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张仁友 （ 南昌， 2010-04-17 ） 中国科学技术大学粒子物理与技术中心

Precise measurement of top-quark gauge couplings at high energy colliders. 张仁友 （ 南昌， 2010-04-17 ） 中国科学技术大学粒子物理与技术中心. Linear colliders: Hadron colliders:. ILC. Vff effective vertex:.

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张仁友 （ 南昌， 2010-04-17 ） 中国科学技术大学粒子物理与技术中心

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  1. Precise measurement of top-quark gauge couplings at high energy colliders 张仁友 （南昌，2010-04-17） 中国科学技术大学粒子物理与技术中心

  2. Linear colliders: • Hadron colliders: ILC

  3. Vff effective vertex: Possible anomalous couplings of the top quark to gauge bosons can be parameterized by means of an effective Lagrangian. chirality conserving dimension 4 operators (2) chirality flipping dimension 5 operators (8)

  4. radiative corrections in a renormalizable theory dimension 5 operators The operators associated to gE, gS, gTE and gTS are odd under a CP transformation ! Contribute to CP-violating observables !

  5. on-shell approximation: V is on-shell / couples to effective massless fermions both top quarks are on-shell [ ] related to (weak) magnetic and (weak) electric dipole moments Tree level results in the SM !

  6. 1-loop corrections : expressed in terms of the physical W and Z masses

  7. SM: ttV production at linear/hadron colliders: off-shell In technicolor and other models with a strongly coupled Higgs sector, anomalous top quark couplings may be induced at the 5-10% level. Beyond the SM: It is important to improve the theoretical prediction in order to accommodate the experimental measurement !

  8. main channel: We can measure the ttV couplings in top pair production with a few-percent precision. hep-ph/0106315

  9. Detectable values of the (weak) electric dipole moments would be evidence for a new type CP-violating interaction. Depending on how these form factors vary with s, their contribution to the cross section or to other observables can increase with the c.m. energy !

  10. The angular distributions and the angular and energy distributions of top-quark decay products provide very efficient tools for studying top-quark gauge couplings at linear colliders.

  11. Phys.Rev.D71,054013

  12. Tevatron 68.3% CL 95% CL

  13. LHC

  14. Tevatron : LHC :

  15. QCD corrections !

  16. 1-loop QCD corrections :

  17. input parameters: (theor.) (exp.) cuts: Tevatron LHC

  18. scale dependence: LHC Tevatron 1. The NLO QCD corrections reduce obviously the dependence of the cross section on the renormalization/factorization scale !

  19. PT distribution: 2. The NLO QCD corrections enhance significantly the PT distribution for the LHC, but make only a small impact on the differential cross section for the Tevatron !

  20. K-factor: top-quark charge asymmetry: Phys.Rev.D80,014022

  21. 1-loop QCD corrections : 1.35 1.09 pb 0.808 pb uncertainty: 11% (LO) Phys.Lett.B666,62 25-35% (NLO)

  22. Phys.Rev.D78,094010

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