LEP measurements of Vcb and Vub

Abstract

The magnitude of the CKM matrix element Vcb has been measured using B° → D∗+l−ν decays recorded on the Z0 peak using the OPAL, ALEPH and DELPHI detectors at LEP. The D∗+ → d0π+ decays were reconstructed both in particular decay modes and via an inclusive technique. The product of ¦Vcb¦ and the decay form factor of the B° → D∗+l−ν transition at zero recoil. F(1) was measured to be F(1)¦Vcb¦=(35.6 ± 1.7) × 10−3. ¦Vcb¦ is obtained by using Heavy Quark Effective Theory calculations for F(1). The semi-leptonic branching ratio BR(b → dv) is also used to extract Vcb. The combined result is ¦Vcb¦ = (40.7 ± 1.9) × 10−3. The semi-leptonic branching ratio BR(b → ulv) is measured and used to extract the magnitude of Vub, ¦Vub¦ = (4.09−0.69+0.59) × 10−3.