Search for D^0-D^0bar mixing in D^0 -> K+pi- decays and measurement of the doubly-Cabibbo-suppressed decay rate

TL;DR

This study searches for D0-D0bar mixing by analyzing decay-time distributions of D0->K+pi- decays using Belle data, providing limits on mixing parameters and measuring the doubly-Cabibbo-suppressed decay rate.

Contribution

First measurement of D0-D0bar mixing parameters and decay rate using a large Belle dataset, including CP violation considerations.

Findings

No significant mixing observed within 95% confidence level.

Measured R_D = (0.381 1.7+0.8-1.6)%.

Established constraints on mixing parameters x' and y'.

Abstract

We have searched for mixing in the D0-D0bar system by measuring the decay-time distribution of D0->K+pi- decays. The analysis uses 90 fb^{-1} of data collected by the Belle detector at the KEKB e+e- collider. We fit the decay-time distribution for the mixing parameters x' and y' and also for the parameter R_D, which is the ratio of the rate for the doubly-Cabibbo-suppressed decay D0->K+pi- to that for the Cabibbo-favored decay D0->K-pi+. We do these fits both assuming CP conservation and allowing for CP violation. We use a frequentist method to obtain a 95% C.L. region in the x'^2 - y' plane. Assuming no mixing, we measure R_D = (0.381 \pm 0.017 +0.008 -0.016) %.