Tensor analyzing powers in forward angle exclusive π - meson photoproduction on deuteron

Tensor analyzing powers in forward angle exclusive π-meson photoproduction on deuteron. Abstract The target tensor analyzing powers of the process γd → π − pp had been studied in the plane wave impulse approximation, if both ejected protons are detected in coincidence and in the directions, symmetrical respect to the incoming photon momentum , being in the proton plane. The matrix elements of the studied reaction become essentially simple, if the magnitudes of the proton momenta p 1 = p 2 = p are equal. That proton kinematics keeps the ejected pion angle near zero, therefore the one body pion production operator does not include the spin-non-flip term. Moreover, the transition to the triplet, spatially antisymmetric final pp− state is strongly suppressed from the symmetrical deuteron S− state as well as matrix elements have a large dependence from the orientation of the deuteron spin. The values of the T 22 (p) component, calculated with three realistic deuteron wave functions in the proton momentum region p ≥ 350M eV /c and proton polar angle θ ≥ 40 • , differ one from another noticeably. Meson photoproduction from nuclei on a level with elastic and inelastic electron scattering for a long time is an important reaction used for the investigation of the nuclear structure and dynamics. To examine the pion pho-toproduction on the neutrons,that is great particular interest, as a rule, the investigation of the reaction γd → πNN is being used. However the extraction of the information even on the simplest nucleus structure as well as on pion production on a neutron is very complicated by uncertainties aroused from initial and final state interaction, Fermi motion, off-mass-shell effects. Moreover for the charge pion production exclusion principle effect on the final nn or pp system should be taken into consideration. The experimental and theoretical studies of the pion photoproduction reactions involving polarized deuteron target have received considerable attention at present. It is apparent that the polarization observables may provide a means of obtaining additional nuclear dynamics information. We have studied experimentally the differential cross section and tensor target asymmetries of the process γd → π − pp (1) by recording two protons in coincidence in the reaction ed → ppπ − e ′ (2) at the photon point, using the internal polarized deuterium target of the VEPP-3 storage ring [1]. The experimental data have been obtained at large ejected proton momenta 300MeV …