Abstract
We exploit all LHC available Run 2 data at center-of-mass energies of 8 and 13 TeV for searches for physics beyond the Standard Model. We scrutinize the allowed parameter space of Little Higgs models with the concrete symmetry of T -parity by providing comprehensive analyses of all relevant production channels of heavy vectors, top partners, heavy quarks and heavy leptons and all phenomenologically relevant decay channels. Constraints on the model, particularly the symmetry breaking scale f, will be derived from the signatures of jets and missing energy or leptons and missing energy. Besides the symmetric case, we also study the case of T-parity violation. Furthermore, we give an extrapolation to the LHC high-luminosity phase at 14 TeV as well.
Highlights
No further degrees of freedom in the range up to a TeV
In this paper we consider the Littlest Higgs Model with T -parity (LHT) model just as such an effective field theory consisting of the SM degrees of freedom augmented by (T -odd) heavy vector bosons, heavy quarks as well as additional heavy pseudo-Nambu-Goldstone boson (pNGB)
There are two reasons for that: first, in the context of strongly interacting UV completions T parity violation can naturally occur via an anomalous Wess-Zumino-Witten term, [15, 16], secondly, there is a certain tension for the case that the lightest T -odd particle, the heavy photon AH is absolutely stable from relic density calculations and direct detection dark matter experiments [17, 18]
Summary
The Littlest Higgs model [8] is based on a non-linear sigma model with a single field Σ parameterizing a SU(5)/SO(5) symmetry breaking structure. The vacuum expectation value (vev) causing the breaking from SU(5) to SO(5), Σ0, can be cast into the form of the 5 × 5 matrix. Like many other BSM models, the Littlest Higgs model suffers from constraints by electroweak precision observables, as the mass of the heavy hypercharge boson, AH , has an accidentally small prefactor, cf the right hand side of eq (2.10). To alleviate these constraints, a discrete symmetry, TeV- or short T -parity has been added [13, 14], which phenomenologically plays a similar role as R-parity in supersymmetry (SUSY). The mass spectrum for heavy T -odd fermions is given (at order O(v2/f 2)) by
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