We present an improved analysis of the constraints on the first two
Gegenbauer moments, a2π​ and a4π​, of the pion's leading-twist
distribution amplitude from a QCD light-cone sum rule analysis of B→π
weak transition form factor f+​(q2). Proper chiral current is adopted in
QCD light-cone sum rule so as to eliminate the most uncertain twist-3
contributions to f+​(q2), and then we concentrate our attention on the
properties of the leading-twist pion DA. A nearly model-independent f+​(q2)
as shown in Ref.\cite{pball0} that is based on the spectrum of B→πlν
decays from BaBar, together with their uncertainties, are adopted as the
standard shape for f+​(q2) to do our discussion. From a minimum χ2-fit
and by taking the theoretical uncertainties into account, we obtain
a2π​(1GeV)=0.17−0.17+0.15​ and a4π​(1GeV)=−0.06−0.22+0.20​
at the 1σ confidence level for mb∗​∈[4.7,4,8]GeV.Comment: 10 pages, 4 figures. References added. To be published in EPJ