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LHC Signals from Warped Extra Dimensions

Kaustubh Agashe, Alexander Belyaev, Tadas Krupovnickas, Gilad Perez, Joseph Virzi

TL;DR

This paper investigates the LHC phenomenology of Kaluza-Klein gluons in a warped extra-dimension model with bulk Standard Model fields. It shows that KK gluon production is suppressed and the particle is broad due to dominant decays to top quarks, yet a discovery is possible for masses up to ~4 TeV with 100 fb⁻¹ by combining differential tt̄ cross sections with a large left-right top polarization asymmetry and using highly energetic top-jet strategies. The study also discusses the electroweak KK sector, potential effects from enhanced bL couplings, and the broader implications for other UV-complete strong dynamics scenarios. Overall, it provides concrete search strategies for heavy, broad resonances with non-universal couplings that favor third-generation final states in TeV-scale holographic frameworks.

Abstract

We study production of Kaluza-Klein gluons (KKG) at the Large Hadron Collider (LHC) in the framework of a warped extra dimension with the Standard Model (SM) fields propagating in the bulk. We show that the detection of KK gluon is challenging since its production is suppressed by small couplings to the proton's constituents. Moreover, the KK gluon decays mostly to top pairs due to an enhanced coupling and hence is broad. Nevertheless, we demonstrate that for m_{KKG} \lesssim 4 TeV, 100 fb^{-1} of data at the LHC can provide discovery of the KK gluon. We utilize a sizeable left-right polarization asymmetry from the KK gluon resonance to maximize the signal significance, and we explore the novel feature of extremely highly energetic "top-jets". We briefly discuss how the detection of electroweak gauge KK states (Z/W) faces a similar challenge since their leptonic decays (``golden'' modes) are suppressed. Our analysis suggests that other frameworks, for example little Higgs, which rely on UV completion via strong dynamics might face similar challenges, namely (1) Suppressed production rates for the new particles (such as Z'), due to their ``light-fermion-phobic'' nature, and (2) Difficulties in detection since the new particles are broad and decay predominantly to third generation quarks and longitudinal gauge bosons.

LHC Signals from Warped Extra Dimensions

TL;DR

This paper investigates the LHC phenomenology of Kaluza-Klein gluons in a warped extra-dimension model with bulk Standard Model fields. It shows that KK gluon production is suppressed and the particle is broad due to dominant decays to top quarks, yet a discovery is possible for masses up to ~4 TeV with 100 fb⁻¹ by combining differential tt̄ cross sections with a large left-right top polarization asymmetry and using highly energetic top-jet strategies. The study also discusses the electroweak KK sector, potential effects from enhanced bL couplings, and the broader implications for other UV-complete strong dynamics scenarios. Overall, it provides concrete search strategies for heavy, broad resonances with non-universal couplings that favor third-generation final states in TeV-scale holographic frameworks.

Abstract

We study production of Kaluza-Klein gluons (KKG) at the Large Hadron Collider (LHC) in the framework of a warped extra dimension with the Standard Model (SM) fields propagating in the bulk. We show that the detection of KK gluon is challenging since its production is suppressed by small couplings to the proton's constituents. Moreover, the KK gluon decays mostly to top pairs due to an enhanced coupling and hence is broad. Nevertheless, we demonstrate that for m_{KKG} \lesssim 4 TeV, 100 fb^{-1} of data at the LHC can provide discovery of the KK gluon. We utilize a sizeable left-right polarization asymmetry from the KK gluon resonance to maximize the signal significance, and we explore the novel feature of extremely highly energetic "top-jets". We briefly discuss how the detection of electroweak gauge KK states (Z/W) faces a similar challenge since their leptonic decays (``golden'' modes) are suppressed. Our analysis suggests that other frameworks, for example little Higgs, which rely on UV completion via strong dynamics might face similar challenges, namely (1) Suppressed production rates for the new particles (such as Z'), due to their ``light-fermion-phobic'' nature, and (2) Difficulties in detection since the new particles are broad and decay predominantly to third generation quarks and longitudinal gauge bosons.

Paper Structure

This paper contains 11 sections, 5 equations, 6 figures, 1 table.

Table of Contents

  1. Introduction
  2. LHC signals
  3. KK gluons
  4. Event Generation and Jet Reconstruction
  5. Details of analysis
  6. Differential cross section
  7. Polarization asymmetry
  8. Signal versus background optimization
  9. Electroweak sector & alternative quark configuration
  10. Effects of enhanced $b_L$ coupling to KK gluon
  11. Conclusions

Figures (6)

  • Figure 1: The total cross section of KK gluon production at the LHC as a function of its mass ($M_{KKG}$).
  • Figure 2: The branching ratios of the KK gluon as a function of its mass.
  • Figure 3: The total decay width of KK gluon as a function of its mass
  • Figure 4: Invariant $t\bar{t}$ mass distribution for $M_{KKG} = 3\,$TeV production at the LHC. The solid curve presents signal+background distribution, while the dashed curve presents the $t\bar{t}$ SM background, based on partonic level analysis.
  • Figure 5: Invariant $t\bar{t}$ mass distribution for 3 TeV KKG, focusing on the area near the peak. The error bars correspond to statistical uncertainties and represent our particle level analysis. The dotted line stands for the SM prediction. The dashed-dotted line shows the $Wjj$ background. The dashed line shows the signal+background from Sherpa's partonic level analysis.
  • ...and 1 more figures