Model-independent measurement of $D^0$-$\overline{D}{}^0$ mixing parameters in $D^0\rightarrow K^0_{S}\pi^+\pi^-$ decays at Belle and Belle II

TL;DR

This study measures $D^0$-$ar{D}^0$ mixing parameters in a model-independent way using large datasets from Belle and Belle II, providing results consistent with prior measurements.

Contribution

It introduces a model-independent method to determine $D^0$-$ar{D}^0$ mixing parameters using combined data from Belle and Belle II.

Findings

Measured mixing parameters: x = (4.0±1.7±0.4)×10^{-3}

Measured mixing parameters: y = (2.9±1.4±0.3)×10^{-3}

Results agree with previous measurements.

Abstract

We perform a model-independent measurement of the $D^0$-$\overline{D}{}^0$ mixing parameters using samples of $e^+e^-$-collision data collected by the Belle and Belle II experiments that have integrated luminosities of $951\ \text{fb}^{-1}$ and $408\ \text{fb}^{-1}$, respectively. Approximately $2.05\times10^6$ neutral $D$ mesons are reconstructed in the $D^0\rightarrow K^0_{S}\pi^+\pi^-$ channel, with the neutral $D$ flavor tagged by the charge of the pion in the $D^{*+}\rightarrow D^0\pi^+$ decay. Assuming charge-parity symmetry, the mixing parameters are measured to be $ x = (4.0\pm1.7\pm0.4)\times 10^{-3} $ and $ y = (2.9\pm1.4\pm0.3)\times 10^{-3}$, where the first uncertainties are statistical and the second systematic. The results are consistent with previous determinations.