Abstract
We consider contributions of nonstandard effective operators to the decay of an unpolarized top quark into a bottom quark and a gauge boson at next-to-leading order in QCD. We find that contribution to the transverse-plus helicity fraction () is significantly enhanced compared to the leading order result at nonvanishing bottom quark mass. Nonetheless, presently the most sensitive observable to direct contributions is the longitudinal helicity fraction . In particular, the most recent CDF measurement of already provides the most stringent upper bound on contributions, even when compared with indirect bounds from the rare decay .
- Received 26 October 2010
DOI:https://doi.org/10.1103/PhysRevD.82.114008
© 2010 The American Physical Society