Structure-dependent QED in B⁻→ ⁻ν̄(γ )

A bstract Based on explicitly gauge invariant interpolating operators we compute complete next-leading order QED-corrections for leptonic decays. These are sizeable since the helicity-suppression in V-A interactions allows for structure-dependent collinear logs. We have explicitly checked that these logs are absent for helicity-unsuppressed Yukawa-type transitions. Based on B → γ form factors we present the rates for B⁻→ (μ⁻,τ⁻)ν̄(γ ) B − → μ − τ − ν ¯ γ in differential and integrated form as a function of the photon energy cut-off Eγᶜᵘᵗ E γ cut . The effect of the virtual structure-dependent corrections are approximately +5% and +3% for the μ - and τ -channel respectively. The structure dependence of the real radiation exceeds that of the virtual one for .Eγᶜᵘᵗ|μ E γ cut μ > 0 . 18(3) GeV and is subdominant for the tau channel even when fully inclusive.