Research Papers in Physics and Astronomy


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Published by American Physical Society. Phys. Rev. Lett. 84, 216 (2000). Copyright © 2000 American Physical Society. Permission to use.


We use the transverse momentum spectrum of leptons in the decay chain tbW with W 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.

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