Search for $CP$ violation in $D^0\to {\pi }^{-}{\pi }^{+}{\pi }^0$ decays at LHCb

The LHCb experiment has recorded the world’s largest sample of charmed meson decays. This paper presents a study of a $D^0$ meson decaying into a final state containing a neutral pion in LHCb. The search for $CP$ violation exploits a novel model-independent unbinned technique to assign a $p$-value for the no $CP$ violation hypothesis. With a data sample size exceeding that of previous measurements by almost an order of magnitude the world’s best sensitivity is obtained. The $p$-value of no CP violation hypothesis given data of $D^0\to {\pi }^{-}{\pi }^{+}{\pi }^0$ decay analysed is found to be $(2.6 \pm 0.5)\times 10^-2$.