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

Abstract Using new experimental data on the leptonic mass spectrum of B → π l ν , we simultaneously determine | V u b | and constrain a 2 π and a 4 π , the first two Gegenbauer moments of the pion's leading-twist distribution amplitude. We find | V u b | = ( 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 q 2 and the third is a 8% uncertainty from the normalisation of the form factor. We also find a 2 π ( 1 GeV ) = 0.19 ± 0.19 and a 4 π ( 1 GeV ) ⩾ − 0.07 .