The double differential distribution in polar angles, ${{\mathit \theta}_{{1}}}$ (${{\mathit \theta}_{{2}}}$) of the decay particle of the top (anti-top) decay products, is parametrized as (1/${{\mathit \sigma}}$)d${{\mathit \sigma}}$/(dcos ${{\mathit \theta}_{{1}}}$ dcos ${{\mathit \theta}_{{2}}}$) = (1/4) ( 1 + A$_{t}$ cos ${{\mathit \theta}_{{1}}}$ + A$_{{{\overline{\mathit t}}}}$ cos ${{\mathit \theta}_{{2}}}$ $−$ C cos ${{\mathit \theta}_{{1}}}$ cos ${{\mathit \theta}_{{2}}}$ ). The charged lepton is used to tag ${{\mathit t}}$ or ${{\overline{\mathit t}}}$. The coefficient A$_{t}$ and A$_{{{\overline{\mathit t}}}}$ measure the average helicity of ${{\mathit t}}$ and ${{\overline{\mathit t}}}$, respectively. A$_{CPC}$ = A$_{t}$ = A$_{{{\overline{\mathit t}}}}$ assumes $\mathit CP$ conservation, whereas A$_{CPV}$ = A$_{t}$ = $−A_{{{\overline{\mathit t}}}}$ corresponds to maximal $\mathit CP$ violation.

VALUE DOCUMENT ID TECN  COMMENT • • We do not use the following data for averages, fits, limits, etc. • • $-0.035$ $\pm0.014$ $\pm0.037$ 1 AAD 2013 BE ATLS A$_{CPC}$ $0.020$ $\pm0.016$ ${}^{+0.013}_{-0.017}$ 1 AAD 2013 BE ATLS A$_{CPV}$ 1  Based on 4.7 fb${}^{-1}$ of data using the final states containing one or two isolated electrons or muons and jets with at least one ${{\mathit b}}$-tag.

References:

AAD 2013BE PRL 111 232002 Measurement of Top Quark Polarization in Top-Antitop Events from Proton$−$Proton Collisions at $\sqrt {s }$ = 7 TeV using the ATLAS Detector