Abstract
Extensions of the Standard Model which address the hierarchy problem and dark matter (DM) often contain top partners and additional resonances at the TeV scale. We explore the phenomenology of a simplified effective model with a vector resonance $Z'$, a fermionic vector-like coloured partner of the top quark $T'$ as well as a scalar DM candidate $\phi$ and provide publicly available implementations in CalcHEP and MadGraph. We study the $pp \to Z' \to T'\overline{T'} \to t\bar{t}\,\phi\phi$ process at the LHC and find that it plays an important role in addition to the $T'\overline{T'}$ production via strong interactions. It turns out that the presence of the $Z'$ can provide a dominant contribution to the $t\bar{t}+E_T^{\text{miss}}$ signature without conflicting with existing bounds from $Z'$ searches in di-jet and di-lepton final states. We find that through this process, the LHC is already probing DM masses up to about 900 GeV and top partner masses up to about 1.5 TeV, thus exceeding the current bounds from QCD production alone almost by a factor of two for both particles.
Highlights
The Higgs boson discovery in July 2012 [1,2] was a remarkable celebration of the unprecedented success of the standard model (SM), which was missing this last particle
We explore the phenomenology of a simplified model, which incorporates these ingredients at the level of an effective theory with a vector resonance Z0 as a consequence of the TC and composite Higgs (CH) predictions of integer spin bound states, a fermionic vectorlike colored partner of the top quark T0 as well as a scalar dark matter candidate φ arising via minimal gauge-invariant Yukawa interactions λφT0t
We have explored the phenomenology of a simplified, effective model with a vector resonance Z0, a fermionic vectorlike colored partner of the top quark T0, which carries negative dark matter (DM) parity, and a scalar DM candidate φ—which we refer to as the ZP-TP-DM model
Summary
The Higgs boson discovery in July 2012 [1,2] was a remarkable celebration of the unprecedented success of the standard model (SM), which was missing this last particle. The Higgs boson is the bound state of new fundamental particles involved in these new strong dynamics, in spite of the qualitatively different nature, the Higgs properties can be similar to those of the SM Higgs and consistent with the LHC data [9] Another set of promising BSM theories are composite Higgs (CH) scenarios [10,11,12] (see recent developments starting from [13]), in which the new gauge dynamics do not break the electroweak symmetry, but spontaneously break a global symmetry of the high energy model [14].
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