A measurement of B bar{B} mixing with the DELPHI detector at LEP

The data collected during 1990 and 1991 LEP runs with the DELPHI detector have been analyzed to measure the probability [chi] for a [ital B] meson to undergo mixing before decay. A study based on events containing two identified leptons lying on opposite detector sides yielded [chi]=0.121[plus minus][sub 0.040][sup 0.044](stat.)[plus minus]0.017(syst.); a comparison between the charge of a high [ital p][sub [ital t]] muon and the one of the jet recoiling in the opposite direction gave [chi]=0.075[plus minus]0.053 (stat. [direct sum] syst.); the combined result is [chi]=0.101[plus minus]0.035 (stat. [direct sum] syst.). No signal of CP violation has been observed.