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Exploring Small Extra Dimensions at the Large Hadron Collider

B. C. Allanach, K. Odagiri, M. J. Palmer, M. A. Parker, A. Sabetfakhri, B. R. Webber

TL;DR

The paper evaluates the LHC's ability to discover and characterize TeV-scale graviton resonances predicted by warped extra-dimension models. It implements a spin-2 graviton in HERWIG, simulates production and decays across leptonic, bosonic, hadronic, and Higgs-pair channels, and assesses coupling measurements via σ×B and angular distributions for ATLAS-like detectors. Across a broad parameter space, it demonstrates that e^+e^− and γγ channels offer strong discovery and coupling-precision potential, while WW, ZZ, and dijet channels enable cross-checks of universality; Higgs-pair decays are unlikely to be informative. The study shows that, in a representative RS scenario, the graviton mass and the size of the extra dimension can be extracted with percent-level precision, highlighting the LHC’s capability to test warped extra dimensions and gravity at the TeV scale.

Abstract

Many models that include small extra space dimensions predict graviton states which are well separated in mass, and which can be detected as resonances in collider experiments. It has been shown that the ATLAS detector at the Large Hadron Collider can identify such narrow states up to a mass of 2080 GeV in the decay mode G->ee, using a conservative model. This work extends the study of the ee channel over the full accessible parameter space, and shows that the reach could extend as high as 3.5 TeV. It then discusses ways in which the expected universal coupling of the resonance can be confirmed using other decay modes. In particular, the mode G-> di-photons is shown to be measurable with good precision, which would provide powerful confirmation of the graviton hypothesis. The decays G-> mu mu, WW, ZZ and jet--jet are measurable over a more limited range of couplings and masses. Using information from mass and cross-section measurements, the underlying parameters can be extracted. In one test model, the size of the extra dimension can be determined to a precision in length of 7x10^-33 m.

Exploring Small Extra Dimensions at the Large Hadron Collider

TL;DR

The paper evaluates the LHC's ability to discover and characterize TeV-scale graviton resonances predicted by warped extra-dimension models. It implements a spin-2 graviton in HERWIG, simulates production and decays across leptonic, bosonic, hadronic, and Higgs-pair channels, and assesses coupling measurements via σ×B and angular distributions for ATLAS-like detectors. Across a broad parameter space, it demonstrates that e^+e^− and γγ channels offer strong discovery and coupling-precision potential, while WW, ZZ, and dijet channels enable cross-checks of universality; Higgs-pair decays are unlikely to be informative. The study shows that, in a representative RS scenario, the graviton mass and the size of the extra dimension can be extracted with percent-level precision, highlighting the LHC’s capability to test warped extra dimensions and gravity at the TeV scale.

Abstract

Many models that include small extra space dimensions predict graviton states which are well separated in mass, and which can be detected as resonances in collider experiments. It has been shown that the ATLAS detector at the Large Hadron Collider can identify such narrow states up to a mass of 2080 GeV in the decay mode G->ee, using a conservative model. This work extends the study of the ee channel over the full accessible parameter space, and shows that the reach could extend as high as 3.5 TeV. It then discusses ways in which the expected universal coupling of the resonance can be confirmed using other decay modes. In particular, the mode G-> di-photons is shown to be measurable with good precision, which would provide powerful confirmation of the graviton hypothesis. The decays G-> mu mu, WW, ZZ and jet--jet are measurable over a more limited range of couplings and masses. Using information from mass and cross-section measurements, the underlying parameters can be extracted. In one test model, the size of the extra dimension can be determined to a precision in length of 7x10^-33 m.

Paper Structure

This paper contains 18 sections, 3 equations.

Table of Contents

  1. Introduction
  2. The event generator
  3. Measurements of the graviton couplings
  4. Graviton decays to leptons
  5. $G\rightarrow e^+e^-$
  6. $G\rightarrow \mu^+\mu^-$
  7. $G\rightarrow \tau^+\tau^-$
  8. Decays to vector bosons
  9. $G\rightarrow \gamma\gamma$
  10. $G\rightarrow WW\rightarrow l\nu jj$
  11. $G\rightarrow ZZ\rightarrow lljj$
  12. Decays to hadronic final states
  13. Inclusive decays to 2 jets
  14. Decays to heavy quarks
  15. Decays to Higgs pairs
  16. ...and 3 more sections