Precise determination of the branching ratio of the neutral-pion Dalitz decay

We provide a new value for the ratio R=Γ(π0→e+e−γ(γ))/Γ(π0→γγ)=11.978(6)×10^−3, which is by 2 orders of magnitude more precise than the current Particle Data Group average. It is obtained using the complete set of the next-to-leading-order radiative corrections in the QED sector, and incorporates up-to-date values of the π0-transition-form-factor slope. The ratio R translates into the branching ratios of the two main π0 decay modes: B(π0→γγ)=98.8131(6)% and B(π0→e+e−γ(γ))=1.1836(6)%.