Precision calculations of $B_{d, s} \to \pi, K$ decay form factors in soft-collinear effective theory

TL;DR

This paper enhances QCD calculations of $B_{d, s} o ext{pi, K}$ form factors at large recoil using SCET, incorporating next-to-leading-logarithmic resummation and subleading-power corrections for more precise theoretical predictions.

Contribution

It introduces a comprehensive method to include subleading-power corrections and resummation effects in SCET-based calculations of heavy-to-light form factors, improving accuracy.

Findings

Improved form factor predictions with resummation and subleading corrections.

Quantified impact of higher-twist and off-light-cone contributions.

Provided refined numerical results for semileptonic decay form factors.

Abstract

We improve QCD calculations of the $B_{d, s} \to \pi, K$ form factors at large hadronic recoil by implementing the next-to-leading-logarithmic resummation for the obtained leading-power light-cone sum rules in the soft-collinear effective theory (SCET) framework. Additionally, we endeavour to investigate a variety of the subleading-power contributions to these heavy-to-light form factors at ${\cal O}(\alpha_s^0)$, by including the higher-order terms in the heavy-quark expansion of the hard-collinear quark propagator, by evaluating the desired effective matrix element of the next-to-leading-order term in the ${\rm SCET_{I}}$ representation of the weak transition current, by taking into account the off-light-cone contributions of the two-body heavy-quark effective theory matrix elements as well as the three-particle higher-twist corrections from the subleading bottom-meson light-cone distribution amplitudes, and by computing the twist-five and twist-six four-body higher-twist effects with the aid of the factorization approximation. Having at our disposal the SCET sum rules for the exclusive $B$-meson decay form factors, we further explore in detail numerical implications of the newly computed subleading-power corrections by employing the three-parameter model for both the leading-twist and higher-twist $B$-meson distribution amplitudes. Taking advantage of the customary Bourrely-Caprini-Lellouch parametrization for the semileptonic $B_{d, s} \to \pi, K$ form factors, we then determine the correlated numerical results for the interesting series coefficients, by carrying out the simultaneous fit of the exclusive $B$-meson decay form factors to both the achieved SCET sum rule predictions and the available lattice QCD results.