Search for right-handed W bosons in top quark decay

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 tt-bar events in the lepton+jets decay mode. These data correspond to an integrated luminosity of 230 pb(−1), collected by the D0 detector at the Fermilab Tevatron pp-bar Collider at s√=1.96 TeV. We use a constrained fit to reconstruct the kinematics of the tt-bar and decay products, which allows for the measurement of the leptonic decay angle θ∗ for each event. By comparing the cosθ∗ 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(+)=3.6×10(−4).