Probing Higgs CP properties at the CEPC in the $$e^{+} e^{-} \rightarrow Z H \rightarrow l^{+} l^{-}H$$ e + e - → Z H → l + l - H using optimal variables

Abstract

Abstract In the Circular Electron Positron Collider (CEPC), a measurement of the Higgs CP mixing through $$e^{+} e^{-} \rightarrow Z H \rightarrow l^{+} l^{-}(e^{+} e^{-} /\mu ^{+} \mu ^{-}) H(\rightarrow b \bar{b} / c \bar{c} / g g)$$ e + e - → Z H → l + l - ( e + e - / μ + μ - ) H ( → b b ¯ / c c ¯ / g g ) process is presented, with $$5.6\ \text{ ab}^{-1}$$ 5.6 ab - 1 $$e^{+} e^{-}$$ e + e - collision data at the center-of-mass energy of $$240\ \textrm{GeV}$$ 240 GeV . In this study, the CP-violating parameter $$\tilde{c}_{Z \gamma }$$ c ~ Z γ is constrained between the region of $$ -0.30$$ - 0.30 and 0.27 and $$\tilde{c}_{Z Z}$$ c ~ ZZ between $$-0.06$$ - 0.06 and 0.06 at $$68\%$$ 68 % confidence level. This study demonstrates the great potential of probing Higgs CP properties at the CEPC.