Signatures of vector-like top partners decaying into new neutral scalar or pseudoscalar bosons
Journal article, 2020

We explore the phenomenology of models containing one Vector-Like Quark (VLQ), t′, which can decay into the Standard Model (SM) top quark, t, and a new spin-0 neutral boson, S, the latter being either a scalar or pseudoscalar state. We parametrise the underlying interactions in terms of a simplified model which enables us to capture possible Beyond the SM (BSM) scenarios. We discuss in particular three such scenarios: one where the SM state is supplemented by an additional scalar, one which builds upon a 2-Higgs Doublet Model (2HDM) framework and another which realises a Composite Higgs Model (CHM) through partial compositeness. Such exotic decays of the t′ can be competitive with decays into SM particles, leading to new possible discovery channels at the Large Hadron Collider (LHC). Assuming t′ pair production via strong interactions, we design signal regions optimised for one t′ → S t transition (while being inclusive on the other t¯ ′ decay, and vice versa), followed by the decay of S into the two very clean experimental signatures S → γ γ and S → Z (→ ℓ+ℓ−)γ. We perform a dedicated signal- to-background analysis in both channels, by using Monte Carlo (MC) event simulations modelling the dynamics from the proton-proton to the detector level. Under the assumption of BR(t′ → S t) = 100%, we are therefore able to realistically quantify the sensitivity of the LHC to both the t′ and S masses, assuming both current and foreseen luminosities. This approach paves the way for the LHC experiments to surpass current VLQ search strategies based solely on t′ decays into SM bosons (W±, Z , h). © 2020, The Author(s).

Top Quark

Technicolor and Composite Models


Higgs Physics

Beyond Standard Model

Heavy Quark Physics



R. Benbrik

Universite Cadi Ayyad

E. Bergeaas Kuutmann

Uppsala University

Diogo Buarque Franzosi

Chalmers, Physics, Subatomic and Plasma Physics

V. Ellajosyula

Uppsala University

R. Enberg

Uppsala University

Gabriele Ferretti

Chalmers, Physics, Subatomic, High Energy and Plasma Physics

M. Isacson

Uppsala University

Y. B. Liu

Henan Institute of Science and Technology

T. Mandal

Uppsala University

T. Mathisen

Uppsala University

S. Moretti

University of Southampton

L. Panizzi

Uppsala University

Journal of High Energy Physics

1126-6708 (ISSN) 1029-8479 (eISSN)

Vol. 2020 5 28

Solving the Higgs Fine-Tuning Problem with Top Partners

Knut and Alice Wallenberg Foundation, 2018-01-01 -- 2022-12-31.

Subject Categories

Accelerator Physics and Instrumentation

Subatomic Physics

Bioinformatics (Computational Biology)


Basic sciences



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