Post-decay quantum entanglement in top pair production

TL;DR

This paper investigates quantum entanglement in top quark pair production at the LHC, demonstrating that entanglement persists through decay and can be experimentally tested with current and future data.

Contribution

It reveals the presence of spin entanglement between top quarks and their decay products, and proposes methods to verify this entanglement experimentally.

Findings

Entanglement persists between decay products in certain kinematic regions.

High statistical significance for entanglement detection at LHC Run 2 and Run 3.

Proposes experimental tests for fermion-boson and boson-boson entanglement in top pair events.

Abstract

Top pairs produced at the Large Hadron Collider exhibit quantum entanglement of their spins near threshold and for boosted, central $t \bar t$ pairs. The entanglement is maintained between the decay products, in particular between the top quark and the $W^-$ boson from the anti-quark (or vice-versa, between $\bar t$ and $W^+$) in certain kinematical regions. Therefore, $t \bar t$ production provides a rare opportunity to verify the spin entanglement between a fermion and a boson. The $tW$ entanglement can be probed at the $7\sigma$ level near threshold with Run 2 data, and at the $5\sigma$ level in the boosted region with the foreseen Run 3 luminosity. In addition, the entanglement between the two $W$ bosons can be probed at the $4\sigma$ level at the LHC Run 3.