Interplay of vector-like top partner multiplets in a realistic mixing set-up

Abstract

The ATLAS and CMS collaborations at the LHC have performed analyses on the existing data sets, studying the case of one vector-like fermion or multiplet coupling to the standard model Yukawa sector. In the near future, with more data available, these experimental collaborations will start to investigate more realistic cases. The presence of more than one extra vector-like multiplet is indeed a common situation in many extensions of the standard model. The interplay of these vector-like multiplet between precision electroweak bounds, flavour and collider phenomenology is a important question in view of establishing bounds or for the discovery of physics beyond the standard model. In this work we study the phenomenological consequences of the presence of two vector-like multiplets. We analyse the constraints on such scenarios from tree-level data and oblique corrections for the case of mixing to each of the SM generations. In the present work, we limit to scenarios with two top-like partners and no mixing in the down-sector.

Search for single production of vector-like top partner decaying to Wb at $$e\gamma $$ e γ collision

“…Generally, the top partner couplings to the SM particles are severely constrained by electroweak precision physics as well as by the direct measurement of V tb [25]. However, such constraints can be altered significantly in most realistic models including the vector-like quark with two or more partner multiplets [26][27][28][29][30][31][32][33]. Here we take a conservative limit for the coupling parameter g * ≤ 0.5, which is consistent with the current experiment bounds [34].…”

New vector-like fermions and flavor physics

“…(For some recent studies of constraints on some of these models, see, e.g., refs. [18][19][20].) For upper bounds on lepton flavor violating processes we quote bounds at 90% CL, as do most experiments, whereas for other measurements we quote the 1σ limits that are approximately 84% CL as one-sided bounds for Gaussian distributions.…”

“…The LHCb-CMS combination of their measurements, Br(B s → µ + µ − ) = (2.8 +0.7 −0.6 ) × 10 −9 , is quoted as the SM prediction times 0.76 +0. 20 −0.18 [44]. The 1σ range of the measured B s → µ + µ − rate is slightly outside the SM and corresponds to the region, 0.96 > |1 + c sigma regions of BSM parameter space are plotted in figure 2 using variables very similar to figure 1.…”

The LHC potential of vector-like quark doublets

“…The latter features an exotic charged bottom-partner, and we will consider its phenomenology in a follow-up work. A detailed account of the Yukawa structure and mixing patterns can be found in [46]. In the remaining of this section we will consider, in detail, the relation between the general formalism we use in this paper and composite (pseudo-Nambu-Goldstone) Higgs models.…”