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Looking For TeV-Scale Strings and Extra-Dimensions

E. Accomando, I. Antoniadis, K. Benakli

TL;DR

This paper analyzes how Type I brane-world setups with TeV-scale extra dimensions modify collider phenomenology, focusing on how gauge factors propagate on branes and which KK excitations or stringy effects arise. It identifies five principal models, labeled $(l,l,l)$, $(t,l,l)$, $(t,l,t)$, $(t,t,l)$, and $(t,t,t)$, and derives the corresponding signatures at the LHC, including resonances and indirect effects from KK exchanges. The study finds that direct KK resonances are visible only for $R^{-1} \lesssim 6\,$TeV, while indirect effects extend reach up to $R^{-1} \sim 20\,$TeV for gluons and $8$--$15\,$TeV for electroweak bosons; in the case where no gauge boson propagates in the extra dimension, tree-level exchange of massive open-string oscillation modes dominates over graviton KK exchange, enabling bounds on the string scale. These results map out the LHC discovery potential and emphasize how brane-localization patterns constrain experimental probes of TeV-scale strings and extra dimensions.

Abstract

In contrast to the old heterotic string case, the (weakly coupled) type I brane framework allows to have all, part or none of the standard model gauge group factors propagating in large extra--dimensions of TeV$^{-1}$ size. We investigate the main experimental signatures of these possibilities, related to the production of Kaluza-Klein excitations of gluons and electroweak gauge bosons. A discovery through direct observation of resonances is possible only for compactification scales below 6 TeV. However effects due to exchange of virtual Kaluza-Klein excitations could be observed for higher scales. We find that LHC can probe compactification scales as high as 20 TeV for excitations of gluons and 8-15 TeV for excitations of electroweak gauge bosons. Finally, in the case where no gauge boson feels the extra-dimension, we find that effective contact interactions due to massive string mode oscillations dominate those due to the exchange of Kaluza-Klein excitations of gravitons and could be used to obtain bounds on the string scale.

Looking For TeV-Scale Strings and Extra-Dimensions

TL;DR

This paper analyzes how Type I brane-world setups with TeV-scale extra dimensions modify collider phenomenology, focusing on how gauge factors propagate on branes and which KK excitations or stringy effects arise. It identifies five principal models, labeled , , , , and , and derives the corresponding signatures at the LHC, including resonances and indirect effects from KK exchanges. The study finds that direct KK resonances are visible only for TeV, while indirect effects extend reach up to TeV for gluons and --TeV for electroweak bosons; in the case where no gauge boson propagates in the extra dimension, tree-level exchange of massive open-string oscillation modes dominates over graviton KK exchange, enabling bounds on the string scale. These results map out the LHC discovery potential and emphasize how brane-localization patterns constrain experimental probes of TeV-scale strings and extra dimensions.

Abstract

In contrast to the old heterotic string case, the (weakly coupled) type I brane framework allows to have all, part or none of the standard model gauge group factors propagating in large extra--dimensions of TeV size. We investigate the main experimental signatures of these possibilities, related to the production of Kaluza-Klein excitations of gluons and electroweak gauge bosons. A discovery through direct observation of resonances is possible only for compactification scales below 6 TeV. However effects due to exchange of virtual Kaluza-Klein excitations could be observed for higher scales. We find that LHC can probe compactification scales as high as 20 TeV for excitations of gluons and 8-15 TeV for excitations of electroweak gauge bosons. Finally, in the case where no gauge boson feels the extra-dimension, we find that effective contact interactions due to massive string mode oscillations dominate those due to the exchange of Kaluza-Klein excitations of gravitons and could be used to obtain bounds on the string scale.

Paper Structure

This paper contains 6 sections, 8 equations, 6 figures.

Table of Contents

  1. Introduction
  2. Bulk and boundary states within the brane picture
  3. The "standard" $(l,l,l)$ scenario:
  4. The cases $(t,l,l)$, $(t,l,t)$ and $(t,t,l)$:
  5. Limit on the string scale:
  6. Conclusions

Figures (6)

  • Figure 1: First resonances in the LHC experiment due to a KK excitation of gluon for one extra-dimension at 4 and 5 TeV.
  • Figure 2: Number of standard deviation in number of observerd dijets from the expected standard model value, due to the presence of a TeV-scale extra-dimension of compactification radius $R$.
  • Figure 3: First resonances in the LHC experiment due to a KK excitation of $W_{\pm}^{(n)}$ for one extra-dimension at 4, 5 and 6 TeV. We plot the differential cross section as function of the transverse mass for the $W$s.
  • Figure 4: First resonances in the LHC experiment due to a KK excitation of photon and Z for one extra-dimension at 4 TeV. From highest to lowest: excitation of photon+Z, photon and Z boson.
  • Figure 5: Number of standard deviation in the number of $l^+ l^-$ pairs and $\nu_l l$ pairs produced from the expected standard model value due to the presence of one extra-dimension of radius $R$.
  • ...and 1 more figures