2013/02/11 by T.N. Pham, Pham, T. N.
Physics and Astronomy · #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #High-Energy Particle Collisions Research
paper · pdf · doi:10.48550/arxiv.1302.2431
The success of the Adler-Bell-Jackiw(ABJ) chiral anomaly prediction for π0→ γγ decay rate shows that non-anomaly terms would make a negligible contribution to the decay rate, in agreement with the Sutherland-Veltman theorem. Thus the conventional qq bound-state description of the pion could not be valid since it would produce a π0→ γγ decay amplitude not suppressed in the soft pion limit, in contradiction with the Sutherland-Veltman theorem. Therefore, if the pion is to be treated as a qq bound state, this bound state would be a longitudinal axial-vector meson. In this paper, we consider the pion to be a longitudinal axial-vector meson qq bound state with derivative coupling for the pion qq Bethe-Salpeter(BS) wave function. We shall show that this BS wave function could produce a suppressed π0→ γγ decay amplitude in the soft pion limit, in agreement with the Sutherland-Veltman theorem. This explains the almost perfect agreement of the anomaly prediction with experiment and the suppression of the virtual one-photon exchange contribution in η→ 3π decay. The Goldstone boson equivalence theorem used for longitudinal gauge bosons scattering in the electroweak standard model then identifies the longitudinal axial-vector meson qq bound state with the pion.