Quantum detection of CP violation in the $t\bar{t}$ system: production

Abstract:We investigate how possible new CP-violating top-quark interactions are encoded in the quantum state of a produced $t\bar t$ pair. We derive analytic expressions for the production density matrix in several benchmark channels relevant to hadron, lepton and photon colliders. In a common spin basis, we identify two characteristic CP-odd structures in the Fano--Bloch decomposition: a difference between the top and antitop polarisation vectors and an antisymmetric component of the spin-correlation matrix. We construct observables that directly probe these structures and study how quantum information measures, including discord, concurrence, magic and trace distance, respond to CP-even and CP-odd SMEFT contributions. Finally, using current measurements and future collider projections, we assess the sensitivity of these observables to possible new sources of CP violation in top-quark production. This establishes the production-level framework whose experimental reconstruction is developed in a companion paper.

arXiv:2607.25029 [hep-ph]

(or arXiv:2607.25029v1 [hep-ph] for this version)

https://doi.org/10.48550/arXiv.2607.25029 arXiv-issued DOI via DataCite (pending registration)