Light Custodians and Higgs Physics in Composite Models

Composite Higgs models involving partial compositeness of Standard Model fermions typically require the introduction of fermionic partners which are relatively light in realistic scenarios. In this paper, we analyze the role of these light custodian fermions in the phenomenology of the composite Higgs models and show that they significantly modify couplings of the Higgs field. We focus on the coupling to gluons in particular, which is of central importance for Higgs production at the LHC. We show that this coupling can be increased as well as decreased depending on the SM fermion embedding in the composite multiplets. We also discuss modification of the Higgs couplings to bottom and top quarks and show that modifications to all these three couplings Hgg, Htt, and Hbb are generically independent parameters.