Axial anomaly and the precise value of the pi0 ---> 2 gamma decay width

The anomaly in the vacuum expectation value of the product of axial and two vector currents (AVV) in QCD is investigated. The goal is to determine from its value the

\pi^0 \to 2 \gamma

decay width with high precision. The sum rule for AVV formfactor is studied. The difference

f_{\pi^0} - f_{\pi^+}

caused by strong interaction is calculated and appears to be small. The

\pi^0 - \eta

mixing is accounted. The

\pi^0 \to 2 \gamma

decay width determined theoretically from the axial anomaly is found to be

\Gamma(\pi^0 \to 2 \gamma) = 7.93 eV

with an error

\sim 1.5%

. The measurement of the

\pi^0 \to 2 \gamma

decay width at the same level of accuracy would allow one to achieve a high precision test of QCD.

11.15.-q
12.38.Aw
11.30.Qc
current: axial
current: vector
anomaly: axial
quantum chromodynamics
form factor: sum rule
pi0: radiative decay
photon: pair production

References(19)

Figures(0)

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