## 摘要

The combination of measurements of the W boson polarization in top quark decays performed by the ATLAS and CMS collaborations is presented. The measurements are based on proton-proton collision data produced at the LHC at a centre-of-mass energy of 8 TeV, and corresponding to an integrated luminosity of about 20 fb^{−1} for each experiment. The measurements used events containing one lepton and having different jet multiplicities in the final state. The results are quoted as fractions of W bosons with longitudinal (F_{0}), left-handed (F_{L}), or right-handed (F_{R}) polarizations. The resulting combined measurements of the polarization fractions are F_{0} = 0.693 ± 0.014 and F_{L} = 0.315 ± 0.011. The fraction F_{R} is calculated from the unitarity constraint to be F_{R} = −0.008 ± 0.007. These results are in agreement with the standard model predictions at next-to-next-to-leading order in perturbative quantum chromodynamics and represent an improvement in precision of 25 (29)% for F_{0} (F_{L}) with respect to the most precise single measurement. A limit on anomalous right-handed vector (V_{R}), and left- and right-handed tensor (g_{L}, g_{R}) tWb couplings is set while fixing all others to their standard model values. The allowed regions are [−0.11, 0.16] for V_{R}, [−0.08, 0.05] for g_{L}, and [−0.04, 0.02] for g_{R}, at 95% confidence level. Limits on the corresponding Wilson coefficients are also derived. [Figure not available: see fulltext.]

原文 | ???core.languages.en_GB??? |
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文章編號 | 51 |

期刊 | Journal of High Energy Physics |

卷 | 2020 |

發行號 | 8 |

DOIs | |

出版狀態 | 已出版 - 1 8月 2020 |