Neutral pion photoproduction on the proton near threshold and the chiral symmetry
- 1 March 1989
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review C
- Vol. 39 (3), 1207-1209
- https://doi.org/10.1103/physrevc.39.1207
Abstract
The recent precise measurements of the neutral pion photoproduction on the proton near threshold seems to be inconsistent with the predictions of the low-energy theorems on photoproduction of pions. In this note, we have sought to resolve this problem, in the framework of an approximate SU(2)×SU(2) symmetry of the pion-nucleon dynamics, by incorporating the contribution from the nucleon matrix elements of the equal-time commutator between the divergence of the axial-vector current and the electromagnetic current, which was introduced earlier by Furlan et al. We find that a mean value of the nonstrange quark mass m^=1/2(+)=(7±2) MeV, leads to an estimate of the symmetry breaking terms compatible with experiment.
Keywords
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