Decay and polarization properties of the top quark

Abstract

Polarization and angular distributions in the decay sequence $t\ensuremath{\rightarrow}b{W}^{+}$, ${W}^{+}\ensuremath{\rightarrow}{l}^{+}{\ensuremath{\nu}}_{l}$ are discussed for the standard model. Top quarks from ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}t\overline{t}$ are predicted to have large polarization but, even if not, the parity-violating effects in this decay chain are large and will test closely the detailed spin structure of the electroweak interactions involving the top quark. A means of analyzing $\overline{t}t$ decays following $\overline{t}t$ production in hadronic interactions is developed, leading to an illuminating construction. Its application is illustrated by the analysis of the candidate for top-antitop pair creation in $\overline{p}p$ collisions found by the Collider Detector at Fermilab (CDF) at 1.8 TeV center-of-mass energy. If this is really $\overline{t}t$ production, then the top-quark mass would be ${125}_{\ensuremath{-}11}^{+19}$ GeV/${\mathit{c}}^{2}$.