engleski

Bound-state effects in mu+ e- -> gamma gamma and anti-B0(s) -> gamma gamma decays

We demonstrate that in the double-radiative decays of heavy-light QED and QCD atoms, \mu^{+} e^{-} \to \gamma\gamma and \bar{B}^{0}_{s} \to \gamma\gamma, there is a contribution coming from operators that vanish on the free-quark mass shell. This off-shell effect is suppressed with respect to the effect of the well known flavour-changing magnetic-moment operator by the bound-state binding factor. Accordingly, the negligible off-shellness of the weakly bound QED atoms becomes important for strongly bound QCD atoms. We present this effect in two different model-approaches to QCD, one of them enabling us to keep close contact to the related effect in QED.

radiative decays; flavour-changing operators; off-shell effects

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