Little composite dark matter

Abstract

We examine the dark matter phenomenology of a composite electroweak singlet state. This singlet belongs to the Goldstone sector of a well-motivated extension of the Littlest Higgs with T-parity. A viable parameter space, consistent with the observed dark matter relic abundance as well as with the various collider, electroweak precision and dark matter direct detection experimental constraints is found for this scenario. T-parity implies a rich LHC phenomenology, which forms an interesting interplay between conventional natural SUSY type of signals involving third generation quarks and missing energy, from stop-like particle production and decay, and composite Higgs type of signals involving third generation quarks associated with Higgs and electroweak gauge boson, from vector-like top-partners production and decay. The composite features of the dark matter phenomenology allows the composite singlet to produce the correct relic abundance while interacting weakly with the Higgs via the usual Higgs portal coupling [Formula: see text], thus evading direct detection.

Fig. 1

Left panel : Numeric results for branching ratios of $T^{+}$ for $f=1$ TeV. Right Panel: Numeric results for branching ratios of $T^{-}$ for $f=1$ TeV, $r=3$ and $m_s=200$ GeV. The mass of $B_H$ is a function of f, r, in this case $m_{B_H}=270$GeV

Fig. 2

Numeric results for the branching ratios of the upper (lower) component of ${\psi }_{-}$ presented in the left (right) panel, with $f=1\text{TeV},r=3,m_s=200\text{GeV},m_{\phi }=1\text{TeV}$ and ${\lambda }_2=2.5$. The masses of the heavy gauge boson are fixed at $m_{B_H}=270$ GeV and $m_{W_H}=2.1$ TeV. The dashed colored lines indicate the branching ratios to the different exclusive final states. The solid thick lines indicate the sum of branching ratios with either a top (purple curve) or a bottom (yellow curve) at the final state

Fig. 3

Left Panel: Exclusion limits (blue region) in the $(m_{{\psi }^{-}},m_{T^{-}})$ plane, using recasted limits from the CMS SUSY search of Ref. [42]. We impose the condition of Eqs. (90) and (90), assuming branching ratios of 100%. Right Panel: Exclusion limits in the $(f,{\lambda }_2)$ plane using Ref. [42] (blue region, using the bound from Eq. (92)), Ref. [38] (orange region) and Ref. [39] (green region)

Fig. 4

Combined EWPT and LHC exclusion regions in the $(f,{\lambda }_2)$ plane, for $r=3$ and $\mathrm{\Lambda }=4\pi f$. The EWPT exclusion regions due to T-parameter (blue region) and $\delta g_L^{Z\overline{b}b}$ (orange region) are plotted at the $3\sigma$ level using the results of Ref. [45], $T=0.12\pm 0.07$ and $\delta g_L^{b\overline{b}}=0.002\pm 0.001$. The LHC exclusion (green region) is due to Ref. [42] using the lower bound of Eq. (92)

Fig. 5

Left panel: The thermally averaged cross section as a function of the DM mass $m_s$ for ${\lambda }_{\text{DM}}=0.07,f=1000\text{GeV},r=3$ and ${\lambda }_2=3$. The dashed line at $⟨\sigma v⟩=1$ pb represents the cross section that produces the correct relic abundance according to Eq. (107). Right panel: The thermally averaged cross section as a function of ${\lambda }_{\text{DM}}$ for different values of $m_s$ with $f=1000\text{GeV},r=3$ and ${\lambda }_2=3$. The dashed line at $⟨\sigma v⟩=1$ pb represents the cross section that produces the correct relic abundance according to Eq. (107)

Fig. 6

Singlet relic abundance in the $m_s,{\lambda }_{\text{DM}}$ plane for $f=1$ TeV (left), $f=1.2$ TeV (middle) and $f=1.4$ TeV (right), for fixed $r=3$ and minimal ${\lambda }_2\sim \frac{2300\text{GeV}}{f}$. The solid blue lines represent areas where ${\mathrm{\Omega }}_s={\mathrm{\Omega }}_{\text{DM}}$. The blue areas are regions where ${\mathrm{\Omega }}_s>{\mathrm{\Omega }}_{\text{DM}}$, and therefore are excluded. The grey regions are excluded by XENON1T [59] after 34.2 live days. The Dashed lines are the projected sensitivities for XENON1T at $1.1\text{yrs}\times \mathrm{Ton}$[60]

Fig. 7

The effects of changing r and ${\lambda }_2$ on the relic abundance curves, shown as solid curves. The dashed curves represent the XENON1T [59] bounds after 34.2 live days. Increasing r has similar effects to lowering f - the coefficients of the non-renormalizable terms increase and their effect is noticeable at lower DM masses. Increasing ${\lambda }_2$ reduces the size of the coefficient of the dimension 5 contact term, therefore increasing $m_s^{\text{max}}=\sqrt{x_{\text{max}}}f$