Original scientific paper
The double radiative annihilation of the heavy-light fermion bound states
J. O. Egg
; Department of Physics, University of Oslo, N-0316 Oslo, Norway
Krešimir Kumerički
; Department of Physics, Faculty of Science, University of Zagreb, POB 331, Bijenička cesta 32, HR-10002 Zagreb, Croatia
Ivica Picek
; Department of Physics, Faculty of Science, University of Zagreb, POB 331, Bijenička cesta 32, HR-10002 Zagreb, Croatia
Abstract
We consider the double-radiative decays of heavy-light QED and QCD atoms, µ+e− → γγ and B¯0 s → γγ. Especially, we take under scrutiny contributions coming from operators that vanish on the free-quark mass shell. We show that by field redefinitions, these operators are converted into contact terms attached to the bound state dynamics. A net off-shell contribution is suppressed with respect to the effect of the well known flavour-changing magnetic-moment operator by the bound-state binding factor. The negligible off-shellness of the weakly-bound QED atoms becomes more relevant for strongly bound QCD atoms. We analyse this off-shellness in model-approaches to QCD, one of them enabling us to keep close contact to the related effect in QED. We also comment on the off-shell effect in the corresponding process B¯d → K∗γ, and discuss possible hindering of the claimed beyond-standardmodel discovery in this decay mode.
Keywords
bound state; off-shellness; flavour-changing transition; rare decays
Hrčak ID:
304059
URI
Publication date:
1.10.2001.
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