Improved tests of entanglement and Bell inequalities with LHC tops

Abstract

We discuss quantum entanglement in top pair production at the LHC. Near the $t\bar{t}$ threshold, entanglement observables are enhanced by suppressing the contribution of $q\bar{q}$ subprocesses, which is achieved by a simple cut on the velocity of the $t\bar{t}$ system in the laboratory frame. Furthermore, we design new observables that directly measure the relevant combinations of $t\bar{t}$ spin correlation coefficients involved in the measurement of entanglement and Bell inequalities. As a result, the statistical sensitivity is enhanced, up to a factor of 7 for Bell inequalities near threshold.

Comments: LaTeX 21 pages. Final version in EPJC