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Título

Measurement of W-boson helicity fractions in top-quark decays using cos theta

AutorCDF Collaboration; Cabrera, Susana ; Cuenca Almenar, Cristóbal ; Álvarez González, B.; Casal, Bruno ; Cuevas, Javier ; Gómez, G. ; Rodrigo, Teresa ; Ruiz Jimeno, Alberto ; Scodellaro, Luca ; Vila, Iván ; Vilar, Rocío ; Aaltonen, T.
Palabras claveHelicity
W boson
Top quark
Fecha de publicación20-abr-2009
EditorElsevier
CitaciónPhysics Letters - Section B 674 (3): 160-167 (2009)
ResumenFully reconstructed a t (t) over bar -> W(+)bW(-)(b) over bar -> l nu q (q) over bar 'b (b) over bar events are used to determine the fractions of right-handed (f(+)) and longitudinally polarized (f(0)) 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 pp 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 f(0) = 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 f(0) fixed to the theoretically expected value of 0.70. Model-independent fits are also performed and simultaneously determine f(0) =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.
Versión del editorhttp://dx.doi.org/ 10.1016/j.physletb.2009.02.040
URIhttp://hdl.handle.net/10261/22343
DOI10.1016/j.physletb.2009.02.040
ISSN0370-2693
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