Many Standard Model extensions can contribute to four-lepton signals at large colliders. We review the particular case of leptophilic interactions eventually observable at the LHC and the ILC, paying special attention to the addition of a new vector
boson coupled to muon minus tau lepton number, $Z_{mu - tau}$, and emphasizing the prospects at a very large hadron collider with $sqrt s =$ 100 TeV. We also discuss in this case the new contribution to two-lepton (Drell-Yan) production when the new leptophilic interaction has a non-vanishing kinetic mixing with the SM.
The Large Hadron Collider can do precision physics at a level that is competitive with electroweak precision constraints when probing physics beyond the Standard Model. We present a simple yet general parameterization of the effect of an arbitrary nu
mber of lepton-quark contact interactions on any di-lepton observable at hadron colliders. This parameterization can be easily adopted by the experimental collaborations to put bounds on arbitrary combinations of lepton-quark contact interactions. We compute the corresponding bounds from current di-lepton resonance searches at the LHC and find that they are competitive with and often complementary to indirect constraints from electroweak precision data. We combine all current constraints in a global analysis to obtain the most stringent bounds on lepton-quark contact interactions. We also show that the high-energy phase of the LHC has a unique potential in terms of discovery and discrimination power among different types of lepton-quark contact interactions.
We show that a discrete exchange symmetry can give rise to realistic dark matter candidates in models with warped extra dimensions. We show how to realize our construction in a variety of models with warped extra dimensions and study in detail a real
istic model of Gauge-Higgs Unification/composite Higgs in which the observed amount of dark matter is naturally reproduced. In this model, a realistic pattern of electroweak symmetry breaking typically occurs in a region of parameter space in which the fit to the electroweak precision observables improves, the Higgs is heavier than the experimental bound and new light quark resonances are predicted. We also quantify the fine-tuning of such scenarios, and discuss in which sense Gauge-Higgs Unification models result in a natural theory of electroweak symmetry breaking.
