Taking a phenomenological approach, we study a color sextet scalar at the LHC. We focus on the QCD production of a color sextet pair Φ_6Φ̅_6 through gg fusion and qq̅ annihilation. Its unique coupling to ψ̅^̅c̅ψ allows the color sextet scalar to decay into same-sign diquark states, such as Φ_6→ tt/tt^*. We propose a new reconstruction in the multijet plus same sign dilepton with missing transverse energy samples to search for on-shell ttt̅t̅ final states from sextet scalar pair production.

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... s to the large QCD production, the search covers the sextet mass range up to 1 TeV for 100 fb^-1 integrated luminosity.