MeasuringCPviolation in theB0B¯0system with asymmetric-energye+e−beams

We have studied in some detail the possibility of observing CP violation in the B-meson system using asymmetric-energy $e^{+}$ $e^{\mathrm{-}}$ beams colliding with a center-of-mass energy corresponding to the Υ(4S) mass. If a CP eigenstate is detected in conjunction with an identified $B^0$ or B${¯}^0$, the distribution of the flight path between decays contains a term which provides a measurement of CP violation, as discussed in this paper. The moving B mesons in the laboratory make this flight-path measurement possible. The use of the Υ(4S) provides the largest BB¯ cross section in $e^{+}$ $e^{\mathrm{-}}$ production, other than from the $Z^0$, and allows excellent background rejection because the B is monoenergetic in the center-of-mass frame. Since there are no extra fragmentation products accompanying the BB¯ in the event, very simple tagging strategies can be used to separate $B^0$ from B${¯}^0$ decays, providing a tagging efficiency close to 50%. The CP eigenstates studied in this paper are J/ψ+$K_S^0$, J/ψ+$K^{\mathrm{*}0}$ and ψ’+$K_S^0$. Given an adequate detector, the integrated luminosity needed to observe CP violation in the standard model is expected to be about 2×${10}^{40}$ ${\mathrm{cm}}^{\mathrm{-}2}$ or ${10}^7$ produced $B^0$B${¯}^0$ pairs.