Measurement of the B⁺ and B⁰ lifetimes and search for CP(T) violation using reconstructed secondary vertices

The lifetimes of the B⁺ and B⁰ mesons, and their ratio, have been measured in the OPAL experiment using 2.4 million hadronic Z⁰ decays recorded at LEP. Z⁰ → bb̄ decays were tagged using displaced secondary vertices and high momentum electrons and muons. The lifetimes were then measured using well-reconstructed charged and neutral secondary vertices selected in this tagged data sample. The results are τ_Β+ = 1.643 ± 0.037 ± 0.025 ps τ_Β0 = 1.523 ± 0.057 ± 0.053 ps τ_Β+/τ_Β0 = 1.079 ± 0.064 ± 0.041, where in each case the first error is statistical and the second systematic. A larger data sample of 3.1 million hadronic Z⁰ decays has been used to search for CP and CPT violating effects by comparison of inclusive b and b hadron decays. No evidence for such effects is seen. The CP violation parameter Re(∈_Β) is measured to be Re(∈_Β) = 0.001 ± 0.014 ± 0.003 and the fractional difference between b and b̄ hadron lifetimes is measured to be (Δτ/τ)_b ≡ τ(b hadron) - τ(b̄ hadron)/τ(average) = -0.001 ± 0.012 ± 0.008.