Leading-power contributions toB→π,ρtransition form factors

Abstract

We calculate the B → π, ρ transition form factors in the framework of perturbative QCD to leading power of 1/MB , MB being the B meson mass. We explain the basic principle by discussing the pion electromagnetic form factor. It is shown that the logarithmic and linear singularities occurring at small momentum fractions of light meson distribution amplitudes do not exist in a self-consistent perturbative analysis, which includes k ⊥ and threshold resummations. *

Threshold resummation for exclusiveBmeson decays

“…Another B meson distribution amplitudeφ B (x) = [φ + (x) − φ − (x)]/2 is power-suppressed, since its first nonvanishing moment starts with O(1/M B ) [16]. It has been confirmed, contrary to the conclusion in [24], that the contribution fromφ B is less important than that from φ B [25].…”

“…(35). The difference between the above values and the expected one f + (0) ∼ 0.3 can be resolved by taking into account higher-twsit contributions [16]. Including two-parton twist-3 pion distribution amplitudes, which are finite at the end point [22], the singularities in the B → π form factor become linear.…”

“…Hence, a reliable formalism for exclusive B meson decays must involve the parton transverse degrees of freedom. The effect due to the inclusion of k T has been explored thoroughly in [13][14][15], which also smears the end-point singularities in the heavy-to-light form factors [16]. In this paper we shall concentrate only on the Sudakov effect from threshold resummation, and neglect the k T dependence.…”

B0→ωη(′)andϕη(′Guo1, Chen2, Xiao3 2007Phys. Rev. D220140View full textAdd to dashboardCite

“…Here only the contribution of the Lorentz structure φ B (k 1 ) is taken into account, since the contribution of the second Lorentz structureφ B is numerically small [24,25] and has been neglected. For the distribution amplitude φ B in Eq.…”

“…This is the same wave functions as being used in Refs. [19,24], which is a best fit for most of the measured hadronic B decays.…”