The model dependence of $m_\varrho / f_π$

Abstract

Should a strongly coupled composite Higgs boson scenario be realized in Nature the most easily accessible experimental signal would be new particles made up of the same ingredients as the Higgs but with different quantum numbers. The lightest of these hypothetical new particles would probably be the vector mesons. In this contribution we report results on m ρ / f π in the chiralcontinuum limit with SU(3) gauge group and N f = 2, 3, 4, 5, 6 flavors of fundamental fermions. In addition we compare m ρ / f π results from various models with different gauge groups and fermion content. The main conclusion seems to be that the experimental measurement of this vector meson mass will be able to distinguish between gauge groups but less so between the fermion content.

More on the flavor dependence of $m_\varrho / f_π$

“…Applied to composite Higgs models inspired by strong dynamics, this would mean that a potential measurement of a new so far unobserved vector resonance inherent in these types of models, would not select the flavor number. The measured vector mass would rather place constraints on the gauge group [48].…”

Mesonic decay constant and mass ratios and the conformal window

“…In order to compare with the lattice results we would need 𝑓 𝑉 , however only 𝑓 𝑃𝑆 was measured directly [22][23][24]. Here we use the KSRF relation 𝑓 𝑉 = √ 2 𝑓 𝑃𝑆 originating in vector meson universality to estimate 𝑓 𝑉 and assign a 12% uncertainty which holds in QCD.…”

“…In this contribution a new approach is proposed [21]: by matching the fully controlled lattice results obtained for low fermion numbers [22][23][24] and fully controlled perturbative results obtained close to but below 𝑁 𝑓 = 16.5 where asymptotic freedom is still present. The latter calculation will be the focus of our contribution.…”

“…Figure1: Left: the 𝑓 𝑉 /𝑚 𝑉 ratio in increasing perturbative order. The non-perturbative result from combined lattice calculations[22][23][24] and the KSRF-relation is also shown. The smaller error band corresponds to the uncertainty of the lattice calculation, the wider one combines this with a conservative estimate of the uncertainty of the KSRF-relation itself.…”