Naturality, unification, and dark matter

We consider a model where electroweak symmetry breaking is driven by technicolor dynamics with minimal particle content required for walking coupling and saturation of global anomalies. Furthermore, the model features three additional Weyl fermions singlet under technicolor interactions, two of which provide for a one-loop unification of the standard model gauge couplings. Among these extra matter fields exists a possible candidate for weakly interacting dark matter. We evaluate the relic densities and find that they are sufficient to explain the cosmological observations and avoid the experimental limits from earth-based searches. Hence, we establish a nonsupersymmetric framework where hierarchy and naturality problems are solved, coupling constant unification is achieved, and a plausible dark matter candidate exists.

Figure 1

Shown are the constant ${\Omega }_{{\chi }_2}$ contours as a function of WIMP mass and the mixing angle $\sin \theta$ with ${\rho }_{12}=-1$. Scenario I is shown by thick black dotted lines and scenario II by thick solid black and thin dotted lines. In the left picture Higgs-boson mass is 200 GeV and in the right picture 500 GeV. The area between the thick lines is favored by the WMAP results for dark matter density. The area to the left from the thick gray line in the left panel is excluded by the LEP limit $m_{w_D}<104.5\mathrm{GeV}$, assuming $m_1/m_2\equiv A\ge 2$. The gray dashed and dash-dotted lines shown the same limit assuming that $A=4$ and $A=1.5$, respectively. Similar lines on the right panel show these constraints assuming an improved limit $m_{w_D}<200\mathrm{GeV}$. The horizontal lines in light gray are the upper limits for the $\sin \theta$ coming from the requirement that $m_2<m_{w_D}$, where the thick solid, thin dashed, and thin dash-dotted lines again correspond to the cases $A=2$, 4, and 1.5, respectively.

Figure 2

Same as in Fig. 1 but for ${\rho }_{12}=+1$.

Figure 3

Shown are the constraints and model predictions for the spin-independent WIMP-nucleon cross section. The dark gray area is excluded by the first XENON100 (2009, Net 446.8 kg-d) results [41] and the light gray area is further excluded by the CDMS-II results [33]. In the left picture the model predictions were calculated with $m_H=200\mathrm{GeV}$ and in the right picture with $m_H=500\mathrm{GeV}$. The black solid lines correspond to ${\rho }_{12}=+1$ and the dashed lines to ${\rho }_{12}=-1$ in the mass scenario II. The thick dash-dotted lines correspond to the (SM-like) cross section of the mass scenario I. Finally, the gray dotted lines display the projected sensitivity of the full XENON100 (up), the upgraded XENON100 (middle), and the XENON1T (low) experiments [45]. We used the tools of Ref. 46 to produce all the projected future experimental XENON limits.