Rate Measurement of $D^{0}\to K^{+}\pi^{-}\pi^{0}$ and Constraints on $D^{0} - \overline{D^{0}}$ Mixing

TL;DR

This paper reports the first observation and measurement of the decay rate of D0 -> K+pi-pi0, providing insights into D0-D0bar mixing and CP asymmetry with significant statistical confidence.

Contribution

It presents the first measurement of the D0 -> K+pi-pi0 decay rate and constrains D0-D0bar mixing parameters using data from e+e- collisions near the Upsilon(4S).

Findings

Measured decay rate ratio: 0.0043 with statistical and systematic uncertainties.

Observed signal significance of 4.9 standard deviations.

CP asymmetry consistent with zero within uncertainties.

Abstract

We present an observation and rate measurement of the decay D0 -> K+pi-pi0 produced in 9/fb of e+e- collisions near the Upsilon(4S) resonance. The signal is inconsistent with an upward fluctuation of the background by 4.9 standard deviations. We measured the rate of D0 -> K+pi-pi0 normalized to the rate of D0bar -> K+pi-pi0 to be 0.0043 +0.0011 -0.0010 (stat) +/- 0.0007 (syst). This decay can be produced by doubly-Cabibbo-suppressed decays or by the D0 evolving into a D0bar through mixing, followed by a Cabibbo-favored decay to K+pi-pi0. We also found the CP asymmetry A=(8 +25 -22)% to be consistent with zero.