Kaluza-Klein States of the Standard Model Gauge Bosons: Constraints From High Energy Experiments

TL;DR

This work analyzes how one extra dimension with SM gauge bosons in the bulk induces Kaluza-Klein excitations that mix with SM bosons and contribute via virtual exchanges to high-energy processes. The authors formulate a five-dimensional model, reduce it to an effective four-dimensional theory, and introduce the parameter $ $\eta = \frac{\pi^2}{3 M_C^2}$ to capture KK effects across observables. A global fit to LEP2, HERA, Tevatron, and related data yields no evidence for KK states and sets a 95% C.L. lower limit $M_C > 6.8$ TeV, surpassing pure precision-EW bounds. They also forecast Run 2 and LHC sensitivities, finding potential to probe $M_C$ well into the multi-TeV regime, with the LHC reaching beyond 10–15 TeV depending on systematic errors.

Abstract

In theories with the standard model gauge bosons propagating in inverse-TeV-size extra dimensions, their Kaluza-Klein states interact with the rest of the SM particles confined to the 3-brane. We look for possible signals for this interaction in the present high-energy collider data, and estimate the sensitivity offered by the next generation of collider experiments. Based on the present data from the LEP 2, Tevatron, and HERA experiments, we set a lower limit on the extra dimension compactification scale Mc > 6.8 TeV at the 95% confidence level (dominated by the LEP 2 results) and quote expected sensitivities in the Tevatron Run 2 and at the LHC.