[工程科技]ATLAS sensitivity to top quark and W boson polarization in tbar{t} events.pdf

ATLAS sensitivity to top quark ¯ and W boson polarization in tt events 5 0 0 2 g F. Hubaut, E. Monnier, P. Pralavorio u A Centre de Physique des Particules de Marseille, CNRS/IN2P3 - Univ. M´editerran´ee, Marseille - France 1 3 K. Smolek 1 v Institute of Experimental and Applied Physics, Czech Technical University, 1 6 Prague - Czech Republic 0 8 V. Simak 0 5 Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, and 0 / Institute of Physics of the Czech Academy of Sciences, Prague - Czech Republic x e - p e h : v i X r Abstract a Stringent tests on top quark production and decay mechanisms are provided by the measure- ment of the top quark and W boson polarization. This paper presents a detailed study of these two measurements with the ATLAS detector, in the semileptonic (tt → WWbb → lνj 1j 2bb) ¯ and dileptonic (tt → WWbb → lνlνbb) tt channels. It is based on leading-order Monte Carlo generators and on a fast simulation of the detector. A particular attention is paid to the system- atic uncertainties, which dominate the statistical errors after one LHC year at low luminosity (10 fb−1), and to the background estimate. Combining results from both channel studies, the longitudinal component of the W polarization (F ) can be measured with a 2% accuracy and the