W-EXCHANGE AND W-ANNIHILATION PROCESSES OF B-MESONS

Using the PQCD method we calculate the W-exchange and the W-annihilati on processes of B mesons, which in general involve a charm quark or an ti-quark in the final state. The nonvanishing amplitudes of these proc esses are found to be suppressed by a factor of m(c)/m(b) compared to the tree or the time-like penguin processes, but some of them are with in the reach of observation at the future B-factories, and (B) over ba r (0)(d) --> Ds+K- whose branching ratio is found to be 6.6 x 10(-6) c an be found even before the B-factory era. Comparisons with the result s based on the BSW model are also given. (C) 1997 Published by Elsevie r Science B.V.