Measurement of CP asymmetry in $ {D}^0\to {K}_{\textrm{S}}^0{K}_{\textrm{S}}^0 $ decays with Run 3 data

A measurement of CP asymmetry in ${D}^0\to {K}_{\textrm{S}}^0{K}_{\textrm{S}}^0$ decays is reported, based on a data sample of proton-proton collisions collected with the LHCb detector in 2024 at a centre-of-mass energy of 13.6 TeV, corresponding to an integrated luminosity of 6.2 fb − 1 . The ${D}^0\to {K}_{\textrm{S}}^0{\pi}^{+}{\pi}^{-}$ decay is used as calibration channel to cancel residual detection and production asymmetries. The time-integrated CP asymmetry for the ${D}^0\to {K}_{\textrm{S}}^0{K}_{\textrm{S}}^0$ mode is measured to be ${\mathcal{A}}^{CP}\left({D}^0\to {K}_{\textrm{S}}^0{K}_{\textrm{S}}^0\right)=\left(1.86\pm 1.04\pm 0.41\right)\%,$ A CP D 0 → K S 0 K S 0 = 1.86 ± 1.04 ± 0.41 % , where the first uncertainty is statistical, and the second is systematic. This measurement represents the most precise single-experiment determination of this quantity to date.