2005/05/31 by Benjamı́n Grinstein, Benjamin Grinstein, Dan Pirjol
Physics and Astronomy · #Black Holes and Theoretical Physics #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ph
paper · pdf · doi:10.1103/physrevd.73.094027
published as Phys.Rev. D73 (2006) 094027 · 16 pages, 5 figures. Version to appear in Physical Review D. One new observable introduced and considered - the slope of the zero of the forward-backward asymmetry as function of the Kπinvariant mass
arxiv created 2006/04/26 · openalex publication_date 2006/05/31 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We derive factorization relations for the transverse helicity amplitudes in B\ensuremath→K\ensuremathπ\ensuremathℓ+\ensuremathℓ^\ensuremath- at leading order in \ensuremathΛ/mb, in the kinematical region with an energetic kaon and a soft pion. We identify and compute a new contribution of leading order in \ensuremathΛ/mb to the B\ensuremath→K\ensuremathπ\ensuremathℓ+\ensuremathℓ^\ensuremath- amplitude which is not present in the one-body decay B\ensuremath→K*\ensuremathℓ+\ensuremathℓ^\ensuremath-. As an application we study the forward-backward asymmetry (FBA) of the lepton momentum angular distribution in B\ensuremath→K\ensuremathπ\ensuremathℓ+\ensuremathℓ^\ensuremath- decays on and off the K* resonance. The FBA in these decays has a zero at q02=q02(M_K\ensuremathπ), which can be used, in principle, for determining the Wilson coefficients C7,9 and testing the standard model. We point out that the slope of the q02(M_K\ensuremathπ2) curve contains the same information about the Wilson coefficients as the location of the zero, but is less sensitive to unknown nonperturbative dynamics. We estimate the location of the zero at leading order in factorization, and using a resonant model for the B\ensuremath→K\ensuremathπ\ensuremathℓ+\ensuremathℓ^\ensuremath- nonfactorizable amplitude.