Quantum SMEFT tomography: top quark pair production at the LHC

Abstract

Quantum information observables, such as entanglement measures, provide a powerful way to characterize the properties of quantum states. We propose to use them to probe the structure of fundamental interactions and to search for new physics at high energy. Inspired by recent proposals to measure entanglement of top quark pairs produced at the LHC, we examine how higher-dimensional operators in the framework of the SMEFT modify the Standard Model expectations. We explore two regions of interest in the phase space where the Standard Model produces maximally entangled states: at threshold and in the high-energy limit. We unveil a non-trivial pattern of effects, which depend on the initial state partons, q q or gg, on whether only linear or up to quadratic SMEFT contributions are included, and on the phase space region. In general, we find that higher-dimensional effects lower the entanglement predicted in the Standard Model.

Improved tests of entanglement and Bell inequalities with LHC tops

“…This goal has been recently addressed in several interesting works [6][7][8][9][10], dealing with the top-antitop system (t t) at the Large Hadron Collider (LHC). As stressed in Ref.…”

“…In Refs. [6][7][8][9][10], certain sufficient conditions for entanglement and CHSH violation were obtained, together with a phenomenological exploration of their testability. In Ref.…”

SMEFT predictions for gg → hh at full NLO QCD and truncation uncertainties

“…Furthermore, at amplitude squared level, there are several possibilities to truncate the expansion in the canonical dimension, related to the inclusion of squared dimension six terms and double operator insertions. The discussion of truncation uncertainties recently gained considerable attention in the literature [14][15][16][17][18][19][20][21][22], showing that the uncertainties have to be assessed on a case-by-case basis.…”

Constraining new physics in entangled two-qubit systems: top-quark, tau-lepton and photon pairs

“…A first study of the impact of effective operators of dimension six -within the SM Effective Field Theory (SMEFT) -has been presented in [25] for the entanglement of the spins of top-quark pairs. In this work we want to provide a comprehensive discussion for the case of bipartite, two-qubit like systems available at colliders and explore to what extent entanglement can provide a new tool in the search of physics beyond the SM.…”