Dark Matter and Electroweak Symmetry Breaking in Models with Warped Extra Dimensions

TL;DR

The paper introduces a discrete ${\bf Z}_2$ exchange symmetry in warped extra dimensions to generate realistic dark matter candidates without new parameters, exemplified in Gauge-Higgs Unification models where the dark sector cooperates with electroweak symmetry breaking. By doubling a subset of fields, the authors obtain a lightest ${\bf Z}_2$-odd particle $X_-$ (a sub-TeV spin-1 state) whose relic density can match observations, especially when coannihilations with near-degenerate ${\bf Z}_2$-odd fermions are considered. They demonstrate that viable EWSB patterns and EW precision constraints align with the regions yielding the correct dark matter abundance, and they explore non-perturbative corrections (bound states, Sommerfeld effects) which turn out to be subdominant. The construction extends naturally to other warped models (RS with bulk fields and Higgsless scenarios), predicting distinctive collider signatures such as jets plus missing energy from near-degenerate spectra of ${\bf Z}_2$-odd states, while direct detection remains challenging due to suppressed couplings to light quarks. Overall, the work ties dark matter viability to the dynamics of EWSB in warped spaces, offering testable collider phenomenology and a minimal DM realization in these theories.

Abstract

We show that a discrete exchange symmetry can give rise to realistic dark matter candidates in models with warped extra dimensions. We show how to realize our construction in a variety of models with warped extra dimensions and study in detail a realistic model of Gauge-Higgs Unification/composite Higgs in which the observed amount of dark matter is naturally reproduced. In this model, a realistic pattern of electroweak symmetry breaking typically occurs in a region of parameter space in which the fit to the electroweak precision observables improves, the Higgs is heavier than the experimental bound and new light quark resonances are predicted. We also quantify the fine-tuning of such scenarios, and discuss in which sense Gauge-Higgs Unification models result in a natural theory of electroweak symmetry breaking.

Figures (3)

• Figure 1: Projection onto the $c_{u}$-$c_{q_{1}}$ plane for the two phenomenologically viable regions. The darker areas marked $s_{h} = 0$ correspond to no EWSB. We plot $s_{h}$ averaged over the rest of the parameters, which increases as the gray bands become lighter (see text). The green dots satisfy $145~{\rm GeV} < m_{t}(\mu \sim \mu_{IR}) < 155~{\rm GeV}$. The red triangles mark the points consistent with the WMAP constraint, Eq. (\ref{['WMAP']}), at the $2\sigma$ level. The blue stars correspond to a sample of points that are consistent with EW precision data at the $99\%$ CL, and the Higgs LEP bound.
• Figure 2: Masses of the DM candidate, $X_{-}$, and the Higgs for points (red dots) that reproduce the top mass and the WMAP constraint, Eq. (\ref{['WMAP']}), for the $c_{u} < 0$ region (left panel) and $c_{u} > 0$ region (right panel). The blue stars correspond to the subset of points that also obey the EW precision constraints at the $99\%$ CL, and the LEP bound on the Higgs mass, which is also indicated by the dashed horizontal line. The light bands indicate the approximate bounds from the Tevatron on the colored vector-like quarks, that have mass close to $m_{X_{-}}$, taking into account the different multiplicities for positive and negative $c_u$.
• Figure 3: Left panel: logarithmic sensitivity as a function of $s_{h}$. Right panel: logarithmic sensitivity with the requirement that the top mass be kept fixed (see text). The green dots correspond to a random scan over parameter space with $c_{u} > 0$. The subset that satisfies $140~{\rm GeV} < m_{t}(\mu \sim \mu_{IR}) < 160~{\rm GeV}$ is indicated by red triangles. The results for the $c_{u} < 0$ region are similar.