A Measurement of $\sin 2\beta$ from $B\to J/\psi K^0_S$ with the CDF detector

TL;DR

This paper presents an updated measurement of the CP violation parameter sin2 using data from the CDF detector, employing multiple tagging algorithms and a maximum likelihood fit, consistent with Standard Model predictions.

Contribution

It provides the first measurement of sin2 using the full Run I data sample from CDF with a novel combination of tagging methods.

Findings

Measured sin2 = 0.79 with uncertainties

Result consistent with Standard Model predictions

Uses a maximum likelihood fit with multiple tagging algorithms

Abstract

This paper reports an updated measurement of the Standard Model CP violation parameter $\sin2\beta$ using the CDF Detector at Fermilab. The entire Run I data sample of 110 pb$^{-1}$ of proton antiproton collisions at $\sqrt{s}=1.8 TeV$ is used to identify a signal sample of $\sim 400$ $B \to J/\psi K^0_S$ events, where $J/\psi \to \mu^+\mu^-$ and $K_S^0 \to \pi^+\pi^-$. 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 $\sin2\beta = 0.79 {+0.41\atop-0.44}$(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.