Measurement of the Helicity of W Bosons in Top Quark Decays

Authors

• T. Affolder, Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California
• Kenneth A. Bloom, University of Nebraska-LincolnFollow
• Collider Detector at Fermilab Collaboration

Document Type

Article

Date of this Version

1-10-2000

Comments

Published by American Physical Society. Phys. Rev. Lett. 84, 216 (2000). http://prl.aps.org. Copyright © 2000 American Physical Society. Permission to use.

Abstract

We use the transverse momentum spectrum of leptons in the decay chain t → bW with W → lν to measure the helicity of the W bosons in the top quark rest frame. Our measurement uses a tt̅ sample isolated in 106 ± 4 pb^-1 of data collected in pp̅ collisions at √s = 1.8 TeV with the CDF detector at the Fermilab Tevatron. Assuming a standard V-A weak decay, we find that the fraction of W’s with zero helicity in the top rest frame is F₀ = 0.91 ± 0.37(stat)± 0.13(syst), consistent with the standard model prediction of F₀= 0.70 for a top mass of 175 GeV/c².