Measurement of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">sin</mml:mi><mml:mi/><mml:mn>2</mml:mn><mml:mi>β</mml:mi></mml:math>from<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mrow><mml:mover><mml:mrow><mml:mi>B</mml:mi></mml:mrow><mml:mrow><mml:mo>→</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:mrow><mml:mi>J</mml:mi><mml:mo>/</mml:mo><mml:mi>ψ</mml:mi><mml:mrow><mml:msubsup><mml:mrow><mml:mi>K</mml:mi></mml:mrow><mml:mrow><mml:mi>S</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msubsup></mml:mrow></mml:math>with the CDF detector

This paper reports an updated measurement of the standard model $\mathrm{CP}$ violation parameter $\mathrm{sin}2\ensuremath{\beta}$ using the CDF Detector at Fermilab. The entire run I data sample of $110 {\mathrm{pb}}^{\ensuremath{-}1}$ of proton-antiproton collisions at $\sqrt{s}=1.8 \mathrm{TeV}$ is used to identify a signal sample of $\ensuremath{\sim}400 \stackrel{\ensuremath{\rightarrow}}{B}J/\ensuremath{\psi}{K}_{S}^{0}$ events, where $J/\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\psi}}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ and ${K}_{S}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}.$ The flavor of the neutral B meson is identified at the time of production by combining information from three tagging algorithms: a same-side tag, a jet-charge tag, and a soft-lepton tag. A maximum likelihood fitting method is used to determine $\mathrm{sin}2\ensuremath{\beta}{=0.79}_{\ensuremath{-}0.44}^{+0.41}(\mathrm{stat}+\mathrm{syst}).$ This value of $\mathrm{sin}2\ensuremath{\beta}$ is consistent with the standard model prediction, based upon existing measurements, of a large positive $\mathrm{CP}$-violating asymmetry in this decay mode.