Flavor-singlet spectrum in multi-flavor QCD

TL;DR

This paper investigates the flavor-singlet spectrum in multi-flavor SU(3) gauge theories to understand strong dynamics and implications for composite Higgs models, using lattice simulations to compare different flavor configurations.

Contribution

It presents a comparative lattice study of flavor-singlet channels in SU(3) theories with multiple light flavors, focusing on the 8-flavor case and collaboration efforts to approach the massless limit.

Findings

Comparison of results from different collaborations on flavor-singlet spectra.

Insights into the hierarchy of scalar states relevant for composite Higgs models.

Progress towards understanding the massless limit in multi-flavor theories.

Abstract

Studying SU(3) gauge theories with increasing number of light fermions is relevant both for understanding the strong dynamics of QCD and for constructing strongly interacting extensions of the Standard Model (e.g. UV completions of composite Higgs models). In order to contrast these many-flavors strongly interacting theories with QCD, we study the flavor-singlet spectrum as an interesting probe. In fact, some composite Higgs models require the Higgs boson to be the lightest flavor-singlet scalar in the spectrum of a strongly interacting new sector with a well defined hierarchy with the rest of the states. Moreover, introducing many light flavors at fixed number of colors can influence the dynamics of the lightest flavor-singlet pseudoscalar. We present the on-going study of these flavor-singlet channels using multiple interpolating operators on high-statistics ensembles generated by the LatKMI collaboration and we compare results with available data obtained by the Lattice Strong Dynamics collaboration. For the theory with 8 flavors, the two collaborations have generated configurations that complement each others with the aim to tackle the massless limit using the largest possible volumes.