Kaluza-Klein gluons as a diagnostic of warped models

Abstract

We study the properties of ${g}^{1}$, the first excited state of the gluon in representative variants of the Randall-Sundrum (RS) model with the standard model (SM) fields in the bulk. We find that measurements of the coupling to light quarks (from the inclusive cross section for $pp\ensuremath{\rightarrow}{g}^{1}\ensuremath{\rightarrow}t\overline{t}$), the coupling to bottom quarks (from the rate of $pp\ensuremath{\rightarrow}{g}^{1}b$), as well as the overall width can provide powerful discriminants between the models. In models with large brane kinetic terms, the ${g}^{1}$ resonance can even potentially be discovered decaying into dijets against the large QCD background. We also derive bounds based on existing Tevatron searches for resonant $t\overline{t}$ production and find that they require ${M}_{{g}^{1}}\ensuremath{\gtrsim}950\text{ }\text{ }\mathrm{GeV}$. In addition, we explore the pattern of interference between the ${g}^{1}$ signal and the nonresonant SM background, defining an asymmetry parameter for the invariant mass distribution. The interference probes the relative signs of the couplings of the ${g}^{1}$ to light quark pairs and to $t\overline{t}$, and thus provides an indication that the top is localized on the other side of the extra dimension from the light quarks, as is typical in the RS framework.