Measurement of $V_{cb}$ and $V_{ub}$ at LEP

DELPHI has measured V/sub ub//V/sub cb/ using semileptonic decays with secondary hadronic systems having masses below the D mass, enriched in b to ul nu transitions, and found the ratio to be 0.100+or-0.011(stat.)+or-0.018(syst.)+or-0.009(model). Combined with other LEP measurements, a V/sub ub/ of (4.05/sub -0.74//sup +0.62/) *10/sup -3/ is obtained. DELPHI has determined V/sub cb/ to (41.2+or-3.9)*10/sup -3/ from a B/sup 0/ to D/sup *+/l nu decay rate study close to D/sup *+/ zero recoil. The corresponding LEP averaged V/sub cb/ is (38.4+or-3.3)*10/sup -3/. From the LEP semileptonic B branching fraction, a V/sub cb/ of (40.75+or-2.08)*10/sup -3/ is obtained, giving a new LEP overall V/sub cb/ of (40.2+or-1.9)*10 /sup -3/. (12 refs).