O(4) Symmetry and the Regge Trajectory of the Pion
Abstract
An offshell generalization of O(4) symmetry is developed, which is applicable to unequalmass reactions involving arbitrary spins. The symmetry breaking at t≠0 is also investigated. These methods are used to analyze the hypothesis that the pion Regge trajectory has the Toller quantum number M=1 at zero momentum transfer, as seems to be implied by highenergy photoproduction data. We find that if this hypothesis is correct, then the pion trajectory is necessarily quite complicated. The M=1 trajectory must mix with another trajectory. The N̄Nπ vertex function then shows a zero near t=0, in agreement with some fits to highenergy data, but this zero is factorizable. Moreover, a model is exhibited that seems consistent with the hypothesis of partially conserved axialvector current.
 Publication:

Physical Review
 Pub Date:
 October 1968
 DOI:
 10.1103/PhysRev.174.1932
 Bibcode:
 1968PhRv..174.1932F