Measurement of the neutral D meson mixing parameters in $D^0 \rightarrow K_S \pi^+\pi^-$ decays.

A model-independent measurement of the charm mixing parameters $x_D$ and $y_D$ in the $D^0 \rightarrow K_S \pi^+\pi^-$ decay mode is presented. The method uses ratios of yields in symmetric bins of the Dalitz plot and is binned in decay time. This is an alternative approach that does not require the knowledge of the phase-space model of the decay. It also preserves good sensitivity to $x_D$ and to the relative sign between $x_D$ and $y_D$. Charm mixing parameters are an important step to measuring CP violation in charm mixing. The measured values of the mixing parameters are $x_D = (1.89 \pm 0.43 \pm 0.21 \pm 0.51) \%$ and $y_D = (-2.59 \pm 1.36 \pm 1.13 \pm 3.12) \%$ where the uncertainties are statistical, systematic, and due to input parameters respectively.