Decoherence effects for Quantum Observables at collider

Lately, it has been spreading a fast-growing interest in the many applications of typical Quantum Information concepts across all energy scales. At the same time, it is reasonable to wonder whether purely QM effects can be probed at LHC scales and if so, to what extent this can be done. A recent work addressing this problem was proposed in 2020 by Afik and de Nova, and only in 2023 (ATLAS) and 2024 (CMS) experiments provided the first observation of spin quantum entanglement in top pair production. Since then, the interest in this subject has increased. The underlying principle is the use of observables borrowed from Quantum Information, e.g. entanglement and Bell inequalities, to study the properties of fundamental interactions as well as providing a new direction to look for new physics. All the studies so far published consider entangled particles as closed systems, which, however, are rather uncommon. Throughout this work, we will focus on entangled ttbar pairs, produced by the decay of an off-shell Higgs boson, regarding them as open systems able to exchange particles with the environment. As a result, we can study how the emission affects entanglement, a process known as decoherence, as well as what consequences it has on the predictions provided by the Quantum Observables.