Short-distance information from B(KL→μ+μ−)

A new analysis of the long-distance two-photon dispersive amplitude of KL→μ+μ− is presented. We introduce a phenomenological parameterization of the KL→γ∗γ∗ form factor, constrained at low energies by KL→γℓ+ℓ−(ℓ=e,μ) data and at high energies by perturbative QCD. Using this form factor we provide a reliable estimate of magnitude and relative uncertainty of the two-photon dispersive contribution to KL→μ+μ−. We finally discuss the implications of this analysis for the extraction of short-distance information from B(KL→μ+μ−).