ρ γ*→π (ρ ) transition form factors in the perturbative QCD factorization approach

In this paper, we studied the ρ γ^*→π and ρ γ^*→ρ transition processes and made the calculations for the ρ π transition form factor Q⁴F_{ρ π}(Q²) and the ρ -meson electromagnetic form factors, F_{LL ,LT ,TT}(Q²) and F_{1 ,2 ,3}(Q²), by employing the perturbative QCD (PQCD) factorization approach. For the ρ γ^*→π transition, we found that the contribution to form factor Q⁴F_{ρ π}(Q²) from the term proportional to the distribution amplitude combination ϕ_ρ^T(x₁)ϕ_π^P(x₂) is absolutely dominant, and the PQCD predictions for both the size and the Q²-dependence of this form factor Q⁴F_{ρ π}(Q²) agree well with those from the extended anti-de Sitter/QCD models or the light-cone QCD sum rule. For the ρ γ^*→ρ transition and in the region of Q²≥3 GeV² , furthermore, we found that the PQCD predictions for the magnitude and their Q²-dependence of the F₁(Q²) and F₂(Q²) form factors agree well with those from the QCD sum rule, while the PQCD prediction for F₃(Q²) is much larger than the one from the QCD sum rule.