O(4)Symmetry and the Forward Photoproduction of Pions at High Energies

Forward photoproduction of pions is studied at high energies with the use of $O\left(4\right)\mathrm{}$ symmetry. It is shown that, in this limit, the asymptotic contribution to the amplitude comes from a unique conspiring family of Regge poles of a definite $O\left(4\right)\mathrm{}$ class. The use of $O\left(4\right)\mathrm{}$ symmetry in the presence of unequal masses ($\gamma N\to \pi N$) is commented on.