The Color Discriminant Variable and Scalar Diquarks at the LHC

Abstract: The LHC is actively searching for narrow dijet resonances corresponding to physics beyond the Standard Model. Among the many resonances that have been postulated (e.g., colored vectors, scalars, and fermions) one that would have a particularly large production rate at the LHC would be a scalar diquark produced in the s-channel via fusion of two valence quarks. In previous work, we introduced a color discriminant variable that distinguishes among various dijet resonances, drawing on measurements of the dijet resonance mass, total decay width and production cross-section. Here, we show that this model-independent method applies well to color-triplet and color-sextet scalar diquarks, distinguishing them clearly from other candidate resonances. We also introduce a more transparent theoretical formulation of the color discriminant variable that highlights its relationship to the branching ratios of the resonance into incoming and outgoing partons and to the properties of those partons. While the original description of the color discriminant variable remains convenient for phenomenological use upon discovery of a new resonance, the new formulation makes it easier to predict the value of the variable for a given class of resonance.