@Article{Aguilar-Saavedra+Bernabeu2010,
author="Aguilar-Saavedra, J. A.
and Bernabeu, J.",
title="W polarisation beyond helicity fractions in top quark decays",
journal="Nuclear Physics B",
year="2010",
publisher="Elsevier Science Bv",
volume="840",
number="1-2",
pages="349--378",
abstract="We calculate the density matrix for the decay of a polarised top quark into a polarised W boson and a massive 17 quark, for the most general Wth vertex arising from dimension-six gauge-invariant effective operators. We show that, in addition to the well-known W helicity fractions, for polarised top decays it is worth defining and studying the transverse and normal W polarisation fractions, that is, the W polarisation alone two directions orthogonal to its momentum. In particular, a rather simple forward-backward asymmetry in the normal direction is found to be very sensitive to complex phases in one of the Wth anomalous couplings. This asymmetry, which indicates a normal W polarisation, can be generated for example by a P-odd. T-odd transition electric dipole moment. We also investigate the angular distribution of decay products in the top quark rest frame, calculating the spin analysing powers for a general Wth vertex. Finally we show that, using a combined fit to top decay observables and the t W cross section, at LHC it will be possible to obtain model-independent measurements of all the (complex) Wth couplings as well as the single top polarisation. Implications for spin correlations in top pair production are also discussed.",
optnote="ISI:000281832900013",
optnote="exported from refbase (https://references.ific.uv.es/refbase/show.php?record=370), last updated on Thu, 01 Nov 2012 19:53:07 +0000",
issn="0550-3213",
doi="10.1016/j.nuclphysb.2010.07.012",
opturl="http://arxiv.org/abs/1005.5382",
opturl="https://doi.org/10.1016/j.nuclphysb.2010.07.012",
archivePrefix="arXiv",
eprint="1005.5382",
language="English"
}