Search for time-dependent $CP$ violation in $D^0 \rightarrow \pi^+ \pi^- \pi^0$ decays

TL;DR

This paper reports a search for time-dependent $CP$ violation in $D^0 ightarrow \pi^+\pi^-\pi^0$ decays using LHCb data, finding results consistent with no $CP$ violation, thus testing the Standard Model predictions.

Contribution

First measurement of time-dependent $CP$ violation in $D^0 ightarrow \pi^+\pi^-\pi^0$ decays with a large LHCb dataset, providing new constraints on $CP$ violation in charm decays.

Findings

Measured $\Delta Y$ consistent with zero

No evidence of $CP$ violation found

Results agree with Standard Model expectations

Abstract

A measurement of time-dependent $CP$ violation in $D^0 \rightarrow \pi^+ \pi^- \pi^0$ decays using a $pp$ collision data sample collected by the LHCb experiment in 2012 and from 2015 to 2018, corresponding to an integrated luminosity of 7.7$\,\mathrm{fb}^{-1}$, is presented. The initial flavour of each $D^0$ candidate is determined from the charge of the pion produced in the $D^*(2010)^+ \rightarrow D^0 \pi^+$ decay. The decay $D^0 \rightarrow K^- \pi^+ \pi^0$ is used as a control channel to validate the measurement procedure. The gradient of the time-dependent $CP$ asymmetry, $\Delta Y$, in $D^0 \rightarrow \pi^+ \pi^- \pi^0$ decays is measured to be \begin{equation*} \Delta Y = (-1.3 \pm 6.3 \pm 2.4) \times 10^{-4}, \end{equation*} where the first uncertainty is statistical and the second is systematic, which is compatible with $CP$ conservation.