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Real singlet scalar benchmarks in the multi-TeV resonance regime

Ian M. Lewis1,*, Jacob L. Scott1,†, Miguel A. Soto Alcaraz1,‡, and Matthew Sullivan2,§

  • *Contact author: ian.lewis@ku.edu
  • †Contact author: jacob.scott@ku.edu
  • ‡Contact author: msoto1@ku.edu
  • §Contact author: msullivan1@bnl.gov
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Phys. Rev. D 112, 095024 – Published 17 November, 2025

DOI: https://doi.org/10.1103/n5rt-jvg3

Abstract

Scalar extensions of the Standard Model (SM) are of much interest at the Large Hadron Collider (LHC) and future colliders. In particular, these models can give rise to resonant di-Higgs production and alter the Higgs trilinear coupling. In this paper, we study di-Higgs production in the Standard Model extended by a real scalar singlet with no additional symmetries. We determine how large the resonant di-Higgs rate and variation in the Higgs trilinear coupling can be in four scenarios: current LHC results and projected results at the high luminosity LHC (HL-LHC), the HL-LHC combined with a circular e−e+ collider such as the Circular Electron Positron Collider or Future Circular Collider with electron-positron collisions, and the HL-LHC combined with a linear e−e+ collider such as the International Linear Collider. While these are updated results from a previous study by [I. M. Lewis and M. Sullivan, Benchmarks for double Higgs production in the singlet extended standard model at the LHC, Phys. Rev. D 96, 035037 (2017).] using current LHC data, we go further and find benchmark points in the multi-TeV resonance regime for future colliders beyond the HL-LHC. Considering current LHC results, the resonant di-Higgs rate can still be an order of magnitude larger than the SM predicted di-Higgs rate. In the HL-LHC scenario, the Higgs trilinear coupling can still be a factor of three larger than the SM prediction for resonance masses in the 1.5–3.5 TeV range, where resonant searches may have less reach. This enhancement is just at the projected 2σ sensitivity of the HL-LHC. We find there are resonance masses for which the change in the Higgs trilinear is maximized while the resonant rate is negligible. We provide an analytical understanding of these effects with a discussion on the interplay of various constraints on the parameter space and the Higgs trilinear coupling.

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Phys. Rev. D 112, 095024– Published 17 November, 2025
  • Received 18 October 2024
  • Accepted 22 August 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

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