QCD corrections to B→π form factors from light-cone sum rules

Wang, Yu-Ming (Physik Department T31, Technische Universität München, James-Franck-Straße 1, Garching, D-85748, Germany) ; Shen, Yue-Long (College of Information Science and Engineering, Ocean University of China, Qingdao, Shandong, 266100, PR China)

24 July 2015

Abstract: We compute perturbative corrections to B→π form factors from QCD light-cone sum rules with B -meson distribution amplitudes. Applying the method of regions we demonstrate factorization of the vacuum-to- B -meson correlation function defined with an interpolating current for pion, at one-loop level, explicitly in the heavy quark limit. The short-distance functions in the factorization formulae of the correlation function involves both hard and hard-collinear scales; and these functions can be further factorized into hard coefficients by integrating out the hard fluctuations and jet functions encoding the hard-collinear information. Resummation of large logarithms in the short-distance functions is then achieved via the standard renormalization-group approach. We further show that structures of the factorization formulae for fBπ+(q2) and fBπ0(q2) at large hadronic recoil from QCD light-cone sum rules match that derived in QCD factorization. In particular, we perform an exploratory phenomenological analysis of B→π form factors, paying attention to various sources of perturbative and systematic uncertainties, and extract |Vub|=(3.05−0.38+0.54|th.±0.09|exp.)×10−3 with the inverse moment of the B -meson distribution amplitude ϕB+(ω) determined by reproducing fBπ+(q2=0) obtained from the light-cone sum rules with π distribution amplitudes. Furthermore, we present the invariant-mass distributions of the lepton pair for B→πℓνℓ ( ℓ=μ,τ ) in the whole kinematic region. Finally, we discuss non-valence Fock state contributions to the B→π form factors fBπ+(q2) and fBπ0(q2) in brief.

Published in: Nuclear Physics B (2015)