Measurement ofsin2βfromB→J/ψKS0with the CDF detector

This paper reports an updated measurement of the standard model CP violation parameter sin 2{beta} using the CDF Detector at Fermilab. The entire run I data sample of 110 pb{sup -1} of proton-antiproton collisions at {radical}(s)=1.8 TeV is used to identify a signal sample of {approx}400 B{yields}J/{psi} K{sub S}{sup 0} events, where J/{psi}{yields}{mu}{sup +}{mu}{sup -} and K{sub S}{sup 0}{yields}{pi}{sup +}{pi}{sup -}. 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 sin 2{beta}=0.79{sub -0.44}{sup +0.41}(stat+syst). This value of sin 2{beta} is consistent with the standard model prediction, based upon existing measurements, of a large positive CP-violating asymmetry in this decay mode. (c) 2000 The American Physical Society.