Electromagnetic properties of ground-state and excited-state pseudoscalar mesons
- Physics Division, Argonne National Laboratory, Argonne, Illinois 60439-4843 (United States)
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)
The axial-vector Ward-Takahashi identity places constraints on particular properties of every pseudoscalar meson. For example, in the chiral limit all pseudoscalar mesons, except the Goldstone mode, decouple from the axial-vector current. Nevertheless, all neutral pseudoscalar mesons couple to two photons. The strength of the {pi}{sub n}{sup 0}{gamma}{gamma} coupling, where n=0 denotes the Goldstone mode, is affected by the Abelian anomaly's continuum contribution. The effect is material for n{ne}0. The {gamma}*{pi}{sub n}{gamma}* transition form factor, T{sub {pi}{sub n}}(Q{sup 2}), is nonzero for all n, and T{sub {pi}{sub n}}(Q{sup 2}){approx_equal}(4{pi}{sup 2}/3)(f{sub {pi}{sub n}}/Q{sup 2}) at large Q{sup 2}. For all pseudoscalars but the Goldstone mode, this leading contribution vanishes in the chiral limit. In this instance the ultraviolet power-law behavior is 1/Q{sup 4} for n{ne}0, and we find numerically T{sub {pi}{sub 1}}(Q{sup 2}){approx_equal}(4{pi}{sup 2}/3)(-<qq>/Q{sup 4}). This subleading power-law behavior is always present. In general its coefficient is not simply related to f{sub {pi}{sub n}}n. The properties of n{ne}0 pseudoscalar mesons are sensitive to the pointwise behavior of the long-range piece of the interaction between light quarks.
- OSTI ID:
- 20698778
- Journal Information:
- Physical Review. C, Nuclear Physics, Vol. 71, Issue 6; Other Information: DOI: 10.1103/PhysRevC.71.065204; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
- Country of Publication:
- United States
- Language:
- English
Similar Records
Flavor symmetry breaking and meson masses.
Nucleon form factors from quenched lattice QCD with domain wall fermions