Extracting the CP-conserving and CP-violating form factors of KL → γγ, KS → γγ, and π0 → γγ from the decays of KL, KS and π0 into two identical pairs of leptons
Department of Physics, Millersville University, Millersville, PA 17551, USA
Published online: 14 December 2001
The extractions of the CP-conserving and CP-violating form factors of the decays of the long-lived kaon KL and the short-lived kaon KS into two photons from the branching ratios of KSL → γγ and KSL → γγ → l-l+l-l+, where l represents either an electron or a muon, are described. Using the currently available measurements of the branching ratios of KL → γγ and KL → e-e+e-e+ and assuming that the form factors are constants, the ratio of the CP-violating decay rate to the CP-conserving decay rate for KL → γγ is calculated to be 2.51% and the predicted branching ratio for KL → γγ → μ- μ+ μ- μ+ is 6.07 × 10-13. For KS → γγ, a measurement of the branching ratio of KS → γγ → e-e+e-e+ is needed to determine the ratio of the CP-violating decay rate to the CP-conserving decay rate and to accurately predict the branching ratio of KS → γγ → μ- μ+ μ- μ+. In the limit of complete CP-conservation the branching ratios are evaluated to be 4.39 × 10-10 for KS → γγ → e-e+e-e+ and 6.96 × 10-15 for KS → γγ → μ- μ+ μ- μ+. In a similar model where the form factors of π0γγ vertex are constants, the CP-violating decay rate component in π0 → γγ is shown, based on current available experimental data, to be less than 1% of the total decay rate.The magnitudes of the form factors are obtained by correlating the processes π0 → γγ and π0 → γγ → e-e+e-e+.
© Società Italiana di Fisica, Springer-Verlag, 2002