Speaker
Description
Collider proposals for Bell tests with unstable particles (e.g., $H \to ZZ^{\ast},\; WW^{\ast}$) face two structural issues: measurement settings are not freely choosable, and the boson-pair spin density matrix is inferred indirectly from decay kinematics through QFT-based reconstruction, obscuring the operational meaning of the Bell observables and introducing theory dependence in the inference. Motivated by recent critical discussions of these limitations, we develop an open-quantum-systems formulation in which the reduced spin description is lifted to an enlarged parent–daughter framework including both the parent spin degrees of freedom and experimentally accessible decay-product degrees of freedom. Using a Lindblad dilation perspective (in correspondence with the Wigner–Weisskopf approach to decay), the total dynamics is formulated as a completely positive, trace-preserving evolution on the enlarged Hilbert space, enabling Bell-type correlators to be defined directly in terms of measured final-state degrees of freedom. We discuss how the framework interfaces with standard collider angular analyses and delineate the scope and limitations of Bell-type claims in the LHC setting.