Abstract
We evaluate the implications of LHC and LEP/SLC measurements for the electro-weak couplings of the top and bottom quarks. We derive global bounds on the Wilson coefficients of ten two-fermion operators in an effective field theory description. The combination of hadron collider data with Z -pole measurements is found to yield tight limits on the operator coefficients that modify the left-handed couplings of the bottom and top quark to the Z boson. We also present projections for the high-luminosity phase of the LHC and for future electron-positron colliders. The bounds on the operator coefficients are expected to improve substantially during the remaining LHC programme, by factors of 1 to 5 if systematic uncertainties are scaled as statistical ones. The operation of an e+e− collider at a center-of-mass energy above the top-quark pair production threshold is expected to further improve the bounds by one to two orders of magnitude. The combination of measurements in pp and e+e− collisions allows for a percent-level determination of the top-quark Yukawa coupling, that is robust in a global fit.
Highlights
With the discovery of the Higgs boson [1, 2] at the LHC, the particle content of the Standard Model (SM) is experimentally confirmed
We evaluate the implications of LHC and LEP/SLC measurements for the electro-weak couplings of the top and bottom quarks
The combination of hadron collider data with Z-pole measurements is found to yield tight limits on the operator coefficients that modify the left-handed couplings of the bottom and top quark to the Z boson
Summary
With the discovery of the Higgs boson [1, 2] at the LHC, the particle content of the Standard Model (SM) is experimentally confirmed. As the top quark escaped scrutiny at the previous generation of electron-positron colliders, the LHC measurements analyzed in this paper provide the first constraints on its EW couplings. We include measurements in bottom-quark pair production at LEP and SLC in the fit. Operation above the top-quark pair production threshold is part of the initial stage of the CLIC project [16] and later stages of the ILC and FCCee. In this paper the potential of operation at a center-of-mass energy of 500 GeV is studied, where very tight constraints on the top-quark operators are expected [6, 17]. We present the first comparison of the HL-LHC and ILC [11] potential for precision measurements that constrain the top and bottom-quark EW couplings.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
