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Search for CP violation in ${\text{D}}^{0}\to {\text{K}}_{\text{S}}^{0}{\text{K}}_{\text{S}}^{0}$ decays in proton–proton collisions at $\sqrt{s}=13\phantom{\rule{0.166667em}{0ex}}\text{Te}\phantom{\rule{-0.80002pt}{0ex}}\text{V}$

2024    CERN İşbirliği

A search is reported for charge-parity $\mathrm{CP}$ violation in ${\text{D}}^{0}\to {\text{K}}_{\text{S}}^{0}{\text{K}}_{\text{S}}^{0}$ decays, using data collected in proton–proton collisions at $\sqrt{s}=13\phantom{\rule{0.166667em}{0ex}}\text{Te}\phantom{\rule{-0.80002pt}{0ex}}\text{V}$ recorded by the CMS experiment in 2018. The analysis uses a dedicated data set that corresponds to an integrated luminosity of 41.6 $\phantom{\rule{0.166667em}{0ex}}{\text{fb}}^{-1}$ , which consists of about 10 billion events containing a pair of b hadrons, nearly all of which decay to charm hadrons. The flavor of the neutral D meson is determined by the pion charge in the reconstructed decays $\text{D}_{}^{\ast +}\to {\text{D}}^{0}{\pi }^{+}$ and $\text{D}_{}^{\ast -}\to {\overline{\text{D}}}^{0}{\pi }^{-}$ . The $\mathrm{CP}$ asymmetry in ${\text{D}}^{0}\to {\text{K}}_{\text{S}}^{0}{\text{K}}_{\text{S}}^{0}$ is measured to be ${A}_{\mathrm{CP}}\left({\text{K}}_{\text{S}}^{0}{\text{K}}_{\text{S}}^{0}\right)=\left(6.2±3.0±0.2±0.8\right)%$ , where the three uncertainties represent the statistical uncertainty, the systematic uncertainty, and the uncertainty in the measurement of the $\mathrm{CP}$ asymmetry in the ${\text{D}}^{0}\to {\text{K}}_{\text{S}}^{0}{\pi }^{+}{\pi }^{-}$ decay. This is the first $\mathrm{CP}$ asymmetry measurement by CMS in the charm sector as well as the first to utilize a fully hadronic final state.