2012/01/30 by S. Fajfer, Fajfer, S., J. Drobnak +3
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #hep-ph
paper · pdf · doi:10.48550/arxiv.1201.6225
4 pages, to appear in the proceedings of XXIst International Europhysics Conference on High Energy Physics, Grenoble 2011
arxiv created 2012/01/30 · arxiv updated 2012/01/31
The most general set of new physics effective operators contributing to the decay of an unpolarized top quark into a bottom quark and a W gauge boson are considered at next-to-leading order in QCD. We find that the dipole operator contribution to the transverse-plus W helicity fraction F+ is enhanced compared to the leading order result at non-vanishing bottom quark mass. Nonetheless, presently the observable most sensitive to new physics contributions is the longitudinal W helicity fraction FL. We also investigate constraints on t W b couplings coming from precision flavor observables, in particular from Delta B=1 and Delta B=2 transitions of Bq mesons. We find these to be mostly superior to present direct constraints coming from top decay and single top production measurements at the LHC and Tevatron.