Additional evidence for B0B̄0 mixing

Abstract The rate of like-charge dimuons has been measured with the MAC detector in hardonic events produced in e + e − annihilation at √ s =29 GeV. If the observed excess is attributed to B 0 B 0 mixing, the corresponding value of the mixing parameter χ = Γ (B→ μ − X)/ Γ (B→ μ ± X) is χ =0.21 +0.29 −0.15 and χ >0.02 at 90% CL.