Measurement of coherent π0 photoproduction on3He and3H in the resonance region

Two-Body Mechanisms in Pion Photoproduction on the Trinucleon

“…In the region of Q 2 > 8f m −2 , calculations dramatically fail to explain existing 3 He(γ, π + ) 3 H data, underestimating them by up to two orders of magnitude. Similar discrepancies were found in coherent π 0 photoproduction on 3 He and 3 H [4], in elastic pion scattering at backward angles [2,5], as well as in pion single charge exchange and pion induced eta production on 3 He at higher energies [2,6].…”

“…From our derivation it is clear that these novel two-body mechanisms are not a special feature of the 3 He(γ, π + ) 3 H process but should play an important role in all scattering and production processes at high momentum transfer, as long as the nucleus remains in its ground state. Such processes are coherent π 0 photoproduction on the deuteron or 4 functions [12]. The dash-dotted curve includes the corrections due to the coupling with the break-up channels and the full line shows our complete calculation with the additional novel two-body contribution of Fig.…”

“…production processes at high momentum transfer, as long as the nucleus remains in its ground state. Such processes are coherent π 0 photoproduction on the deuteron or 4…”