Electro-pion Production from Proton, Deuteron, and Helium-3

Résumé du livre

The cross section for the $p(e, espprimepisp+)n, d(e, espprimepisp+)2n$ and $sp3He(e, espprimepisp+)sp3H$ reactions are calculated using a simple model with pion, nucleon and $Delta$-resonance degrees of freedom for the kinematical conditions used in a recent Saclay experiment. For the $d(e, espprimepisp+)2n$ reaction, final state interactions between the two outgoing neutrons are found to have a large effect. The calculated quenching of the $pisp+$ production cross section for the deuterium target is in agreement with that observed experimentally. It is predicted that due to the strong final state interactions in the singlet S state of the two neutrons, the $d(e, espprimepisp+)2n$ cross section can have a large dependence on the orientation of the deuteron spin. For the $sp3He(e, espprimepisp+)sp3H$ reaction, the quenching is predicted to be $sim$0.4 which is in agreement with the unpublished results of the Mainz experiment. The four important contributions to the quenching are identified as: (i) the finite size i.e., the form factor of the trinucleons, (ii) the spin-isospin correlations in the trinucleons, (iii) the finite range of the propagation of the struck proton, and (iv) the possible pion-nucleon final state interactions.