  The existence of a mass gap between the Standard Model (SM) and possible new
states encourages us to use effective field theories. Here we follow the
non-linear realization of the electroweak symmetry breaking: the electroweak
effective theory (EWET), also known as Higgs effective field theory (HEFT) or
electroweak chiral Lagrangian (EWChL). At short distances an effective
resonance Lagrangian which couples the SM states to bosonic and fermionic
resonances is considered. After integrating out the resonances and assuming a
well-behaved high-energy behavior, we estimate or bound purely bosonic
low-energy constants in terms of only resonance masses. Current experimental
information on these low-energy constants allows us to constrain the
high-energy resonance masses.
