We calculate, for the first time, the next-to-next-to-leading order (NNLO) QCD corrections to spin correlations in top quark pair production at the LHC. The NNLO corrections play an important role in the description of the corresponding differential distributions. We observe that the standard model calculation describes the available $\mathrm{\Delta }{\varphi }_{\ell \ell }$ data in the fiducial region but does not agree with the $\mathrm{\Delta }{\varphi }_{\ell \ell }$ measurement extrapolated to full phase space. Most likely this discrepancy is due to the difference in precision between existing event generators and NNLO calculations for dilepton top-pair final states.

• Received 5 February 2019

DOI:https://doi.org/10.1103/PhysRevLett.123.082001

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Published by the American Physical Society