QUARK OFF-SHELL EFFECTS IN B-]GAMMA-GAMMA-DECAYS

We demonstrate that in the decay of a heavy-light quark system, like t he process B(s) --> gammagamma under consideration, there is an import ant contribution coming from operators that vanish on the free quark m ass-shell. Although numerical estimates are model-dependent, the signi ficance of genuine off-shell effects is quite general, and independent of the details of the boundstate dynamics. Such contributions will ty pically be somewhat smaller, but still significant in magnitude compar ed with the contribution from the standard off-diagonal, b --> sgamma magnetic-moment operator.