KS→γγ,KL→π0γγand unitarity

Joachim Kambor, Barry R. Holstein
1994 Physical Review D, Particles and fields  
Agreement between the experimental value Γ (K_S→γγ) and the number predicted via a one-loop chiral perturbation theory calculation has been cited as a success for the latter. On the other hand the one-loop prediction for the closely related process K_L→π^0γγ has been found to be a factor three below the experimental value. Using the inputs of unitarity and dispersion relations, we demonstrate the importance of higher order loop effects to both of these processes.
doi:10.1103/physrevd.49.2346 pmid:10017223 fatcat:okwbcv5najeanmzhltcr5sijia