We study how to probe the anomalous CP-violating couplings of the top quark with γ, Z, and g in the tt̄ threshold region at future e+e- colliders. These couplings contribute to the difference of the t and t̄ polarization vectors δP and to the CP-odd spin-correlation tensor δQij. We find that typical sizes of δP and δQij are 5-20% times the couplings (dtγ,dtZ,dtg) in the threshold region. Experimentally δP can be measured efficiently using the CP-odd combination of the l± momenta or of the l± directions. We have similar sensitivities to both the real and imaginary parts of the couplings independently using the two components of δP. Taking advantage of different dependences of δP on the e± polarizations and on the c.m. energy, we will be able to disentangle the effects of the three couplings dtγ,dtZ,dtg in the tt̄ threshold region. We give rough estimates of sensitivities to the anomalous couplings expected at future e+e- colliders. The sensitivities to dtγ and dtZ are comparable to those attainable in the open-top region at e+e- colliders. The sensitivity to dtg is worse than that expected at a hadron collider but exceeds the sensitivity in the open-top region at e+e- colliders.
|ジャーナル||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|出版ステータス||Published - 2000 7 1|
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