Subleading-power corrections to the radiative leptonic B -> gamma lv decay in QCD

Yu-Ming Wang, Yue-Long Shen

Applying the method of light-cone sum rules with photon distribution amplitudes, we compute the subleading-power correction to the radiative leptonic B -> gamma lv from the twist-two hadronic photon contribution at next-to-leading order in QCD; and further evaluate the higher-twist "resolved photon" corrections at leading order in as, up to twist-four accuracy. QCD factorization for the vacuum-to-photon correlation function with an interpolating current for the B-meson is established explicitly at leading power in A/m(b) employing the evanescent operator approach. Resummation of the parametrically large logarithms of m(b)(2)/Lambda(2) entering the hard function of the leading-twist factorization formula is achieved by solving the QCD evolution equation for the light-ray tensor operator at two loops. The leading-twist hadronic photon effect turns out to preserve the symmetry relation between the two B -> gamma form factors due to the helicity conservation, however, the higher-twist hadronic photon corrections can yield symmetry-breaking effect already at tree level in QCD. Using the conformal expansion of photon distribution amplitudes with the non-perturbative parameters estimated from QCD sum rules, the twist-two hadronic photon contribution can give rise to approximately 30% correction to the leading-power "direct photon" effect computed from the perturbative QCD factorization approach. In contrast, the subleading-power corrections from the higher-twist two-particle and three-particle photon distribution amplitudes are estimated to be of O(3 similar to 5%) with the light-cone sum rule approach. We further predict the partial branching fractions of B -> gamma lv with a photon energy cut E gamma >= E-cut, which are of interest for determining the inverse moment of the leading-twist B-meson distribution amplitude thanks to the forthcoming high -luminosity Belle II experiment at KEK.

Particle Physics
External organisation(s)
Nankai University, Ocean University of China
Journal of High Energy Physics
No. of pages
Publication date
Peer reviewed
Austrian Fields of Science 2012
103012 High energy physics
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