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2.2.3 Contact InteractionsContact interactions are a generic framework describing the effects of hypothesizedparticles with an energy larger than the TeV scale, analogous to the Fermi currentcurrentdescription of the weak interaction. Predicted effects include shifts in thehigh-energy part of the dimuon spectrum and changes to the geometric distributionof dijet events.2.2.4 Alternative Electroweak Symmetry BreakingTechnicolorTechnicolor models provide an alternative mechanism of electroweak symmetry breakingby invoking a new QCD-like interaction that provides dynamical masses for electroweakgauge bosons and fermions. These models predict “technimesons” (the spinzeroπ TC and spin-one ρ TC , a TC and ω TC ), condensates of the fundamental particleswith TeV-scale masses, which should be detectable as resonances. The best modes fordiscovery at the LHC are expected to be ρ TC → WZ → 3lν, a TC → γW → lνγ andω TC → γZ → llγ decays, which are fully leptonic and thus benefit from reduced QCDbackground and better mass resolution.Little Higgs“Little Higgs” models propose a solution to the hierarchy problem of the StandardModel by proposing new TeV-scale particle to cancel the quadratically divergent Higgsmass corrections at one-loop order only. The resulting effective theory is then validonly up to about 10 TeV only, but does not require distasteful fine-tuning. Thepredicted particle spectrum depends on the detailed realization of these cancellations.In the “Littlest Higgs” model, for example, these additional particles are heavy copiesof the electroweak gauge bosons and heavy quarks as well as three scalar electroweakparticles with charges 2, 1 and 0. Detection of the doubly charged boson as well asthe heavy gauge bosons and top quarks has been studied.2.2.5 Same-Sign Top PairsIn the Standard Model, there is no mechanism for exclusive production of same-signtop quark pairs from hadron collisions. While processes that produce same-sign toppairs inclusively certainly exist, they contain a multitude of weak interaction verticesand thus have negligible cross sections. The detection of same-sign top pairs wouldtherefore be a strong indication of new physics. One of the candidate explanationswould be the existence of flavor changing neutral currents.Detection of such events can follow the lines of the search for ordinary leptonic toppair searches with a simple change of sign requirements.15