After the discovery of the Higgs-like boson by the LHC 2012 it is the most important task to check whether this new particle is the Standard Model Higgs boson or something else. In this paper, we study whether the 125 GeV boson could be the pseudo-Goldstone boson of Little Higgs models. We derive limits on the parameter space of several Little Higgs models (simple group and product group models, with and without T-parity), both from the experimental data from ATLAS and CMS about the different Higgs discovery channel and the electroweak precision observables. We perform a fit of several Little Higgs models to all electroweak parameters from measurements of SLC, LEP, Tevatron, and LHC. For the Higgs searches, we include all available data from the summer conferences in 2012 as well as the updates from December 2012. We show that there always exists a region in the parameter space of the models under consideration where the measured chi^2 is equal or lower than the SM chi^2: a closer look at the minimum chi^2 will however reveal that the agreement with the collected data is not significantly better as within the SM. While for the models without T-parity the Little Higgs scale f is forced to be of the order 2-4 TeV in order to be compatible with the collected data, in the models with T-parity the scale f is constrained to be only above O(500) GeV, reducing the amount of fine-tuning. We also show that these results are still driven by the electroweak precision measurements due to the bigger LHC dataComment: 40 pages, 6 figure

The Littlest Higgs model with T-parity is providing an attractive solution to the fine-tuning problem. This solution is only entirely natural if its intrinsic symmetry breaking scale f is relatively close to the electroweak scale. We examine the constraints using the latest results from the 8 TeV run at the LHC. Both direct searches and Higgs precision physics are taken into account. The constraints from Higgs couplings are by now competing with electroweak precision tests and both combined exclude f up to 694 GeV or 560 GeV depending on the implementation of the down-type Yukawa sector. Direct searches provide robust and complementary limits and constrain f to be larger than 638 GeV. We show that the Littlest Higgs model parameter space is slowly driven into the TeV range. Furthermore, we develop a strategy on how to optimise present supersymmetry searches for the considered model, with the goal to improve the constraints and yield more stringent limits on f .

In this paper we study the discovery potential of the LHC run II for heavy vector-like top quarks in the decay channel to a top and a Z boson. Despite the usually smaller branching ratio compared to charged-current decays, this channel is rather clean and allows for a complete mass reconstruction of the heavy top. The latter is achieved in the leptonic decay channel of the Z boson and in the fully hadronic top channel using boosted jet and jet substructure techniques. To be as model-independent as possible, a simplified model approach with only two free parameters has been applied. The results are presented in terms of parameter space regions for 3σ evidence or 5σ discovery for such new states in that channel.

The status of several prominent model implementations of the Little Higgs paradigm, the Littlest Higgs with and without discrete T-parity as well as the Simplest Little Higgs are reviewed. For this, we are taking into account a fit of 21 electroweak precision observables from LEP, SLC, Tevatron together with the full 25 fb −1 of Higgs data reported by ATLAS and CMS. For the Littlest Higgs with T-parity an outlook on corresponding direct searches at the 8 TeV LHC is included. We compare their competitiveness with the EW and Higgs data in terms of their exclusion potential. This contribution to the Snowmass procedure contains preliminary results of [1] and serves as a guideline for which regions in parameter space of Little Higgs models are still compatible for the upcoming LHC runs and future experiments at the energy frontier. For this purpose we propose two different benchmark scenarios for the Littlest Higgs with T-parity, one with heavy mirror quarks, one with light ones.

We revisit mass determination techniques for the minimum symmetric event topology, namely X pair production followed by X → N , where X and N are unknown particles with the masses to be measured, and N is an invisible particle, concentrating on the case where X is pair produced from a resonance. We consider separate scenarios, with different initial constraints on the invisible particle momenta, and present a systematic method to identify the kinematically allowed mass regions in the (m N , m X ) plane. These allowed regions exhibit a cusp structure at the true mass point, which is equivalent to the one observed in the m T 2 endpoints in certain cases. By considering the boundary of the allowed mass region we systematically define kinematical variables which can be used in measuring the unknown masses, and find a new expression for the m T 2 variable as well as its inverse. We explicitly apply our method to the case that X is pair produced from a resonance, and as a case study, we consider the process pp → A →χ + 1χ − 1 , followed bỹ χ ± 1 → ±ν , in the Minimal Supersymmetric Standard Model and show that our method provides a precise measurement of the chargino and sneutrino masses, m X and m N , at 14 TeV LHC with 300 fb −1 luminosity.