Abstract
We generalize the basis of CP-even chiral effective operators describing a dynamical Higgs sector, to the case in which the Higgs-like particle is light. Gauge and gauge-Higgs operators are considered up to mass dimension five. This analysis completes the tool needed to explore at leading order the connection between linear realizations of the electroweak symmetry breaking mechanism — whose extreme case is the Standard Model — and non-linear realizations with a light Higgs-like particle present. It may also provide a model-independent guideline to explore which exotic gauge-Higgs couplings may be expected, and their relative strength to Higgsless observable amplitudes. With respect to fermions, the analysis is reduced by nature to the consideration of those flavor-conserving operators that can be written in terms of pure-gauge or gauge-Higgs ones via the equations of motion, but for the standard Yukawa-type couplings.
Highlights
A new resonance at the Electroweak (EW) scale has been established at LHC [1, 2], consistent with the hypothesis of the SM scalar boson [3,4,5] with mass around 125 GeV.There are essentially two main frameworks that have been proposed to explain the EW symmetry breaking sector
In such a framework some strong dynamics should intervene at a scale Λs, and the characteristic scale of the associated Goldstone bosons f respects Λs ≤ 4πf [6]
In the original formulation [7,8,9] the physical Higgs particle is removed from the low-energy spectrum and only the three would-be-Goldstone bosons are retained, in order to give masses to the weak gauge bosons, with f = v, where v = 246 GeV denotes the electroweak scale defined via the W mass, MW = gv/2
Summary
A new resonance at the Electroweak (EW) scale has been established at LHC [1, 2], consistent with the hypothesis of the SM scalar boson (so-called “Higgs boson” for short hereafter) [3,4,5] with mass around 125 GeV. [10,11,12,13,14,15], the SM Higgs particle is substituted by a composite scalar degree of freedom that, being a quasi-Goldstone boson of a larger symmetry group, cannot acquire a large (i.e. O(TeV)) mass1 Besides this light Higgs-like scalar particle, these models still present a strongly interacting sector at the TeV scale, while they may correct at lower energies the size of SM couplings. This path looks promising in the absence of new resonances in LHC data. This analysis enlarges and completes the operator basis previously considered in Refs. [17,18,19,20,21,22,23]
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