Application of hard-pion three-point functions
Some comparisons with experiment of the hard-pion three- point functions obtained from SU(2)×SU(2) current algebra are given. Available experimental data involving π,ρ, A1, and σ mesons are examined. The hard-pion current-algebra method i is used to calculate the decays ρ→π+π,A1→π+ρ, and σ→π+π, and the electromagnetic form factor of the pion Peripheral processes such as π+N→ρ+N are also examined as a test of meson-vertex functions for spacelike momentum transfers. Here, to reproduce correctly the momentum-transfer dependence at the nucleon vertex, a new extrapolation for the pionic nucleon form factor is introduced, using the Goldberger-Treiman relation. The results of the above calculations are found to be consistent with the present experimental situation. Current-algebra predictions for the γ+N→A1+N cross section and the decays A1→π+γ and A1→π+σ are given. A cross section of about 0.1 μb is obtained for the A1 photoproduction, which is on the verge of being detectable