TREE-LEVEL LONG-DISTANCE CONTRIBUTIONS TO K+→π+ ℓ+ℓ-

Abstract

We study a new contribution, which is a tree-level transition from long-distance dynamics, to K+→π+ℓ+ℓ- (ℓ = e, μ) decays. It is found that this tree-diagram can be calculated unambiguously and would generate the additional contribution to the vector, axial-vector, scalar and pseudoscalar form factor of the decay. Our analysis shows that these form factors are strongly suppressed and this long-distance contribution is well under control.