We present a measurement of the fractions F(0) and F(+) of longitudinally polarized and right-handed W bosons in top-quark decays using data collected with the CDF II detector. The data set used in the analysis corresponds to an integrated luminosity of approximately 318 pb(-1). We select t (t) over bar candidate events with one lepton, at least four jets, and missing transverse energy. Our helicity measurement uses the decay angle theta(*), which is defined as the angle between the momentum of the charged lepton in the W boson rest frame and the W momentum in the top-quark rest frame. The cos theta(*) distribution in the data is determined by full kinematic reconstruction of the t (t) over bar candidates. We find F(0)=0.85(-0.22)(+0.15)(stat)+/- 0.06(syst) and F(+)=0.05(-0.05)(+0.11)(stat)+/- 0.03(syst), which is consistent with the standard model prediction. We set an upper limit on the fraction of right-handed W bosons of F(+)< 0.26 at the 95% confidence level. RI Ruiz, Alberto/E-4473-2011; Robson, Aidan/G-1087-2011; De Cecco, Sandro/B-1016-2012; Prokoshin, Fedor/E-2795-2012; Azzi, Patrizia/H-5404-2012

Measurement of the helicity fractions of W bosons from top quark decays using fully reconstructed t(t)over-bar events with CDF II

PIACENTINO, Giovanni Maria;
2007

Abstract

We present a measurement of the fractions F(0) and F(+) of longitudinally polarized and right-handed W bosons in top-quark decays using data collected with the CDF II detector. The data set used in the analysis corresponds to an integrated luminosity of approximately 318 pb(-1). We select t (t) over bar candidate events with one lepton, at least four jets, and missing transverse energy. Our helicity measurement uses the decay angle theta(*), which is defined as the angle between the momentum of the charged lepton in the W boson rest frame and the W momentum in the top-quark rest frame. The cos theta(*) distribution in the data is determined by full kinematic reconstruction of the t (t) over bar candidates. We find F(0)=0.85(-0.22)(+0.15)(stat)+/- 0.06(syst) and F(+)=0.05(-0.05)(+0.11)(stat)+/- 0.03(syst), which is consistent with the standard model prediction. We set an upper limit on the fraction of right-handed W bosons of F(+)< 0.26 at the 95% confidence level. RI Ruiz, Alberto/E-4473-2011; Robson, Aidan/G-1087-2011; De Cecco, Sandro/B-1016-2012; Prokoshin, Fedor/E-2795-2012; Azzi, Patrizia/H-5404-2012
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11695/1697
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