Combination of CDF and D0 measurements of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>W</mml:mi></mml:math>boson helicity in top quark decays

We report the combination of recent measurements of the helicity of the $W$ boson from top quark decay by the CDF and D0 collaborations, based on data samples corresponding to integrated luminosities of $2.7--5.4\text{ }\text{ }\mathrm{f}{\mathrm{b}}^{\ensuremath{-}1}$ of $p\overline{p}$ collisions collected during Run II of the Fermilab Tevatron collider. Combining measurements that simultaneously determine the fractions of $W$ bosons with longitudinal (${f}_{0}$) and right-handed (${f}_{+}$) helicities, we find ${f}_{0}=0.722\ifmmode\pm\else\textpm\fi{}0.081[\ifmmode\pm\else\textpm\fi{}0.062(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.052(\mathrm{syst})]$ and ${f}_{+}=\ensuremath{-}0.033\ifmmode\pm\else\textpm\fi{}0.046[\ifmmode\pm\else\textpm\fi{}0.034(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.031(\mathrm{syst})]$. Combining measurements where one of the helicity fractions is fixed to the value expected in the standard model, we find ${f}_{0}=0.682\ifmmode\pm\else\textpm\fi{}0.057[\ifmmode\pm\else\textpm\fi{}0.035(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.046(\mathrm{syst})]$ for fixed ${f}_{+}$ and ${f}_{+}=\ensuremath{-}0.015\ifmmode\pm\else\textpm\fi{}0.035[\ifmmode\pm\else\textpm\fi{}0.018(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.030(\mathrm{syst})]$ for fixed ${f}_{0}$. The results are consistent with standard model expectations.

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