Top W helicity measurement (lepton pT method)

A Measurement of the Fraction of Longitudinally-Polarized W Bosons Produced in Top-Quark Decays Using Charged-Lepton p_Tat CDF II

N. Goldschmidt, K. Bloom, S. Miller, D. Gerdes, D. Amidei

Table of Contents

Abstract


	We measure the fraction of longitudinally-polarized W bosons produced in top-quark decays by analyzing the charged-lepton p_T spectrum of tt candidate events. We find that the fraction of W bosons with longitudinal polarization is F₀ = 0.88 +0.12 -0.47 (stat.+syst.), F₀ > 0.24 @ 95% CL in the lepton plus jets displaced secondary vertex tagged sample, F₀ < 0.52 @ 95% CL in the dilepton sample, and F₀ = 0.27 +0.35 -0.24 (stat.+syst), F₀ < 0.88 @ 95% CL in the combined analysis.

A note describing this analysis can be found here.

Public Presentations

Plots



		The lepton+jets charged-lepton p_T data plotted against the Standard Model signal and background models. The tt contribution is normalized to the measured cross section xx. PDF version

		The lepton+jets charged-lepton p_T data plotted against the best fit. The inset plot shows the likelihood projected along the F₀ axis. PDF version

		Feldman-Cousins confidence belts for the lepton+jets only measurement. The heavy line indicates the Maximum Likelihood Estimate, \hat{F}_0 = 0.88. PDF version

		The dilepton charged-lepton p_T data plotted against the Standard Model signal and background models. The tt contribution is normalized to the measured cross section xx. PDF version

		The dilepton charged-lepton p_T data plotted against the best fit. The inset plot shows the likelihood projected along the F₀ axis. PDF version

		Feldman-Cousins confidence belts for the dilepton only measurement. The heavy line indicates the Maximum Likelihood Estimate, \hat{F}_0 = -0.54. PDF version

		The combined lepton+jets and dilepton charged-lepton p_T data plotted against the best fit. The inset plot shows the likelihood projected along the F₀ axis. PDF version

		Feldman-Cousins confidence belts for the combined lepton+jets and dilepton measurement. The heavy line indicates the Maximum Likelihood Estimate, \hat{F}_0 = 0.27. PDF version