Rho-pion transition form factors in the kT -factorization formalism revisited

Jun Hua, Shan Cheng, Ya-lan Zhang, Zhen-Jun Xiao
2018 Physical Review D  
We revisit the evaluations for the spacelike and timelike ρπ transition form factors F_ρπ(Q^2) and G_ρπ(Q^2) with the inclusion of the the next-to-leading order (NLO) QCD contributions in the framework of the k_T factorization theorem. The infrared divergence is regularized by the transversal momentum carried by external valence quarks, and ultimately absorbed into the meson wave functions. In the region of Q^2 ≤ 2 GeV^2 , where PQCD factorization apporach applicable, the NLO contribution can
more » ... ing no larger than 35% enhancement to the spacelike form factor F_ρπ(Q^2). For the timelike form factor derived under the kinematic exchanging symmetry, this contribution is also under control when the momentum transfer squared is large enough. We also prolong our prediction into the small Q^2 region by taking the Lattice QCD results into account, and subsequently obtain the coupling g_ρπγ = G_ρπ(0)=0.596.
doi:10.1103/physrevd.97.113002 fatcat:obtn6zqvpbedjmgbzipimiqihy