Abstract
In composite Higgs models with partial compositeness, the small value of the observed Higgs mass implies the existence of light fermionic resonances, the top partners, whose quantum numbers are determined by the symmetry (and symmetry breaking) structure of the theory. Here we study light top partners with electric charge 8/3, which are predicted, for instance, in some of the most natural composite Higgs realizations. We recast data from two same sign lepton searches and from searches for microscopic blackholes into a bound on its mass, M8/3 > 940 GeV. Furthermore, we compare potential reach of these searches with a specifically designed search for three same-sign lepton, both at 8 and 14 TeV. We provide a simplified model, suitable for collider analysis.
Highlights
The study of the (3,3)2/3 is in particular motivated by results obtained in a certain class of holographic 5D Composite Higgs models, where this multiplet is found to be the lightest [53]
In composite Higgs models with partial compositeness, the small value of the observed Higgs mass implies the existence of light fermionic resonances, the top partners, whose quantum numbers are determined by the symmetry structure of the theory
We propose a simplified scenario with only the charge-8/3 state in the spectrum and just two free parameters. This approximation is suitable for a collider study, and we use it to compare the sensitivity of different searches based on final states with two or three same-sign leptons
Summary
We propose a simplified model in which only one colored resonance X8/3 with electric charge 8/3 and mass M8/3 is present beyond the SM. In scenarios where only the multiplet containing the X8/3 is present in the low energy spectrum, as we consider in this work, the top quark in the eq (2.1) is right-handed This assumption, which we will adopt for this simplified model, has a non-negligible impact on the phenomenology. W ’s decay leptonically about 2/9 of the times (more if one includes leptonic τ decays) so that X8/3X8/3 decays produce at least two same-sign leptons (2ssl) approximately 1/4 of the times — almost three times more than charge-5/3 resonances This implies that the background can be efficiently suppressed and the signal acceptance pushed to relatively large values. With a probability of ∼ 2%, the X8/3 decays into 3 leptons with the same charge (3ssl) This is a novel and distinctive signature, with practically vanishing background, that can potentially provide a new sensitive channel to search for X8/3. We recast one of the most up-to-date 2ssl searches [48, 49] into bounds on M8/3, using the simplified model described above, and we compare the sensitivity of 2ssl with 3ssl searches, both at 8 and 14 TeV, and identify the best strategy to search for charge-8/3 resonances at the LHC
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