Testing topquark Yukawa interactions in e^{+}e^{}>tt¯Z
Abstract
The determination of the topquark Yukawa couplings in the process e^{+}e^{}>tt¯Z is studied for the high luminosity option (∫L=500 fb^{1}) of a linear e^{+}e^{} collider. Polarization of the electron beam is considered. The method of optimal observables is adopted to determine the couplings and to disentangle different models. It is found that it could be possible to discriminate between the standard model scalar Higgs boson, a pure pseudoscalar, and the Higgs boson of mixed CP at about the 12σ level for s=1. TeV for a Higgs boson mass slightly above twice the topquark mass both for the leptonic and hadronic topquark decay channels. However, the s=0.5 TeV collider turns out to have too small energy for tests of the topquark Yukawa coupling because of its limited production rate (at most a 2.5σ effect). Possible tests of CP violation in the scalar sector are considered.
 Publication:

Physical Review D
 Pub Date:
 December 1999
 DOI:
 10.1103/PhysRevD.60.115018
 arXiv:
 arXiv:hepph/9907206
 Bibcode:
 1999PhRvD..60k5018G
 Keywords:

 14.80.Cp;
 14.65.Ha;
 Nonstandardmodel Higgs bosons;
 Top quarks;
 High Energy Physics  Phenomenology
 EPrint:
 17 pages, references added, typos and a few minor imprecise comments corrected