DOI 10.1007/s100520000471
Bound-state effects in
and
decays
J.O. Eeg1 - K. Kumericki2 - I. Picek2
1 Department of Physics, University of Oslo, 0316 Oslo, Norway
2 Department of Physics, Faculty of Science, University of Zagreb,
P.O.B. 331, 10002 Zagreb, Croatia
Received: 7 April 2000 / Revised version: 10 May 2000 /
Published online: 9 August 2000 - © Springer-Verlag 2000
Abstract
We demonstrate that in the double-radiative decays of heavy-light
QED and QCD atoms,
and
,
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.
Copyright Società Italiana di Fisica, Springer-Verlag 2000