SU(2) Gauge Theory with Two Fundamental Flavours: a Minimal Template for Model Building

Preprint number: CP3-Origins-2016-6 DNRF90 and DIAS-2016-6
Authors: Rudy Arthur (CP3-Origins & DIAS), Vincent Drach (CERN), Martin Hansen (CP3-Origins & DIAS), Ari Hietanen (CP3-Origins & DIAS), Claudio Pica (CP3-Origins & DIAS), and Francesco Sannino (CP3-Origins & DIAS)
External link: arXiv.org

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We investigate the continuum spectrum of the SU(2) gauge theory with Nf=2 flavours of fermions in the fundamental representation. This model provides a minimal template which is ideal for a wide class of Standard Model extensions featuring novel strong dynamics that range from composite (Goldstone) Higgs theories to several intriguing types of dark matter candidates, such as the SIMPs. We improve our previous lattice analysis by adding more data at light quark masses, at two additional lattice spacings, by determining the lattice cutoff via a Wilson flow measure of the w0 parameter, and by measuring the relevant renormalisation constants non-perturbatively in the RI’-MOM scheme. Our results for the lightest isovector states in the vector and axial channels, in units of the pseudoscalar decay constant, are m_V/F_PS∼13.1(2.2) and m_A/F_PS∼14.5(3.6) (combining statistical and systematic errors).
In the context of the composite (Goldstone) Higgs models, our result for the spin-one resonances are m_V>3.2(5) TeV and m_A>3.6(9) TeV, which are above the current LHC constraints. In the context of dark matter models, for the SIMP case our results indicate the occurrence of a compressed spectrum at the required large dark pion mass, which implies the need to include the effects of spin-one resonances in phenomenological estimates.