Parameter inference from final-state entanglement in Higgs boson decays

The decay out states of unstable Standard Model (SM) particles provide a natural, well-defined quantum-information probe of the SM parameter space. We use Higgs boson decays as a test case: After tracing out kinematics, we compute entanglement among final-state spins and colors across all decay channels and investigate a near-maximal entanglement-entropy criterion. This criterion turns out to be informative about fundamental parameters. Within the SM, we find that the entanglement entropy exhibits a global maximum close to the observed Higgs boson mass and the measured W mass, the latter being equivalent to the S U ( 2 ) L gauge coupling. In a two-parameter kappa framework, applying the same criterion is consistent with an SM-like balance between Higgs boson couplings to vector bosons and to fermions, providing sensitivity to the ratio of the sector-wide rescalings. These results suggest that entanglement extremality may serve as a complementary handle on fundamental parameters.