https://doi.org/10.1140/epja/i2013-13084-9
Regular Article - Theoretical Physics
Lattice QCD and the two-photon decay of the neutral pion
PRISMA Cluster of Excellence, Institut für Kernphysik and Helmholtz Institute Mainz, Johannes Gutenberg-Universität Mainz, D-55099, Mainz, Germany
* e-mail: meyerh@kph.uni-mainz.de
Received:
8
March
2013
Revised:
22
May
2013
Accepted:
24
May
2013
Published online:
17
July
2013
Two-photon decays probe the structure of mesons and represent an important contribution to hadronic light-by-light scattering. For the neutral pion, the decay amplitude tests the effects of the chiral anomaly; for a heavy quarkonium state, it measures the magnitude of its wave function at the origin. We rederive the expression of the decay amplitude in terms of a Euclidean correlation function starting from the theory defined on the torus. The derivation shows that for timelike photons the approach to the infinite-volume decay amplitude is exponential in the periodic box size.
© SIF, Springer-Verlag Berlin Heidelberg, 2013
