CDF Logo CDF W boson helicity fractions measurement in tt dilepton channel
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Abstract

We present the measurements of the fraction of longitudinally (f0) and right-handed (f+) polarized W bosons from top quark decay using tt events with the dilepton final state. W boson helicity fractions are determined by a comparison of angular distribution of leptons in W rest-frame (cos θ*) with the templates corresponding to left-handed, right-handed an longitudinal fractions exclusively. Using CDF Run II data corresponding to integrated luminosity of 4.8 fb-1, three measurements are performed. A model independent simultaneous measurement of f0 and f+ yields

f0 = 0.78 +0.19-0.20 (stat.) +- 0.06 (syst.)
f+ = -0.12 +0.11-0.10 (stat.) +- 0.04 (syst.)

A measurement of f0 constraining f+ to its Standard Model value of 0.0 yields

f0 = 0.62 +- 0.11 (stat.) +- 0.06 (syst.)

while a measurement of f+ constraining f0 to its Standard Model value of 0.70 gives

f+ = -0.07 + 0.06- 0.05 (stat.) +- 0.03 (syst.)

All the results are consistent with Standard Model expectations.

 

Supporting documents

  • More details are provided in the CDF public note (ps pdf)

     

  • General remarks

  • The preliminary results were blessed in the CDF Top group on Nov 18, 2010.
  • Please contact us if you have any questions about including these results in a presentation.

     

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     Updated by Roman Lysak
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    Last modified: Tue Jan 18 16:29:35 CET 2011