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Quark off-shell contributions to KL→γγ in a bound-state approach

We present a new piece of evidence in favour of the importance of the quark off-shellness in the kaon. The matrix elements of the flavour-changing operators for KL→γγ comply with the general behaviour of the matrix elements expected in the pairing bound-state model used here. The present calculation in essence agrees with previous chiral-quark results. The off-shell contribution turns out to be dominant (the model on-shell amplitude being at the 10% level). Compared with the chiral perturbation-theory approach, our off- shell contribution is an entirely new O(p4) {;\em direct-decay}; piece, whereas the non-diagonal magnetic-moment term belongs to the order O(p6).

High energy physics ; Experimental particle physics ; LHC ; CMS ; Hadron-Hadron scattering (experiments) ; Higgs physics ; p p: colliding beams ; Higgs particle: pair production ; bottom: 2 ; p p: scattering ; Higgs particle: coupling ; Higgs particle: hadroproduction ; Higgs particle: decay modes ; bottom: pair production ; photon: pair production ; top: pair production ; coupling: Yukawa ; coupling constant: upper limit ; vector boson: fusion ; mass spectrum: two-photon ; Standard model

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