Measurement of W-boson helicity fractions in top-quark decays using cos Academic Article uri icon


  • Fully reconstructed t over(t, ) W+ b W- over(b, ) q over(q, ) b over(b, ) events are used to determine the fractions of right-handed (f+) and longitudinally polarized (f0) W bosons produced in top-quark decays. The helicity fractions are sensitive to the couplings and the Dirac structure of the Wtb vertex. This Letter reports measurements of the W-boson helicity fractions from two different methods using data corresponding to an integrated luminosity of 1.9 fb- 1 of p over(p, ) collisions at a center-of-mass energy of 1.96 TeV collected by the CDF II detector operating at the Fermilab Tevatron. Combining the results from the two methods, we find f0 = 0.62 0.10 (stat) 0.05 (syst) under the assumption that f+ = 0, and f+ = - 0.04 0.04 (stat) 0.03 (syst) with f0 fixed to the theoretically expected value of 0.70. Model-independent fits are also performed and simultaneously determine f0 = 0.66 0.16 (stat) 0.05 (syst) and f+ = - 0.03 0.06 (stat) 0.03 (syst). All these results are consistent with standard model expectations. 2009 Elsevier B.V.

published proceedings

  • Physics Letters B

author list (cited authors)

  • Aaltonen, T., Adelman, J., Akimoto, T., lvarez Gonzlez, B., Amerio, S., Amidei, D., ... Zucchelli, S.

publication date

  • January 1, 2009 11:11 AM