Investigating convergence of the reaction γp → π±Δ and tensor meson a2 exchange at high energy

A Regge approach to the reaction processes γp→π−Δ++ and γp→π+Δ0 is presented for the description of existing data up to Eγ=16GeV. The model consists of the t-channel π(139)+ρ(775)+a2(1320) exchanges which are reggeized from the relevant Born amplitude. Discussion is given on the minimal gauge prescription for the π exchange to render convergent the divergence of the u-channel Δ-pole in the former process. A new Lagrangian is constructed for the a2NΔ coupling in this work and applied to the process for the first time with the coupling constant deduced from the duality plus vector dominance. It is shown that, while the π exchange dominates over the process, the role of the a2 exchange is crucial rather than the ρ in reproducing the cross sections for total, differential, and photon polarization asymmetry to agree with data at high energy.