Measurement of W-boson helicity fractions in top-quark decays using cos theta
Fully 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 cou...
| Autores: | , , , , , , , , , , , , |
|---|---|
| Tipo de recurso: | artículo |
| Fecha de publicación: | 2009 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/22343 |
| Acceso en línea: | http://hdl.handle.net/10261/22343 |
| Access Level: | acceso abierto |
| Palabra clave: | Helicity W boson Top quark |
| Sumario: | Fully 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. |
|---|