Factorization and dispersion relations for radiative leptonic B decay

Autor(en)

Yu-Ming Wang

Abstrakt

Applying the dispersion approach we compute perturbative QCD corrections to the power suppressed soft contribution of B → γℓν at leading twist. QCD factorization for the B → γ

^* form factors is demonstrated explicitly for the hard-collinear transverse polarized photon at one loop, with the aid of the method of regions. While the one-loop hard function is identical to the matching coefficient of the QCD weak current ūγ

_{μ ⊥}(1 − γ

₅)b in soft-collinear effective theory, the jet function from integrating out the hard-collinear fluctuations differs from the corresponding one entering the factorization formula of B → γℓν, due to the appearance of an additional hard-collinear momentum mode. Furthermore, we evaluate the sub-leading power contribution to the B → γ form factors from the three-particle B-meson distribution amplitudes (DAs) at tree level, with the dispersion approach. The soft contribution to the B → γ form factors from the three-particle B-meson DAs is shown to be of the same power compared with the corresponding hard correction, in contrast to the two-particle counterparts. Numerically the next-to-leading-order QCD correction to the soft two-particle contribution in B → γ form factors will induce an approximately (10 ∼ 20)% shift to the tree-level contribution at λ

_B(μ

₀) = 354 MeV. Albeit of power suppression parametrically, the soft two-particle correction can decrease the leading power predictions for the B → γ form factors by an amount of (10 ∼ 30)% with the same value of λ

_B(μ

₀). Employing the phenomenological model of the three-particle B-meson DAs inspired by a QCD sum rule analysis, the three-particle contribution to the B → γ form factors is predicted to be of O(1%), at leading order in α

_s, with the default theory inputs. Finally, we explore theory constraints on the inverse moment of the leading-twist B-meson DA λ

_B from the recent Belle measurements of the partial branching fractions of B → γℓν, taking into account the newly computed contributions to the B → γ form factors at subleading power.

Organisation(en)

Teilchenphysik

Externe Organisation(en)

Nankai University

Journal

Journal of High Energy Physics

Band

2016

Anzahl der Seiten

33

ISSN

1029-8479

DOI

https://doi.org/10.1007/JHEP09(2016)159

Publikationsdatum

09-2016

Peer-reviewed

Ja

ÖFOS 2012

103012 Hochenergiephysik

Schlagwörter

ASJC Scopus Sachgebiete

Nuclear and High Energy Physics

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/4c3750f9-91b7-4e83-8ca0-b60ebe25a89f