Electromagnetic properties of ground-state and excited-state pseudoscalar mesons

Journal Article · Wed Jun 01 04:00:00 EDT 2005 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PhysRevC.71.065204· OSTI ID:20698778

Hoell, A; Krassnigg, A; Wright, S V ^[1]; Maris, P ^[2]; Roberts, C D ^[1]

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1. Physics Division, Argonne National Laboratory, Argonne, Illinois 60439-4843 (United States)
2. 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, Journal Name: Physical Review. C, Nuclear Physics Journal Issue: 6 Vol. 71; ISSN 0556-2813; ISSN PRVCAN
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
AXIAL-VECTOR CURRENTS
CHIRAL SYMMETRY
CHIRALITY
COUPLING
CURRENT ALGEBRA
D QUARKS
EXCITED STATES
FORM FACTORS
GROUND STATES
PHOTONS
PIONS
U QUARKS
ULTRAVIOLET RADIATION
WARD IDENTITY