Dark Majorana Particles from the Minimal Walking Technicolor

TL;DR

The paper investigates a dark matter candidate from minimal walking technicolor where techniquarks and technigluons in the adjoint representation form a colorless bound state that can acquire a Majorana mass via technibaryon-number violation. Through a seesaw-like mechanism, two Majorana states $N_1,N_2$ arise, with the lighter $N_2$ acting as the DM candidate protected by a $Z_2$ symmetry; relic density is computed from a $Z$-mediated annihilation cross section in two mass regimes, yielding $oxed{\,oxed{ ho_{N_2} h^2 \,}igr|_{ ext{DM}} \, \approx \, 0.112}$ for appropriate mixing angle and $m$. LEP constraints on additional neutrals and the suppression of direct detection rates due to Majorana nature mean the model can evade current CDMS bounds while predicting suppressed but testable signals in future experiments. The work offers a complementary DM scenario to prior technicolor models and motivates lattice studies of bound states in higher-representation gauge theories.

Abstract

We investigate the possibility of a dark matter candidate emerging from a minimal walking technicolor theory. In this case techniquarks as well as technigluons transform under the adjoint representation of SU(2) of technicolor. It is therefore possible to have technicolor neutral bound states between a techniquark and a technigluon. We investigate this scenario by assuming that such a particle can have a Majorana mass and we calculate the relic density. We identify the parameter space where such an object can account for the full dark matter density avoiding constraints imposed by the CDMS and the LEP experiments.

Figures (3)

• Figure 1: The solid line shows the dependence of $\sin\theta$ on the mass of $N_2$ (in GeV), in order the relic density $\Omega_{N_2}h^2=0.112$. The dashed line shows the constraint on $m$ and $\sin\theta$ imposed by LEP. The area above the dashed line is excluded. This means that $m$ should be larger than 23 GeV, which is the value where the two curves cross each other.
• Figure 2: As in Fig. 1 the solid line shows the dependence of $\sin\theta$ on the mass of $N_2$ (in GeV), in order the relic density $\Omega_{N_2}h^2=0.112$.
• Figure 3: Left Panel:The required exposure of the Ge detectors in $\text{kg}\cdot\text{days}$ for a single count (with 90$\%$ confidence level) as a function of $m$ (in GeV) for the range $20<m<80$, although in reality $m$ is constrained by LEP to be larger than 23 GeV. The thin solid line corresponds to local dark matter density $\rho=0.4 ~\text{GeV}/\text{cm}^3$, the dashed one to $\rho=0.3 ~\text{GeV}/\text{cm}^3$ and the thick solid one to $\rho=0.2 ~\text{GeV}/\text{cm}^3$. For the purposes of presentation we show the required exposure up to 100000 $\text{kg}\cdot \text{days}$. Around the resonance, where $m=45.5$ GeV, the required exposure has a sharp peak of about $10^7$$\text{kg}\cdot \text{days}$. Right Panel:As in the left panel for $80<m<2000$ GeV.