Kaluza-Klein Gluons as a Diagnostic of Warped Models

TL;DR

This paper investigates the properties of the first excited gluon state in Randall-Sundrum models, proposing methods to distinguish models through measurements of couplings, widths, and interference effects, with implications for collider searches.

Contribution

It introduces a comprehensive analysis of the $g^{1}$ gluon resonance in warped models, including new discriminants based on couplings, widths, and interference patterns, and derives bounds from existing collider data.

Findings

$g^{1}$ can be discovered via dijet decays in certain models.

Existing Tevatron data requires $M_{g^{1}} \,\gtrsim\, 950$ GeV.

Interference patterns reveal the localization of quarks in the extra dimension.

Abstract

We study the properties of $g^{1}$, the first excited state of the gluon in representative variants of the Randall Sundrum model with the Standard Model fields in the bulk. We find that measurements of the coupling to light quarks (from the inclusive cross-section for $pp\to g^{1} \to t\bar t$), the coupling to bottom quarks (from the rate of $pp\to g^{1} b$), 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 $t \bar{t}$ production and find that they require $M_{g^{1}} \gtrsim 950$ GeV. In addition we explore the pattern of interference between the $g^1$ signal and the non-resonant 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 $t\bar t$, 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.