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Novel view of the flavor-singlet spectrum from multi-flavor QCD on the lattice

Yasumichi Aoki1, Tatsumi Aoyama2, Ed Bennett3, Toshihide Maskawa4,*, Kohtaroh Miura5, Hiroshi Ohki6, Enrico Rinaldi7, Akihiro Shibata8, Koichi Yamawaki4 et al. (LatKMI Collaboration)

Koichi Yamawaki4 and Takeshi Yamazaki9,10 (LatKMI Collaboration)

  • *Deceased.
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Phys. Rev. D 112, 114503 – Published 3 December, 2025

DOI: https://doi.org/10.1103/vnml-g6nx

Abstract

SU(3) gauge theories with an increasing number of light fermions are the templates of strongly interacting sectors and studying their low-energy dynamics and spectrum is important, both for understanding the strong dynamics of QCD itself, and for discovering viable UV completions of beyond the Standard Model physics. In order to contrast many-flavor strongly interacting theories with QCD on a quantitative footing, we use lattice field theory simulations. We focus on the study of the flavor-singlet spectrum in the scalar and pseudoscalar channels: This is an interesting probe of the dynamics of the strongly interacting sector, as reminded by the QCD case with the f0(500) (σ) and η′ mesons. The hierarchy of the spectrum of a strongly coupled new gauge sector of the Standard Model defines the potential reach of future colliders for new physics discoveries. In addition to a novel hierarchy with light scalars, introducing many light flavors at fixed number of colors can influence the dynamics of the lightest flavor-singlet pseudoscalar. We present a complete lattice study of both of these flavor-singlet channels on high-statistics gauge ensembles generated by the LatKMI Collaboration with 4, 8, and 12 copies of light mass-degenerate fermions. We also present other hadron masses on the lightest ensemble for Nf=8 generated by the LatKMI Collaboration and discuss the chiral extrapolation of the spectrum in this particular theory. We contrast the results to Nf=4 simulations and previous results of Nf=12 simulations.

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Phys. Rev. D 112, 114503– Published 3 December, 2025
  • Received 15 May 2025
  • Accepted 6 October 2025
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