O(4) Symmetry and the Regge Trajectory of the Pion
Abstract
An off-shell generalization of O(4) symmetry is developed, which is applicable to unequal-mass 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 high-energy 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 N¯Nπ vertex function then shows a zero near t=0, in agreement with some fits to high-energy data, but this zero is factorizable. Moreover, a model is exhibited that seems consistent with the hypothesis of partially conserved axial-vector current.
- Publication:
-
Physical Review
- Pub Date:
- October 1968
- DOI:
- 10.1103/PhysRev.174.1932
- Bibcode:
- 1968PhRv..174.1932F