A first top partner hunter’s guide

Abstract

We provide a systematic effective lagrangian description of the phenomenology of the lightest top-partners in composite Higgs models. Our construction is based on symmetry, on selection rules and on plausible dynamical assumptions. The structure of the resulting simplified models depends on the quantum numbers of the lightest top partner and of the operators involved in the generation of the top Yukawa. In all cases the phenomenology is conveniently described by a small number of parameters, and the results of experimental searches are readily interpreted as a test of naturalness. We recast presently available experimental bounds on heavy fermions into bounds on top partners: LHC has already stepped well inside the natural region of parameter space.

What is the γγ resonance at 750 GeV?

“…First, the need for a rich operator structure to accommodate flavour suggests the number of degrees of freedom should be large (N 1). Also the observed value of the Higgs mass is naturally obtained in composite Higgs models for g * ∼ 2-4 [52]. Finally, the slight excess in di-bosons at around 2 TeV in LHC Run 1 can be explained as the production of vector resonances again provided g * ∼ 3 (one must however be aware that no corresponding excess is observed at run2, even though the integrated luminosity is not yet sufficient to deem the run1 excess a fluctuation).…”

Anomalous gauge couplings from composite Higgs and warped extra dimensions

“…For a given G, there is also a freedom to choose the embedding of the composite fermions with which the elementary fermion mixes. The top sector plays a central role in this scenario, as a natural realization requires a composite top partner lighter than the mass scale of the strong sector (see e.g [14]). A composite Higgs model is described by an effective chiral Lagrangian, and contains in general many free continuous parameters.…”

Single production of an exotic bottom partner at LHC

“…[30] present experimental searches are not sensitive to single production of third generation partners. This is the case with searches for single production of a new quark which decays to one b-jet and a W .…”

“…Recently, the authors of ref. [30] have reassessed these limits for the case of Pseudo Goldstone Boson Higgs, showing that in some cases one can exclude top partners with masses up to 1.5 TeV. For such masses, single production of exotic quarks, although usually being electroweak (EW) suppressed, starts being competitive with double production [31].…”