN wave function and, thus, lead to strong disagreement with the pd→(pp)sn data. New theoretical analysis of this reaction , performed within the mechanisms involving the sub-processes pN→(pp)sπ and πd→pN, confirms to large extent the above conclusion. The first data on the reaction pp→(pp)sπ0 obtained at 0.8 GeV are considered earlier together with the pd→(pp)sn and found to be compatible with dominance of the N*-baryon exchange mechanism of the single pion production at this energy