Next-to-leading-order time-like pion form factors in [formula omitted] factorization

Abstract

We calculate the time-like pion–photon transition form factor and the pion electromagnetic form factor up to next-to-leading order (NLO) of the strong coupling constant in the leading-twist kT factorization formalism. It is found that the NLO corrections to the magnitude (phase) are lower than 30% (30°) for the former, and lower than 25% (10°) for the latter at large invariant mass squared Q2>30 GeV2 of the virtual photons. The increase of the strong phases with Q2 is obtained, consistent with the tendency indicated by experimental data. This behavior is attributed to the inclusion of parton transverse momenta kT, implying that the kT factorization is an appropriate framework for analyzing complex time-like form factors. Potential extensions of our formalism to two-body and three-body hadronic B meson decays are pointed out.