$SU(2)$ Gauge Theory with Two Fundamental Flavours: Scalar and Pseudoscalar Spectrum

TL;DR

This study uses non-perturbative lattice simulations to estimate the masses of scalar and pseudoscalar particles in an $SU(2)$ gauge theory with two fundamental fermion flavors, informing composite Higgs and dark matter models.

Contribution

First benchmark estimates of light scalar and pseudoscalar masses in $SU(2)$ gauge theory with two flavors, including disconnected contributions, relevant for beyond Standard Model physics.

Findings

Mass ratios: $m_{a_0}/F_{PS}=16.7(4.9)$, $m_\sigma/F_{PS}=19.2(10.8)$, $m_{\eta'}/F_{PS}=12.8(4.7)$

Provided crucial data for composite Higgs and dark matter models

Included estimates of disconnected contributions in mass calculations

Abstract

We investigate the scalar and pseudoscalar spectrum of the $SU(2)$ gauge theory with $N_f=2$ flavours of fermions in the fundamental representation using non perturbative lattice simulations. We provide first benchmark estimates of the mass of the lightest $0(0^{+})$ ($\sigma$), $0(0^{-})$ ($\eta'$) and $1(0^+)$ ($a_0$) states, including estimates of the relevant disconnected contributions. We find $m_{a_0}/F_{\rm{PS}}= 16.7(4.9)$, $m_\sigma/F_{\rm{PS}}=19.2(10.8)$ and $m_{\eta'}/F_{\rm{PS}} = 12.8(4.7)$. These values for the masses of light scalar states provide crucial information for composite extensions of the Standard Model from the unified Fundamental Composi te Higgs-Technicolor theory \cite{Cacciapaglia:2014uja} to models of composite dark matter.