Measurement of D0-anti-D0 Mixing using the Ratio of Lifetimes for the Decays D0 --> K-pi+, K-K+, and pi-pi+

TL;DR

This paper reports a precise measurement of $D^0$-$ar{D^0}$ mixing parameters using lifetime ratios from different decay modes, providing evidence for mixing at the 3-sigma level with implications for CP violation.

Contribution

The study introduces a new measurement of $y_{CP}$ using lifetime ratios from multiple decay modes, improving the precision of $D^0$-$ar{D^0}$ mixing parameters with combined data from BaBar.

Findings

Evidence of $D^0$-$ar{D^0}$ mixing at 3 sigma

Measured $y_{CP} = 1.24 ext{%} ext{ with uncertainties}

Combined $y_{CP}$ result of 1.03% with improved precision

Abstract

We present a measurement of $D^0$-$\bar{D^0}$ mixing parameters using the ratios of lifetimes extracted from a sample of $D^0$ mesons produced through the process $D^{*+}\to\D^0\pi^+$, that decay to $K^{+}\pi^{-}$, K^{-}K^{+}$, or $\pi^-\pi^+$. The Cabibbo-suppressed modes $K^{-}K^{+}$ and $\pi^-\pi^+$ are compared to the Cabibbo-favored mode $K^{+}\pi^{-}$ to obtain a measurement of $y_{CP}$, which in the limit of CP conservation corresponds to the mixing parameter $y$. The analysis is based on a data sample of 384 $fb^{-1}$ collected by the $BaBar$ detector at the PEP-II asymmetric-energy $e^+e^-$ collider. We obtain $y_{CP} = [1.24\pm 0.39\mathrm{(stat)} \pm 0.13\mathrm{(syst)}]%$, which is evidence of $D^0$-$\bar{D^0}$ mixing at the $3\sigma$ level, and $\Delta Y = [-0.26\pm 0.36\mathrm{(stat)} \pm 0.08 \mathrm{(syst)}]%$, where $\Delta Y$ constrains possible CP violation. Combining this result with a previous $BaBar$ measurement of $y_{CP}$ obtained from a separate sample of $D^0\to K^{-}K^{+}$ events, we obtain $y_{CP} = [1.03\pm 0.33 \mathrm{(stat)} \pm 0.19 \mathrm{(syst)}]%$.