Effective field theory and scalar extensions of the top quark sector

Englert, C. , Galler, P. and White, C. (2020) Effective field theory and scalar extensions of the top quark sector. Physical Review D, 101, 035035. (doi: 10.1103/PhysRevD.101.035035)

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Effective field theory (EFT) approaches are widely used at the Large Hadron Collider (LHC), such that it is important to study their validity and ease of matching to specific new physics models. In this paper, we consider an extension of the Standard Model (SM) in which a top quark couples to a new heavy scalar. We find the dimension six operators generated by this theory at low energy and match the EFT to the full theory up to the next-to-leading order (NLO) precision in the simplified model coupling. We then examine the range of validity of the EFT description in top pair production, finding excellent validity even if the scalar mass is only slightly above LHC energies, provided NLO corrections are included. In the absence of the latter, the LO EFT overestimates kinematic distributions, such that overoptimistic constraints on beyond the Standard Model (BSM) contributions are obtained. We next examine the constraints on the EFT and full models that are expected to be obtained from both top pair and four top production at the LHC, finding for low scalar masses that both processes show similar exclusion power. However, for larger masses, estimated LHC uncertainties push constraints into the nonperturbative regime, where the full model is difficult to analyze, and thus is not perturbatively matchable to the EFT. This highlights the necessity to improve uncertainties of SM hypotheses in top final states.

Item Type:Articles
Additional Information:This work was supported by the Munich Institute for Astro- and Particle Physics (MIAPP) of the DFG Excellence Cluster Origins (www.origins-cluster.de). CE and PG are supported by the UK Science and Technology Facilities Council (STFC), under grant ST/P000746/1. CDW is supported by the STFC, under grant ST/P000754/1, and by the European Union Horizon 2020 research and innovation programme under the Marie Sk lodowska-Curie grant agreement No. 764850
Glasgow Author(s) Enlighten ID:Galler, Dr Peter and White, Dr Christopher and Englert, Professor Christoph
Authors: Englert, C., Galler, P., and White, C.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Physical Review D
Publisher:American Physical Society
ISSN (Online):2470-0029
Copyright Holders:Copyright © 2020 the American Physical Society
First Published:First published in Physical Review D 101:035035
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
173809Phenomenology from Lattice QCD and Collider PhysicsChristine DaviesScience and Technology Facilities Council (STFC)ST/P000746/1P&S - Physics & Astronomy