Measurement of the CP-Violation Parameter $\sin(2β)$ in $B^0_d/\bar{B}{^0_d} \to J/ψK^0_S$ Decays

We present a measurement of the time-dependent asymmetry in the rate for $\bar{B}{^0_d}$ versus $B^0_d$ decays to $J/\psi K^0_S$. In the context of the Standard Model this is interpreted as a measurement of the CP-violation parameter $\sin(2\beta)$. A total of $198\pm 17$ $B^0_d/\bar{B}{^0_d}$ decays were observed in $p\bar{p}$ collisions at $\sqrt{s} = 1.8$ TeV by the CDF detector at the Fermilab Tevatron. The initial $b$-flavor is determined by a same side flavor tagging technique. Our analysis results in $\sin(2\beta) = 1.8\pm 1.1(stat)\pm 0.3(syst)$.