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Improved Bounds on Universal Extra Dimensions and Consequences for LKP Dark Matter

Thomas Flacke, Dan Hooper, John March-Russell

TL;DR

The paper strengthens the lower bound on the UED compactification scale by performing a comprehensive EWPO analysis that includes $2$-loop SM Higgs contributions and the extended LEP1/LEP2 observable set, yielding $M_c = R^{-1} > 700$ GeV at 99% CL (and $> 800$ GeV at 95% CL). This tighter constraint arises from the breakdown of the heavy-Higgs cancellation when two-loop effects are included and from the additional LEP2 constraints on the oblique parameters $X,Y,W$. The updated bound significantly narrows the viable parameter space for KK dark matter, shifting the expected LKP mass range higher and altering the prospects for direct and indirect detection, with implications for experiments like AMS-02 and IceCube. Overall, the work demonstrates the power of precision EW measurements, including higher-order SM corrections, to constrain extra-dimensional theories and their DM phenomenology.

Abstract

We study constraints on models with a flat "Universal'' Extra Dimension in which all Standard Model fields propagate in the bulk. A significantly improved constraint on the compactification scale is obtained from the extended set of electroweak precision observables accurately measured at LEP1 and LEP2. We find a lower bound of M_c = R^{-1} > 700 (800) GeV at the 99% (95%) confidence level. We also discuss the implications of this constraint on the prospects for the direct and indirect detection of Kaluza-Klein dark matter in this model.

Improved Bounds on Universal Extra Dimensions and Consequences for LKP Dark Matter

TL;DR

The paper strengthens the lower bound on the UED compactification scale by performing a comprehensive EWPO analysis that includes -loop SM Higgs contributions and the extended LEP1/LEP2 observable set, yielding GeV at 99% CL (and GeV at 95% CL). This tighter constraint arises from the breakdown of the heavy-Higgs cancellation when two-loop effects are included and from the additional LEP2 constraints on the oblique parameters . The updated bound significantly narrows the viable parameter space for KK dark matter, shifting the expected LKP mass range higher and altering the prospects for direct and indirect detection, with implications for experiments like AMS-02 and IceCube. Overall, the work demonstrates the power of precision EW measurements, including higher-order SM corrections, to constrain extra-dimensional theories and their DM phenomenology.

Abstract

We study constraints on models with a flat "Universal'' Extra Dimension in which all Standard Model fields propagate in the bulk. A significantly improved constraint on the compactification scale is obtained from the extended set of electroweak precision observables accurately measured at LEP1 and LEP2. We find a lower bound of M_c = R^{-1} > 700 (800) GeV at the 99% (95%) confidence level. We also discuss the implications of this constraint on the prospects for the direct and indirect detection of Kaluza-Klein dark matter in this model.

Paper Structure

This paper contains 8 sections, 21 equations, 3 figures.

Table of Contents

  1. Introduction
  2. The UED Model
  3. Constraints from Precision Measurements at LEP1 and LEP2
  4. Constraints on UED Models from EWPO
  5. KK Dark Matter
  6. Conclusions
  7. Acknowledgements
  8. NDA for Universal Extra Dimensions

Figures (3)

  • Figure 1: Comparison of the 2-loop order Higgs-dependent contributions to the electroweak gauge boson radiative corrections as implemented in the TopaZ0 code (solid lines) with the simple numerical interpolations (dashed lines) given in Eq.(\ref{['SMepsilon']}).
  • Figure 2: The contribution to $\hat{T}$ from the first three KK levels (dashed lines) for $M_c=400$ GeV as a function of Higgs mass in the range 100 to 800 GeV, as well as the sum over the first 10 KK modes (solid line) and the numerically-interpolated Higgs-dependent correction (dotted line) arising from $\epsilon_{1,SM}$.
  • Figure 3: The 95% (dashed line) and 99% (dotted line) confidence limit exclusion zones for the UED model, as a function of Higgs mass in the range 115 GeV to 400 GeV, and mass $M_1=1/R$ of the lightest KK excitation in the range 500 GeV to 1 TeV. The excluded regions are towards the bottom right of the figure.