Probing top-quark couplings indirectly at Higgs factoriesCZ is supported by IHEP (Y7515540U1); EV is supported by a Marie Skłodowska-Curie Individual Fellowship of the European Commission’s Horizon 2020 Programme (704187)

Durieux, Gauthier (DESY Notkestraße 85, D-22607, Hamburg, Germany) ; Gu, Jiayin (PRISMA Cluster of Excellence, Institut für Physik, Johannes Gutenberg-Universität, 55099 Mainz, Germany) ; Vryonidou, Eleni (Theoretical Physics Department, CERN, 1211 Geneva 23, Switzerland) ; Zhang, Cen (Institute of High Energy Physics, and School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China)

27 November 2018

Abstract: We perform a global effective-field-theory analysis to assess the combined precision of Higgs couplings, triple gauge-boson couplings, and top-quark couplings, at future circular e+e− colliders, with a focus on runs below the production threshold. Deviations in the top-quark sector entering as one-loop corrections are consistently taken into account in the Higgs and diboson processes. We find that future lepton colliders running at center-of-mass energies below the production threshold can still provide useful information on top-quark couplings, by measuring virtual top-quark effects. With rate and differential measurements, the indirect individual sensitivity achievable is better than at the high-luminosity LHC. However, strong correlations between the extracted top-quark and Higgs couplings are also present and lead to much weaker global constraints on top-quark couplings. This implies that a direct probe of top-quark couplings above the production threshold is also helpful for the determination of Higgs and triple-gauge-boson couplings. In addition, we find that below the production threshold, the top-quark Yukawa coupling can be determined by its loop corrections to all Higgs production and decay channels. Degeneracy with the ggh coupling can be resolved, and even a global limit is competitive with the prospects of a linear collider above the threshold. This provides an additional means of determining the top-quark Yukawa coupling indirectly at lepton colliders.

Published in: Chinese Phys. C 42 (2018) 123107
Published by: Institute of Physics Publishing/Chinese Academy of Sciences
DOI: 10.1088/1674-1137/42/12/123107
arXiv: 1809.03520
License: CC-BY-3.0

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