Universal behavior of the [Formula: see text] transition form factors

Dmitri Melikhov; Berthold Stech

doi:10.1016/j.physletb.2012.10.052

Universal behavior of the [Formula: see text] transition form factors

Phys Lett B. 2012 Dec 5;718(2):488-491. doi: 10.1016/j.physletb.2012.10.052.

Authors

Dmitri Melikhov^{1

2

3}, Berthold Stech⁴

Affiliations

¹ HEPHY, Austrian Academy of Sciences, Nikolsdorfergasse 18, A-1050 Vienna, Austria.
² Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria.
³ SINP, Moscow State University, 119991 Moscow, Russia.
⁴ ITP, Heidelberg University, Philosophenweg 16, D-69120, Heidelberg, Germany.

Abstract

The photon transition form factors of π, η and [Formula: see text] are discussed in view of recent measurements. It is shown that the exact axial anomaly sum rule allows a precise comparison of all three form factors at high-[Formula: see text] independent of the different structures and distribution amplitudes of the participating pseudoscalar mesons. We conclude: (i) The πγ form factor reported by Belle is in excellent agreement with the nonstrange [Formula: see text] component of the η and [Formula: see text] form factors obtained from the BaBar measurements. (ii) Within errors, the πγ form factor from Belle is compatible with the asymptotic pQCD behavior, similar to the η and [Formula: see text] form factors from BaBar. Still, the best fits to the data sets of πγ, ηγ, and [Formula: see text] form factors favor a universal small logarithmic rise [Formula: see text].