Low-energy signals of strongly-coupled electroweak symmetry-breaking scenarios

Abstract

The non-observation of new particles at the LHC suggests the existence of a mass gap above the electroweak scale. This situation is adequately described through a general electroweak effective theory with the established fields and Standard Model symmetries. Its couplings contain all information about the unknown short-distance dynamics which is accessible at low energies. We consider a generic strongly-coupled scenario of electroweak symmetry breaking, with heavy states above the gap, and analyze the imprints that its lightest bosonic excitations leave on the effective Lagrangian couplings. Different quantum numbers of the heavy states imply different patterns of low-energy couplings, with characteristic correlations which could be identified in future data samples. The predictions can be sharpened with mild assumptions about the ultraviolet behaviour of the underlying fundamental theory.

Fingerprints of heavy scales in electroweak effective Lagrangians

“…The P -even contributions to the first column of table 6 agree with the results obtained previously in ref. [12]. The low-energy contributions from exotic J P C = 1 +− heavy states were analyzed in a similar way in ref.…”

“…The bosonic LECs in the first column were already presented in ref. [12]. The triplet scalar field only contributes to the four-fermion operators O ψ 4 1 and O ψ 4 3 , while…”

“…Similar studies have been done before for specific weakly-coupled models of new physics [83][84][85][86][87][88][89][90], within the much simpler linear framework with a SM doublet Higgs; in some cases, even at the one-loop level [91][92][93][94][95][96][97][98][99][100] in the usual perturbative expansion in powers of small couplings. However, the LECs of the generic non-linear EWET have remained largely unexplored until now [12,72,73].…”

“…Our operator basis is given in table 1 [12]. 11 Once the auxiliary fields are forced to take the values in eqs.…”

“…The values of the bosonic LECs in table 8 agree with the results found previously in ref. [12], which only considered P -even operators and exact custodial symmetry. The couplings which do not contain Higgs fields are also in agreement with those found in QCD through the large-N C matching of Resonance Chiral Theory and χPT [13,14] , while a singlet pseudoscalar can only be spotted through O ψ 4 4 .…”