Search for right-handed W bosons in top quark decay

TL;DR

This paper measures the fraction of right-handed W bosons in top quark decays using data from the Fermilab Tevatron, finding results consistent with the Standard Model prediction.

Contribution

First measurement of the right-handed W boson fraction in top decays using kinematic reconstruction and angular analysis at the Tevatron.

Findings

Measured f+ = 0.00 ± 0.13 (stat) ± 0.07 (syst)

Results are consistent with the Standard Model prediction of near zero

Used 230 pb^-1 of data from the DO detector at Fermilab

Abstract

We present a measurement of the fraction f+ of right-handed W bosons produced in top quark decays, based on a candidate sample of $t\bar{t}$ events in the lepton+jets decay mode. These data correspond to an integrated luminosity of 230pb^-1, collected by the DO detector at the Fermilab Tevatron $p\bar{p}$ Collider at sqrt(s)=1.96 TeV. We use a constrained fit to reconstruct the kinematics of the $t\bar{t}$ and decay products, which allows for the measurement of the leptonic decay angle $\theta^*$ for each event. By comparing the $\cos\theta^*$ distribution from the data with those for the expected background and signal for various values of f+, we find f+=0.00+-0.13(stat)+-0.07(syst). This measurement is consistent with the standard model prediction of f+=3.6x10^-4.