Speaker
Description
Polarisation and spin correlations in diboson systems are powerful probes for precision tests of the Standard Model and searches for new physics. More recently, viewing these observables through the lens of quantum information, such as assessing whether diboson systems exhibit quantum entanglement, has opened a compelling new frontier in these investigations. They also provide a unique opportunity to test quantum information principles at the highest accessible energy scales. We analyze the angular coefficients for the $pp \to ZZ \to 4 \ell$ and Higgs decay to di-bosons $h \to WW$ and $h \to WW$, incorporating higher-order QCD and electroweak corrections. For Higgs decays, we consider both fully leptonic and semileptonic final states. Guided by the fundamental properties of the spin density matrix, we assess the stability of the two-qutrit interpretation under radiative effects. For the $pp \to ZZ \to 4 \ell$ process, NLO QCD corrections preserve the two-qutrit structure but weaken entanglement indicators, an effect that can be partially mitigated by jet binning. In contrast, EW introduce non-factorizable contributions that modify the quantum properties of the system. While these effects can be largely depleted by selecting events with a double-resonant $ZZ$ structure, such a kinematic handle is not available for Higgs decays. For $h \to ZZ$, channel, singly-resonant NLO electroweak corrections substantially distort the angular coefficients, challenging the description of these events as a two-qutrit system. These effects are milder for $h \to WW$ compared with $h \to ZZ$. For both processes, semileptonic final states exhibit greater stability than fully leptonic final states.