Eur. Phys. J. C (2008) 57: 665-669
https://doi.org/10.1140/epjc/s10052-008-0709-0

Regular Article - Theoretical Physics

Constraints on the leading-twist pion distribution amplitude from a QCD light-cone sum rule with chiral current

Department of Physics, Chongqing University, Chongqing, 400044, People’s Republic of China

^* e-mail: wuxg@cqu.edu.cn

Received: 20 June 2008
Revised: 26 July 2008
Published online: 10 September 2008

Abstract

We present an improved analysis of the constraints on the first two Gegenbauer moments, a ₂ ^π and a ₄ ^π , of the pion’s leading-twist distribution amplitude from a QCD light-cone sum rule analysis of the B→π weak transition form factor f ₊(q ²). A proper chiral current is adopted in QCD light-cone sum rules so as to eliminate the most uncertain twist-3 contributions to f ₊(q ²), and then we concentrate our attention on the properties of the leading-twist pionic DA. A nearly model-independent f ₊(q ²), based on the spectrum of B→π l ν decays from BaBar, together with uncertainties, is adopted as the standard shape for f ₊(q ²) for our discussion. From a minimum χ ²-fit and by taking the theoretical uncertainties into account, we obtain a ₂ ^π (1 GeV)=0.17 _−0.17 ^+0.15 and a ₄ ^π (1 GeV)=−0.06 _−0.22 ^+0.20 at the 1σ confidence level for m _b ^* ∈[4.7,4,8] GeV.