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FIZIKA B 10 (2001) 4, 285-306
 
THE DOUBLE RADIATIVE ANNIHILATION OF THE HEAVY-LIGHT FERMION BOUND
STATES
J. O. EEGa, KREŠIMIR KUMERIČKIb and IVICA PICEKb
aDepartment of Physics, University of Oslo, N-0316 Oslo,
Norway
bDepartment of Physics, Faculty of Science, University of
Zagreb, POB 331,
Bijenička cesta 32, HR-10002 Zagreb, Croatia
E-mail addresses:
j.o.eeg@fys.uio.no, kkumer@phy.hr, picek@phy.hr
Dedicated to Professor Kseno Ilakovac on the occasion of his 70th
birthday
Received 29 March 2001; Accepted 15 October 2001
Online 6 April 2002
We consider the double-radiative decays of heavy-light QED and QCD atoms, m+ e- ® gg and [`B]0s
®gg. 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* g, and discuss
possible hindering of the claimed beyond-standard-model discovery in this decay mode.
PACS numbers: 14.60.Ef, 14.40.Nd, 12.15.Mn, 12.15.-y, 13.10.+q
UDC 539.126
Keywords: bound state, off-shellness, flavour-changing transition, rare decays
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