This thesis describes a measurement of B0- B0 mixing in events produced by electron-positron annihilation at a center of mass energy of 29 GeV. The data were taken by the Mark II detector in the PEP storage ring at the Stanford Linear Accelerator Center between 1981 and 1987, and correspond to a total integrated luminosity of 224pb-1.
We used a new method, based on the kinematics of hadronic events containing two leptons, to provide a measurement of the probability, x, that a hadron, initially containing a b (b) quark decays to a positive (negative) lepton to be X = 0.17+0.15-0.08, with 90% confidence level upper and lower limits of 0.38 and 0.06, respectively, including all estimated systematic errors. Because of the good separation of signal and background, this result is relatively insensitive to various systematic effects which have complicated previous measurements.
We interpret this result as evidence for the mixing of neutral B mesons. Based on existing B0d mixing rate measurements, and some assumptions about the fractions of B0dand B0smesons present in the data, this result favors maximal mixing of B0smesons, although it cannot rule out zero B0smixing at the 90% confidence level.
