Coherent electroproduction of pions from 3He

The 3He(e,e'π+)3H reaction is the simplest of the coherent charged pion electroproduction reactions in nuclear physics. It is sensitive to the structure of the trinucleons, and can be studied with the high duty factor electron accelerators now available. It may also provide some insight for understanding the basic p(e,e'π+)n reaction if the latter can be described within the constituent quark models of nucleons. In this work, we calculate the ratio of p(e,e'π+)n and 3He(e,e'π+)3H cross sections for two kinematical conditions with invariant photon-nucleon mass W=1160 and 1230 MeV, respectively. The four important contributions to this ratio 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. Together they reduce the ratio of the cross section to ∼0.4 in this kinematic range. copyright 1996 The American Physical Society