Measurement of Bs-Bs-bar mixing

The study deals with a Monte Carlo simulation of Bs-Bs measurement through the collision of electrons and positrons having different energies. It also focuses on the feasibility of the determination of the mass difference parameter (xs=Δms/Γ), and the optimization of the degree of asymmetry in the beam energies. If the mass difference parameter is 6.0 or so, it would be very likely that the value of the parameter can be determined from a sufficient number of events that correspond to one-year data. If the parameter is larger, the following three factors, which are affected by the degree of the asymmetry in collision energy, will be involved: a decrease in acceptance due to deformation of the angular distribution of particles toward the front, a decrease in resolution due to deformation of the angular distribution of particles toward the front and increased material passage, and an increase in time resolution due to an enhanced boost of B. Of these, the third factor has the greatest effect, indicating that a large asymmetry is desirable, though the other two factors can have a significant effect if the asymmetry is extremely large. (N.K.)