Measurement of $D^0-{\overline{D}}^0$ mixing and search for $CP$ violation with $D^0\to K^{+}{\pi }^{-}$ decays

Abstract

A measurement of the time-dependent ratio of the $D^0\to K^{+}{\pi }^{-}$ to ${\overline{D}}^0\to K^{+}{\pi }^{-}$ decay rates is reported. The analysis uses a sample of proton-proton collisions corresponding to an integrated luminosity of 6 fb${}^{-1}$ recorded by the LHCb experiment from 2015 through 2018 at a center-of-mass energy of 13 TeV. The $D^0$ meson is required to originate from a $D^{\ast +}\to D^0{\pi }^{+}$ decay, such that its flavor at production is inferred from the charge of the accompanying pion. The measurement is performed simultaneously for the $K^{+}{\pi }^{-}$ and $K^{-}{\pi }^{+}$ final states, allowing both mixing and $CP$-violation parameters to be determined. The value of the ratio of the decay rates at production is determined to be $R_{K\pi }=(343.1\pm 2.0)\times 10^{-5}$. The mixing parameters are measured to be $c_{K\pi }=(51.4\pm 3.5)\times 10^{-4}$ and $c_{K\pi }^{\prime }=(13\pm 4)\times 10^{-6}$, where $\sqrt{R_{K\pi }}{c}_{K\pi }$ is the linear coefficient of the expansion of the ratio as a function of decay time in units of the $D^0$ lifetime, and $c_{K\pi }^{\prime }$ is the quadratic coefficient, both averaged between the $K^{+}{\pi }^{-}$ and $K^{-}{\pi }^{+}$ final states. The precision is improved relative to the previous best measurement by approximately 60%. No evidence for $CP$ violation is found.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/1800

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Cited by in corpus (1)

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