Bell Inequalities and Quantum Correlations in $H\to ZZ\to 2e2\mu$

We investigate quantum correlations in Higgs-boson decays $(H\to Z{Z}^{\ast }\to 2e2\mu )$ using CMS open data at $\sqrt{s}$ = 8 TeV, incorporating realistic detector effects. By reconstructing the polarization density matrix of the two-boson system and evaluating the Collins-Gisin-Linden-Massar-Popescu (CGLMP) Bell operator $I_3$, we quantify entanglement in the $ZZ$ state. Our analysis yields an $I_3$ value of $2.152\pm 0.003$ for signal events $(H\to Z{Z}^{\ast })$, indicating the presence of quantum entanglement. The non-resonant continuum background events $(pp\to ZZ)$ yield $I_3=1.158\pm 0.012$, suggesting the absence of quantum correlations. These results demonstrate the feasibility of testing fundamental quantum mechanics at high energy colliders.