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

A bstract A measurement of CP asymmetry in $$ {D}^0\to {K}_{\textrm{S}}^0{K}_{\textrm{S}}^0 $$ D 0 → K S 0 K 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 $$ {D}^0\to {K}_{\textrm{S}}^0{\pi}^{+}{\pi}^{-} $$ D 0 → K S 0 π + π − decay is used as calibration channel to cancel residual detection and production asymmetries. The time-integrated CP asymmetry for the $$ {D}^0\to {K}_{\textrm{S}}^0{K}_{\textrm{S}}^0 $$ D 0 → K S 0 K 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.