First Evidence for Mixing-Induced (Formula presented) Violation in (Formula presented) Decays in (Formula presented) Collisions at (Formula presented)

A novel machine-learning-based flavor-tagging algorithm combining same-side and opposite-side tagging is used to obtain the equivalent of 27 500 tagged (Formula presented) decays from (Formula presented) collisions at (Formula presented), collected by the CMS experiment and corresponding to an integrated luminosity of (Formula presented). A time- and flavor-dependent angular analysis of the (Formula presented) final state, consistent with a (Formula presented) decay, is used to measure parameters of the (Formula presented) system. The weak phase is measured to be (Formula presented), which, combined with the (Formula presented) CMS result, gives (Formula presented). This value differs from zero by 3.2 standard deviations, providing the first evidence for mixing-induced (Formula presented) violation in (Formula presented) decays. All measured physics parameters are found to agree with standard model predictions where available.