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Legacy ttZ measurement published in JHEP

ttZ event display

Our comprehensive Run 2 measurement of \(t\bar{t}Z\) production has been published in JHEP. This analysis represents the state-of-the-art in \(t\bar{t}Z\) physics at the LHC.

Using the full 140 fb\(^{-1}\) dataset collected by ATLAS during LHC Run 2 (2015–2018), we measured:

\[\sigma_{t\bar{t}Z} = 0.86 \pm 0.04\,(\text{stat.}) \pm 0.04\,(\text{syst.})\,\text{pb}\]

in agreement with the Standard Model prediction.

Three results in one paper

This analysis is notable for combining three distinct physics results:

  1. Differential cross sections — the most precise unfolded distributions of the \(t\bar{t}Z\) system, at both particle and parton level.
  2. EFT interpretation — limits on a large number of dimension-6 SMEFT operators involving the top quark, using the differential distributions.
  3. Spin correlations — the first measurement of spin correlations in \(t\bar{t}Z\), disfavouring the no-correlation hypothesis at 1.8σ.

Links: arXiv:2312.04450 · HEPData · ATLAS