Lattice predictions and comparison with experimental data for the radiative kaon decays K+→ℓ+νℓγ and K+→ℓ+νℓℓ′+ℓ′−

Abstract

Abstract K + → ℓ + ν ℓ γ and K + → ℓ + ν ℓ ℓ ′ + ℓ ′ − decays are characterized by the emission from the kaon of either a real or virtual photon, respectively. The nonperturbative interaction of the photon with the internal hadronic structure of the decaying meson is described by suitable form factors. With the huge improvement in the precision of lattice QCD results, increasingly QED corrections are included and in this work we review the latest lattice QCD predictions for the form factors and/or branching ratios of those processes. Moreover, we compare those predictions with existing experimental results. The comparison provides some interesting puzzles suggesting possible signs of new physics and motivates future improvements on both the theoretical and experimental determinations of the relevant form factors.