Measurement of W-Boson Polarization in Top-quark Decay using the Full CDF Run II Data Set

TL;DR

This paper measures the polarization states of W bosons from top-quark decays using the full CDF Run II dataset, providing results consistent with the Standard Model predictions.

Contribution

It presents a model-independent measurement of W boson polarization fractions in top-quark decays using the complete CDF Run II data set.

Findings

Measured f_0 = 0.726 +/- 0.066 (stat) +/- 0.067 (syst)

Measured f_+ = -0.045 +/- 0.044 (stat) +/- 0.058 (syst)

Results are consistent with Standard Model expectations.

Abstract

We measure the polarization of W bosons from top-quark (t) decays into final states with a charged lepton and jets, tt --> WbWb --> lvbqqb, using the full Run II data set collected by the CDF II detector. A model-independent method simultaneously determines the fraction of longitudinal (f_0) and right-handed (f_+) W bosons to yield f_0 = 0.726 +/- 0.066 (stat) +/- 0.067 (syst) and f_+ = -0.045 +/- 0.044 (stat) +/- 0.058 (syst) with a correlation coefficient of -0.69. Additional results are presented under various standard model assumptions. No significant discrepencies with the standard model are observed.