Regular Article - Theoretical Physics
Observing spin correlations at the LHC
School of Physics and Astronomy, University of Glasgow, G12 8QQ, Glasgow, UK
Accepted: 28 August 2021
Published online: 13 September 2021
Spin correlations in the production of top-antitop quark () pairs at the Large Hadron Collider (LHC) are an experimentally verified prediction of the Standard Model. In this paper, we compute the full spin density matrix for production at next-to-leading order precision in QCD, for center-of-mass energies of 13 and 14 . We find that the additional emission of a Z boson leads to significantly different spin correlations with respect to the case, and induces small longitudinal polarisations of the top quarks. We further propose an analysis strategy that could lead to the observation of spin correlations in events at the end of Run 3 of the LHC, or possibly earlier by combining the ATLAS and CMS datasets. In addition, we show that the pure angular information contained in the spin density matrix provides novel constraints on the dimension-6 effective field theory operators relevant to the t-Z interaction, without any reference to the total production rates.
© The Author(s) 2021
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