Charm mixing at LHCb

TL;DR

This paper reports the first observation of charm meson mixing at LHCb through a time-dependent analysis of $D^0$ decay rates, measuring mixing parameters with high significance using 1.0 fb$^{-1}$ of data.

Contribution

It provides the first single-measurement observation of charm mixing with precise determination of mixing parameters and significance.

Findings

Mixing parameters measured: $x'^2$ and $y'$ with uncertainties.

No-mixing hypothesis excluded at 9.1 sigma.

First observation of charm mixing from a single measurement.

Abstract

We report a measurement of the time-dependent ratio of $D^0\to K^+\pi^-$ to $D^0\to K^-\pi^+$ decay rates in $D^{*+}$-tagged events using 1.0\,fb$^{-1}$ of integrated luminosity recorded by the LHCb experiment. We measure the mixing parameters $x'^2=(-0.9\pm1.3)\times10^{-4}$, $y'=(7.2\pm2.4)\times10^{-3}$ and the ratio of doubly-Cabibbo-suppressed to Cabibbo-favored decay rates $R_D=(3.52\pm0.15)\times10^{-3}$. The result excludes the no-mixing hypothesis with a probability corresponding to 9.1 standard deviations and represents the first observation of charm mixing from a single measurement