A measurement of the B ⁰_d oscillation frequency using leptons and D*^± mesons

Abstract

Data collected with the OPAL detector during 1990–1994 are used to measure the time dependence of$B_d^0 \leftrightarrow \bar B_d^0$ mixing. A sample of 348 D*^± candidates with a lepton in the opposite hemisphere are reconstructed, of which 167±25 are expected to be from B ⁰_d decays. The B ⁰_d oscillation frequency is measured to be

$$\Delta m_d = 0.567 \pm 0.089(stat)_{ - 0.023}^{ + 0.029} (syst) ps^{ - 1} .$$

. A previously published analysis ofΔm _d using D*^± and lepton candidates in the same hemisphere and jet charge is also updated with a larger data sample. From 1200 D*^±ℓ^∓ candidates, of which 778±84 are expected to be from B ⁰_d decays, we find a value of:

$$\Delta m_d = 0.539 \pm 0.060(stat) \pm 0.024(syst) ps^{ - 1} .$$

. The combined result of these two analyses is

$$\Delta m_d = 0.548 \pm 0.050(stat)_{ - 0.019}^{ + 0.023} (syst) ps^{ - 1} .$$

.