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Structure-Dependent QED Effects in Exclusive B Decays at Subleading Power

Claudia Cornella, Matthias König, Matthias Neubert

Abstract

We derive a factorization theorem for the structure-dependent QED effects in the weak exclusive process $B^-\to\ell^-\barν_\ell$, i.e., effects probing the internal structure of the $B$ meson. The derivation requires a careful treatment of endpoint-divergent convolutions common to subleading-power factorization formulas. We find that the decay amplitude is sensitive to two- and three-particle light-cone distribution amplitudes of the $B$ meson as well as to a new hadronic parameter $F(μ,Λ)$, which generalizes the notion of the $B$-meson decay constant in the presence of QED effects. This is the first derivation of a subleading-power factorization theorem in which the soft functions are non-perturbative hadronic matrix elements.

Structure-Dependent QED Effects in Exclusive B Decays at Subleading Power

Abstract

We derive a factorization theorem for the structure-dependent QED effects in the weak exclusive process , i.e., effects probing the internal structure of the meson. The derivation requires a careful treatment of endpoint-divergent convolutions common to subleading-power factorization formulas. We find that the decay amplitude is sensitive to two- and three-particle light-cone distribution amplitudes of the meson as well as to a new hadronic parameter , which generalizes the notion of the -meson decay constant in the presence of QED effects. This is the first derivation of a subleading-power factorization theorem in which the soft functions are non-perturbative hadronic matrix elements.
Paper Structure (1 section, 24 equations, 1 figure)

This paper contains 1 section, 24 equations, 1 figure.

Table of Contents

  1. Acknowledgments.

Figures (1)

  • Figure 1: SCET-1 loop diagrams generating structure-dependent QED corrections. The up-quark and muon leaving the weak-interaction operator carry fractions $x$ and $\bar{x}=1-x$ of the large component $\bar{n}\cdot p_\ell$ of the muon momentum. The resulting contributions involve convolutions with a two-particle (left) and three-particle (right) LCDA of the $B$ meson.