Improved tests of entanglement and Bell inequalities with LHC tops

Abstract

Abstract We discuss quantum entanglement in top pair production at the LHC. Near the $$t {\bar{t}}$$ t t ¯ threshold, entanglement observables are enhanced by suppressing the contribution of $$q {\bar{q}}$$ q q ¯ subprocesses, which is achieved by a simple cut on the velocity of the $$t {\bar{t}}$$ t t ¯ system in the laboratory frame. Furthermore, we design new observables that directly measure the relevant combinations of $$t{\bar{t}}$$ t 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.