Constraints from Triple Gauge Couplings on Vectorlike Leptons

Abstract

We study the contributions of colorless vectorlike fermions to the triple gauge couplings $W^{+}{W}^{-}\gamma$ and $W^{+}{W}^{-}{Z}^0$. We consider models in which their coupling to the Standard Model Higgs boson is allowed or forbidden by quantum numbers. We assess the sensitivity of the future accelerators FCC-ee, ILC and CLIC to the parameters of these models, assuming they will be able to constrain the anomalous triple gauge couplings with a precision $\delta {\kappa }_V\sim \mathcal{O}(10^{-4})$, $V=\gamma ,Z^0$. We show that the combination of measurements at different center-of-mass energies helps to improve the sensitivity to the contribution of vectorlike fermions, in particular when they couple to the Higgs. In fact, the measurements at the FCC-ee and, especially, the ILC and the CLIC, may turn the triple gauge couplings into a new set of precision parameters able to constrain the models better than the oblique parameters or the $H\to \gamma \gamma$ decay, even assuming the considerable improvement of the latter measurements achievable at the new machines.

Matches version published in PRD. Some references added and LHC limits included

References in corpus (6)

• The global electroweak fit at NNLO and prospects for the LHC and ILC
• ILC Operating Scenarios
• Search for vector-like T quarks decaying to top quarks and Higgs bosons in the all-hadronic channel using jet substructure
• Search for electroweak production of charginos and neutralinos in WH events in proton-proton collisions at sqrt(s) = 13 TeV
• CLIC e+e- Linear Collider Studies
• Measurement of the Z gamma production cross section in pp collisions at 8 TeV and search for anomalous triple gauge boson couplings