Off-diagonal dark-matter phenomenology: Exploring enhanced complementarity relations in nonminimal dark sectors

In most multicomponent dark-matter scenarios, two classes of processes generically contribute to event rates at experiments capable of probing the nature of the dark sector. The first class consists of “diagonal” processes involving only a single species of dark-matter particle—processes analogous to those which arise in single-component dark-matter scenarios. By contrast, the second class consists of “off-diagonal” processes involving dark-matter particles of different species. Such processes include inelastic scattering at direct-detection experiments, asymmetric production at colliders, dark-matter co-annihilation, and certain kinds of dark-matter decay. In typical multicomponent scenarios, the contributions from diagonal processes dominate over those from off-diagonal processes. Unfortunately, this tends to mask those features which are most sensitive to the multicomponent nature of the dark sector. In this paper, by contrast, we point out that there exist natural, multicomponent dark-sector scenarios in which the off-diagonal contributions actually dominate over the diagonal. This then gives rise to a new, enhanced picture of dark-matter complementarity. In this paper, we introduce a scenario in which this situation arises and examine the enhanced picture of dark-matter complementarity which emerges.

Figure 1

Constraints on the parameter space of our scenario for the case of the vector interaction in Eq. (2.6). The upper, middle, and lower panels correspond respectively to the choices $m=\{10,100,1000\}\mathrm{GeV}$. The yellow shaded region is excluded by co-annihilation limits from Fermi-LAT for $f_2^{(V)}=0.5$. The magenta shaded region is excluded by combined direct-detection limits from LUX and XENON1T for the conservative case of $f_2^{(V)}=0$. Individual constraint contours from both LUX and XENON1T, as well as contours representing the projected reach of LZ, are shown for $f_2^{(V)}=0$ (solid curves), $f_2^{(V)}=0.5$ (dotted curves), and $f_2^{(V)}=1$ (dashed curves). The green line represents the naïve bound from CMS searches in contact-operator approximation. For further details, see text.

Figure 2

Constraints on the parameter space of our scenario for the case of the antisymmetric-tensor interaction in Eq. (2.6). The upper, middle, and lower panels correspond respectively to the choices $m=\{10,100,1000\}\mathrm{GeV}$. The yellow shaded regions are excluded by co-annihilation limits from Fermi-LAT, while the orange shaded regions are excluded by reionization limits and the gray shaded regions are excluded by x-ray searches. The magenta shaded region is excluded by combined direct-detection limits from LUX and PICO-60. Individual constraint contours from both LUX and PICO-60, as well as contours representing the projected reach of both LZ and PICO-500, are also shown. Note that the direct-detection curves for all benchmark choices of $f_2^{(T)}$ effectively coincide. The green line represents the naïve bound from CMS searches in contact-operator approximation. The green stars indicate the points in parameter space consistent with the purported 3.5 keV line observed in galactic clusters and in the Milky Way and Andromeda halos. For further details, see text.