Heavy-to-light decays at large recoil: Systematic treatment of short- and long-distance QCD effects

TL;DR

The paper develops a Soft-Collinear Effective Theory (SCET) framework for heavy-to-light decays at large recoil, enabling a systematic factorization of short-distance QCD effects from long-distance hadronic physics. It derives the effective Lagrangian and heavy-quark current including 1/m power corrections, and applies the formalism to heavy-to-light form factors, highlighting spin/helicity symmetry reductions at leading order and the structure of power corrections. The analysis clarifies how form factors factorize into hard coefficients and soft functions, and discusses the status of hard spectator scattering within EFT. The work provides a principled basis for reducing theoretical uncertainties in B decays and for confronting predictions with experimental data.

Abstract

Heavy quark decays into energetic, collinear quarks and gluons are discussed within an effective theory that accomplishes the factorization of soft and hard strong interaction effects. We derive the relevant effective Lagrangian, and perform the matching of the heavy quark current, including power corrections of order 1/m, where m is the heavy quark mass. We apply our framework to heavy-to-light form factors.

Figures (1)

• Figure 1: Heavy quark decay into collinear and ultra-soft particles.