|Vub| and constraints on the leading-twist pion distribution amplitude from B→πℓν

Using new experimental data on the leptonic mass spectrum of B→πℓν, we simultaneously determine |Vub| and constrain a2π and a4π, the first two Gegenbauer moments of the pion's leading-twist distribution amplitude. We find |Vub|=(3.2±0.1±0.1±0.3)×10−3, where the first error is experimental, the second comes from the shape of the form factor in q2 and the third is a 8% uncertainty from the normalisation of the form factor. We also find a2π(1GeV)=0.19±0.19 and a4π(1GeV)⩾−0.07.