The longitudinal muon polarization in KL → μ+μ-

Abstract

From a leading-order calculation of K10 → γ*γ* → ℓ+ℓ- in chiral perturbation theory, the longitudinal muon polarization in the decay KL → μ+μ- is found to be approximately 2 × 10-3 in the standard model. The relative branching ratios Λ(KS → ℓ+ℓ-) Λ(KS → 2γ) are predicted as 2 × 10-6 (ℓ = μ) and 8 × 10-9 (ℓ = e), respectively. © 1991.