Search for $D^0-{\bar D}^0$ Mixing Using Doubly Flavor Tagged Semileptonic Decay Modes

TL;DR

This paper searches for $D^0-\bar{D}^0$ mixing using semileptonic decay modes in electron-positron collision data, setting upper limits on the mixing rate with no significant evidence found.

Contribution

It introduces a novel method to detect $D^0-\bar{D}^0$ mixing via doubly flavor tagged semileptonic decays in $e^+e^-$ collisions, providing new constraints on mixing parameters.

Findings

Observed 3 mixed candidates vs. 2.85 background events

Set 68% confidence interval for mixing rate: (-5.6, 7.4) x 10^{-4}

Set 90% confidence interval for mixing rate: (-13, 12) x 10^{-4}

Abstract

We have searched for $D^0 - \bar{D}^0$ mixing in $D^{*+} \to \pi^+ D^0$ decays with $D^0 \to K^{(*)} e \nu$ in a sample of $e^+ e^- \to {c\bar c}$ events produced near 10.58 GeV. The charge of the slow pion from charged $D^*$ decay tags the charm flavor at production, and it is required to be consistent with the flavor of a fully reconstructed second charm decay in the same event. We observe 3 mixed candidates compared to 2.85 background events expected from simulation. We ascribe a 50% systematic uncertainty to this expected background rate. We find a central value for the mixing rate of $0.4 \times 10^{-4}$. Using a frequentist method, we set corresponding 68% and 90% confidence intervals at $(-5.6, 7.4) \times 10^{-4}$ and $(-13, 12) \times 10^{-4}$, respectively.