A determination of the CP violation parameter $\eta_{+-}$ from the decay of strangeness-tagged neutral kaons

We report a measurement of the CP violation parameter $\eta$ from the time-dependent asymmetry between the decay rates of initially tagged \kn\ and \knb . The results are based on the complete data sample collected by the CPLEAR collaboration. With $\dm = (530.1 \pm 1.4) \times 10^{7}\hbar s^{-1}$ and $\ts = (89.32 \pm 0.08)$ ps, the values obtained are $\mita = (2.264 \pm 0.023_\mathrm{{stat}} \pm 0.026_\mathrm{{syst}} \pm 0.007_{\ts}) \times 10^{-3}$ and $\fas = 43.19^{\circ} \pm 0.53^{\circ}_\mathrm{{st at}} \pm 0.28^{\circ}_\mathrm{{syst}} \pm 0.42^{\circ}_{\dm}$.