arXiv:hep-ph/0610415·v3·High Energy Physics — Phenomenology

Large mass expansion in two-loop QCD corrections of para-charmonium decay

Abstract

We calculate the two-loop QCD corrections to paracharmonium decays $e t a_{c} r i g h t a r r o w g amma g amma$ and $e t a_{c} r i g h t a r r o w g g$ involving light-by-light scattering diagrams with light quark loops. Artificial large mass expansion and convergence improvement techniques are used to evaluate these corrections. The obtained corrections to the decays $e t a_{c} r i g h t a r r o w g amma g amma$ and $e t a_{c} r i g h t a r r o w g g$ account for $- 1.25$ and $- 0.73$ of the leading order contribution, respectively.

Comments: 24 pages, 10 figures; REVTeX version; Version to appear in Phys. Rev. D, 9 pages, 4 figures