CHIRAL-SYMMETRY BREAKING, DUALITY IN THE (Q)OVER-BAR-Q CHANNEL AND B-](C)OVER-BAR-CS DECAYS

We address the issue of the quark-hadron duality in the spectral densi ties induced by the heavy-light quark currents (Q) over bar q. In the limit m(Q) --> infinity, m(q) --> 0 we observe an enhancement of the p hysical spectral density compared to the quark one in the scalar and a xial channels, due to the Goldstone meson contributions. This may impl y that the scale where duality sets in is higher in these channels tha n in the vector (pseudoscalar) case. Implications for the non-leptonic decays of B mesons (the b --> (c) over bar cs transition) are conside red. We discuss in detail the decay pattern and obtain an independent estimate of the ''wrong''-sign D yield. (C) 1997 Elsevier Science B.V.