TTP09-22 B- -> pi- pi0 / rho- rho0 to NNLO in QCD factorization

pi- pi0 / rho- rho0 to NNLO in QCD factorization > The approximate tree decays B- → pi- pi0/rho- rho0 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 → pi l nu/rho l nu decay rates at maximum recoil provide particularly clean probes of the QCD dynamics. We confront the recent NNLO calculation in the QCD factorization framework with experimental data and find support for the factorization assumption. A detailed analysis of all tree-dominated B → pi pi/pi rho/rho rho decay modes seems to favour somewhat enhanced colour-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, lambda_B ~ 250 MeV. Precise measurements of the B → rho l nu spectrum could help to clarify this point.