B-→π-π0/ρ-ρ0 to next-to-next-to-leading order in QCD factorization

The approximate tree decays B-→π-π0/ρ-ρ0 may serve as benchmark channels for testing the various theoretical descriptions of the strong interaction dynamics in hadronic B meson decays. The ratios of hadronic and differential semileptonic B→πlν/ρlν decay rates at maximum recoil provide particularly clean probes of the QCD dynamics. We confront the recent next-to-next-to-leading order calculation in the QCD factorization framework with experimental data and find support for the factorization assumption. A detailed analysis of all tree-dominated B→ππ/πρ/ρρ decay modes seems to favor somewhat enhanced color-suppressed amplitudes, which may be accommodated in QCD factorization by a small value of the first inverse moment of the B meson light-cone distribution amplitude, λB≅250 MeV. Precise measurements of the semileptonic B→ρlν spectrum could help to clarify this point.