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Experimental Probes of Localized Gravity: On and Off the Wall

H. Davoudiasl, J. L. Hewett, T. G. Rizzo

TL;DR

The paper analyzes the Randall-Sundrum model of localized gravity under two scenarios: Standard Model fields on the TeV-brane or propagating in the RS bulk. It derives the KK spectra and couplings for gravitons, bulk gauge fields, and bulk fermions, highlighting how the 5D fermion mass parameter ν qualitatively changes collider and precision-electroweak signatures. In the bulk-SM case, a rich ν-dependent phenomenology emerges with distinct regions where direct and indirect searches have varying reach, while in the TeV-brane case, gravitons and KK gauge states can be probed at the LHC, and electroweak symmetry breaking is shown to occur on the TeV-brane. The study demonstrates the complementary constraints from precision EW data and collider searches, constraining the RS parameter space and guiding experimental tests of localized gravity at the TeV scale.

Abstract

The phenomenology of the Randall-Sundrum model of localized gravity is analyzed in detail for the two scenarios where the Standard Model (SM) gauge and matter fields are either confined to a TeV scale 3-brane or may propagate in a slice of five dimensional anti-deSitter space. In the latter instance, we derive the interactions of the graviton, gauge, and fermion Kaluza-Klein (KK) states. The resulting phenomenological signatures are shown to be highly dependent on the value of the 5-dimensional fermion mass and differ substantially from the case where the SM fields lie on the TeV-brane. In both scenarios, we examine the collider signatures for direct production of the graviton and gauge KK towers as well as their induced contributions to precision electroweak observables. These direct and indirect signatures are found to play a complementary role in the exploration of the model parameter space. In the case where the SM field content resides on the TeV-brane, we show that the LHC can probe the full parameter space and hence will either discover or exclude this model if the scale of electroweak physics on the 3-brane is less than 10 TeV. We also show that spontaneous electroweak symmetry breaking of the SM must take place on the TeV-brane.

Experimental Probes of Localized Gravity: On and Off the Wall

TL;DR

The paper analyzes the Randall-Sundrum model of localized gravity under two scenarios: Standard Model fields on the TeV-brane or propagating in the RS bulk. It derives the KK spectra and couplings for gravitons, bulk gauge fields, and bulk fermions, highlighting how the 5D fermion mass parameter ν qualitatively changes collider and precision-electroweak signatures. In the bulk-SM case, a rich ν-dependent phenomenology emerges with distinct regions where direct and indirect searches have varying reach, while in the TeV-brane case, gravitons and KK gauge states can be probed at the LHC, and electroweak symmetry breaking is shown to occur on the TeV-brane. The study demonstrates the complementary constraints from precision EW data and collider searches, constraining the RS parameter space and guiding experimental tests of localized gravity at the TeV scale.

Abstract

The phenomenology of the Randall-Sundrum model of localized gravity is analyzed in detail for the two scenarios where the Standard Model (SM) gauge and matter fields are either confined to a TeV scale 3-brane or may propagate in a slice of five dimensional anti-deSitter space. In the latter instance, we derive the interactions of the graviton, gauge, and fermion Kaluza-Klein (KK) states. The resulting phenomenological signatures are shown to be highly dependent on the value of the 5-dimensional fermion mass and differ substantially from the case where the SM fields lie on the TeV-brane. In both scenarios, we examine the collider signatures for direct production of the graviton and gauge KK towers as well as their induced contributions to precision electroweak observables. These direct and indirect signatures are found to play a complementary role in the exploration of the model parameter space. In the case where the SM field content resides on the TeV-brane, we show that the LHC can probe the full parameter space and hence will either discover or exclude this model if the scale of electroweak physics on the 3-brane is less than 10 TeV. We also show that spontaneous electroweak symmetry breaking of the SM must take place on the TeV-brane.

Paper Structure

This paper contains 5 sections, 38 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Peeling the Standard Model off the Wall
  3. Gravitons and Bulk Gauge Fields
  4. Bulk Fermion Fields
  5. Couplings of the KK Modes

Figures (3)

  • Figure 1: Relative mass spectra in units of $ke^{-kr_c\pi}$ of the KK excitations of the fermion fields as a function of their bulk mass parameter $\nu$, as well as for the graviton and the gauge boson fields as described in the text.
  • Figure 2: The coupling strength of the zero-mode fermions to the first five KK gauge boson states in units of the corresponding SM coupling strength as a function of $\nu$. From top to bottom on the right-hand side of the figure the curves are for the first, third, fifth, fourth and second gauge KK excitations.
  • Figure 3: The coupling strength of the zero-mode fermions to the first five KK graviton states in units of $\Lambda_\pi^{-1}$ as a function of $\nu$. From top to bottom on the right-hand side of the figure the curves are for the first, third, fifth, fourth and second graviton KK levels.