Speaker
Description
Partonic spin correlations in Higgs boson decays provide a novel opportunity to probe the CP structure of the Higgs--gluon coupling at future lepton colliders. Translating this physics potential into a realistic measurement requires the identification of different gluon splitting modes, whose contributions can otherwise largely cancel in inclusive observables. In this work, we take a step towards a detector-level measurement using full-simulation samples of the CEPC AGORA detector at $\sqrt{s}=240~\mathrm{GeV}$. Building on the jet-tagging framework developed for the AGORA detector studies, we develop an extended seven-class jet tagger capable of distinguishing quark flavors and different gluon splitting modes. This enables the separation of $H\to gg$ events into $gggg$, $ggq\bar{q}$, and $q\bar{q}q\bar{q}$ topologies, providing the experimental basis for measuring their event rates and spin-sensitive observables. The study establishes a pathway towards detector-level measurements of gluon spin correlations and, ultimately, direct constraints on the CP structure of the Higgs--gluon coupling at the CEPC.