Measurement of the CP-Violation Parameter $\sin (2\beta )$ in $B_d^0/\bar{B}{}_d^0\to J/\psi K_S^0$ Decays

Abstract

We present a measurement of the time-dependent asymmetry in the rate for $\bar{B}{}_d^0$ versus $B_d^0$ decays to $J/\psi K_S^0$. In the context of the Standard Model this is interpreted as a measurement of the CP-violation parameter $\sin (2\beta )$. A total of $198\pm 17$ $B_d^0/\bar{B}{}_d^0$ 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 $\sin (2\beta )=1.8\pm 1.1(stat)\pm 0.3(syst)$.