Multicomponent dark matter systems and their observation prospects

Conversions and semiannihilations of dark matter (DM) particles in addition to the standard DM annihilations are considered in a three-component DM system. We find that the relic abundance of DM can be very sensitive to these nonstandard DM annihilation processes, which has been recently found for two-component DM systems. To consider a concrete model of a three-component DM system, we extend the radiative seesaw model of Ma by adding a Majorana fermion $\chi$ and a real scalar boson $\varphi$, to obtain a $Z_2\times Z_2^{\prime }$ DM stabilizing symmetry, where we assume that the DM particles are the inert Higgs boson, $\chi$ and $\varphi$. It is shown how the allowed parameter space, obtained previously in the absence of $\chi$ and $\varphi$, changes. The semiannihilation process in this model produces monochromatic neutrinos. The observation rate of these monochromatic neutrinos from the Sun at IceCube is estimated. Observations of high-energy monochromatic neutrinos from the Sun may indicate a multicomponent DM system.

Figure 1

Dark matter conversion (left) and semiannihilation (right).

Figure 2

Left: The relic abundance ${\Omega }_{{\chi }_1}{h}^2(x)$ (black curves) and ${\Omega }_{{\chi }_2}{h}^2(x)$ (blue curves) as a function of $x=\mu /T=[(m_1^{-1}+m_2^{-1})T{]}^{-1}$, with ${\sigma }_{0,1}=0.1$, ${\sigma }_{0,2}=6$, ${\sigma }_{0,12}=4.4$ (solid curves) or 0 (dashed curves), $m_1=200\mathrm{GeV}$, $m_2=160\mathrm{GeV}$, and $g_{*}=90$. Right: The total relic abundance ${\Omega }_T{h}^2$ as a function of ${\sigma }_{0,12}$, which parametrizes the size of the conversion ${\chi }_1{\chi }_1\to {\chi }_2{\chi }_2$.

Figure 3

The relic abundance ${\Omega }_{{\chi }_1}{h}^2(x)$ (black curve), ${\Omega }_{{\chi }_2}{h}^2(x)$ (blue curve) and ${\Omega }_{{\chi }_3}{h}^2(x)$ (red curve) as a function of $x=\mu /T=[(m_1^{-1}+m_2^{-1}+m_3^{-1})T{]}^{-1}$, where the input parameters are given in Eq. (17). Left: Without the nonstandard annihilation processes [Eqs. (2, 3)]. Right: ${\sigma }_{0,12}={\sigma }_{0,13}={\sigma }_{0,23}=5.2$, while ${\sigma }_{0,123}={\sigma }_{0,312}={\sigma }_{0,231}=0$, to show the effects of ${\chi }_i{\chi }_i\leftrightarrow {\chi }_j{\chi }_j$-type processes [Eq. (3)].

Figure 4

The relic abundance ${\Omega }_{{\chi }_1}{h}^2(x)$ (black curve), ${\Omega }_{{\chi }_2}{h}^2(x)$ (blue curve) and ${\Omega }_{{\chi }_3}{h}^2(x)$ (red curve) as a function of $x$ with ${\sigma }_{0,12}={\sigma }_{0,13}={\sigma }_{0,23}=0$, while ${\sigma }_{0,123}={\sigma }_{0,312}={\sigma }_{0,231}=5.1$, to show the effects of ${\chi }_i{\chi }_j\leftrightarrow {\chi }_k{X}_{ijk}$-type processes [Eq. (3)].

Figure 5

The total relic abundance ${\Omega }_T{h}^2$ as a function of ${\sigma }_{0,12}$ (solid curve) and ${\sigma }_{0,123}$ (dashed curve). Except for ${\sigma }_{0,12}$ (DM conversion) and ${\sigma }_{0,123}$ (semiannihilation), the input parameters are as given in Eq. (17).

Figure 6

Semiannihilation (left) and conversion (right).

Figure 7

$Y^{\chi }$ dependence of the relic abundances, ${\Omega }_T{h}^2$ (dashed curve), ${\Omega }_{\eta }{h}^2$ (black curve), ${\Omega }_{\chi }{h}^2$ [blue (light gray) curve], ${\Omega }_{\varphi }{h}^2$ [red (gray) curve], where $Y^{\chi }$ controls the size of the semiannihilation and conversion shown in Fig. 6. The input parameter values are given in Eq. (36).

Figure 8

Tree (left) and one-loop (right) level interactions with the quarks.

Figure 9

The allowed regime in the ${\lambda }_L({\lambda }_7)\mathrm{\text{−}}{m}_{{\eta }_R^0}$ plane for $({\delta }_1=10,{\delta }_2=10)\mathrm{GeV}$ with $m_{\chi }=m_{{\eta }_R^0}-10\mathrm{GeV}$, $m_{\varphi }=m_{{\eta }_R^0}-20\mathrm{GeV}$ and $M_k=1000\mathrm{GeV}$. The green (light gray) and red (dark gray) points are for ${\lambda }_L$ and ${\lambda }_7$, respectively.

Figure 10

The spin-independent cross section off the nucleon is plotted as a function of the DM mass. The green (light gray) and violet (dark gray) areas are for $\eta$ and $\varphi$ DM’s, respectively, where we have used $({\delta }_1=10,{\delta }_2=10)\mathrm{GeV}$ with $m_{\chi }=m_{{\eta }_R^0}-10\mathrm{GeV}$, $m_{\varphi }=m_{{\eta }_R^0}-20\mathrm{GeV}$ and $M_k=1000\mathrm{GeV}$.

Figure 11

The time evolution of the annihilation rates $\Gamma (\mathrm{SM})$ and $\Gamma (\nu )$, where $\tau =t/t_{\odot }$, and the input parameter values are those given in Eq. (36).