Search for CP violation in the phase space of D⁰ KS⁰K^ ^ decays with the energy test

A bstract A search for CP violation in D⁰ KS⁰K^+^- D 0 → K S 0 K + π − and D⁰ KS⁰K^-^+ D 0 → K S 0 K − π + decays is reported. The search is performed using an unbinned model-independent method known as the energy test that probes local 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 s s = 13 TeV, amounting to approximately 950 thousand and 620 thousand signal candidates for the D⁰ KS⁰K^-^+ D 0 → K S 0 K − π + and D⁰ KS⁰K^+^- D 0 → K S 0 K + π − modes, respectively. The method is validated using D 0 → K − π + π − π + and D⁰ KS⁰^+^- D 0 → K S 0 π + π − decays, where CP -violating effects are expected to be negligible, and using background-enhanced regions of the signal decays. The results are consistent with CP symmetry in both the D⁰ KS⁰K^-^+ D 0 → K S 0 K − π + and the D⁰ KS⁰K^+^- D 0 → K S 0 K + π − decays, with p -values for the hypothesis of no CP violation of 70% and 66%, respectively.