We present a measurement of the time-dependent asymmetry in the rate for ${\overline{B}}_d^0$ versus $B_d^0$ decays to $J/\psi K_S^0$. A nonzero asymmetry would be an indication of $\mathrm{CP}$ violation, and within the standard model this may be used to measure the $\mathrm{CP}$-violation parameter $\sin \left(2\beta \right)$. A total of $198\pm 17$ $B_d^0/{\overline{B}}_d^0$ decays were observed in $p\overline{p}$ collisions at $\sqrt{s}=1.8\mathrm{}\mathrm{TeV}$ by the CDF detector at the Fermilab Tevatron. $B_d^0$ and ${\overline{B}}_d^0$ are distinguished by a technique based on charge correlations from hadronization of the $b$ quark. Our analysis results in $\sin \left(2\beta \right)=1.8\mathrm{}\pm 1.1\left(\mathrm{stat}\right)\pm 0.3\left(\mathrm{syst}\right)$.

• Received 23 June 1998

DOI:https://doi.org/10.1103/PhysRevLett.81.5513