A search for $\textit{ CP}$ violation in $D^{ 0} \rightarrow K_{ S}^{ 0} K^{ +} \pi^{ -} $ and $D^{ 0} \rightarrow K_{ S}^{ 0} K^{ -} \pi^{ +} $ decays is reported. The search is performed using an unbinned model-independent method known as the energy test that probes local $\textit{ CP}$ violation in the phase space of the decays. The data analysed correspond to an integrated luminosity of $5.4~$fb$^{ -1}$ collected in proton-proton collisions by the LHCb experiment at a centre-of-mass energy of $\sqrt{ s}=13$~TeV, amounting to approximately 950 thousand and 620 thousand signal candidates for the $D^{ 0} \rightarrow K_{ S}^{ 0} K^{ -} \pi^{ +} $ and $D^{ 0} \rightarrow K_{ S}^{ 0} K^{ +} \pi^{ -} $ modes, respectively. The method is validated using $D^{ 0} \rightarrow K^{ -} \pi^{ +} \pi^{ -} \pi^{ +} $ and $D^{ 0} \rightarrow K_{ S}^{ 0} \pi^{ +} \pi^{ -} $ decays, where $\textit{ CP}$-violating effects are expected to be negligible, and using background-enhanced regions of the signal decays. The results are consistent with $\textit{ CP}$ symmetry in both the $D^{ 0} \rightarrow K_{ S}^{ 0} K^{ -} \pi^{ +} $ and the $D^{ 0} \rightarrow K_{ S}^{ 0} K^{ +} \pi^{ -} $ decays, with $p$-values for the hypothesis of no $\textit{ CP}$ violation of 70% and 66%, respectively.
Categories: hep-ex