| Popis: |
The study of inelastic channels induced by the nucleon-nucleon (NN) system has a two-fold interest: first, this elementary process has to be understood in itself, for example through the isobar model mechanism, second, its knowledge is necessary to interpret more complicated reactions induced by a nucleon probe with nuclei; for example, any microscopic calculation of the (n,p) charge exchange reaction in the Δ region requires the knowledge of np and nn→NNπ+ in this region of the phase space. Thus, the study of the one-pion production channel in NN interaction must be undertaken as carefully as the study of the elastic channel to be able to treat all channels on the same footing in a global description of these elementary hadronic processes. In the energy region ranging up to the GeV, a large body of data already exists. Extensive studies of proton-proton and neutron-proton elastic scattering involving complete determination of amplitudes from the measurement of spin observables by using polarized beams and targets, have been made. Many data have been obtained also for the pp→dπ+ and the pp→pnπ+ inelastic reactions, both proceeding through a mechanism dominated by the existence of an intermediate NΔ state, as can be seen from the success of the various approaches using such an isobar model1. |
