Dark sequential $Z\prime$ portal: Collider and direct detection experiments

We revisit the status of a Majorana fermion as a dark matter candidate when a sequential $Z^{\prime }$ gauge boson dictates the dark matter phenomenology. Direct dark matter detection signatures rise from dark matter-nucleus scatterings at bubble chamber and liquid xenon detectors, and from the flux of neutrinos from the Sun measured by the IceCube experiment, which is governed by the spin-dependent dark matter-nucleus scattering. On the collider side, LHC searches for dilepton and monojet + missing energy signals play an important role. The relic density and perturbativity requirements are also addressed. By exploiting the dark matter complementarity we outline the region of parameter space where one can successfully have a Majorana dark matter particle in light of current and planned experimental sensitivities.

Figure 1

Feynman diagrams relevant for dark matter annihilation. The first encompasses all possible annihilations into SM particles through the $Z^{\prime }$ portal, whereas the second encompasses the self-annihilation into $Z^{\prime }$ gauge bosons.

Figure 2

Feynman diagram relevant for direct detection. The dark matter scattering off nucleons occurs via the $Z^{\prime }$ t-channel exchange.

Figure 3

Feynman diagrams relevant for collider probes. The first diagram represents monojet searches for dark matter, where the $Z^{\prime }$ decays invisibly with a jet being radiated from the initial state. The second accounts for the resonance production of the $Z^{\prime }$ gauge boson. The latter is not particularly sensitive to dark matter, but it strongly restricts the $Z^{\prime }$ mass with great impact to this particular model.

Figure 4

Summary plot for $g_{\chi }=0.1$. The solid back curve outlines the region of parameter space with the correct relic density. From left to right, in dashed blue is the parameter space excluded by IceCube; the orange solid line represents the current bound from PICO, the dashed green line the current bound from LUX on SD scattering off neutrons with 129.5 kg-year exposure, and the solid green line the projected bound from XENON1T on SD scattering off neutrons with $34\mathrm{d}\times \mathrm{t}$ of exposure; further right in light green, we show the projected sensitivity from XENON1T on SD scattering off neutrons with $2\mathrm{y}\times \mathrm{t}$ exposure; the upper region inside the dashed black line delimits the nonperturbative regime; the dashed red curve exhibits the parameter space excluded by the LHC based on monojet data; solid (dotted) blue vertical lines delimit the current (projected) LHC exclusion regions derived from dilepton data.

Figure 5

Exclusion limits for $g_{\chi }=1$. The solid back curve outlines the region of parameter space with the correct relic density. From left to right, in dashed blue is the parameter space excluded by IceCube; the orange solid line represents the current bound from PICO, the dashed green line the current bound from LUX on SD scattering off neutrons with 129.5 kg-year exposure, and the solid green line the projected bound from XENON1T on SD scattering off neutrons with $34\mathrm{d}\times \mathrm{t}$ of exposure; further right in light green, we show the projected sensitivity from XENON1T on SD scattering off neutrons with $2\mathrm{y}\times \mathrm{t}$ exposure; the upper region inside the dashed black line delimits the nonperturbative regime; the dashed red curve exhibits the parameter space excluded by the LHC based on monojet data; solid (dotted) blue vertical lines delimit the current (projected) LHC exclusion regions derived from dilepton data.

Figure 6

Exclusion limits for $g_{\chi }=4\pi$. The solid back curve outlines the region of parameter space with the correct relic density. From left to right, in dashed blue is the parameter space excluded by IceCube; the orange solid line represents the current bound from PICO, the dashed green line the current bound from LUX on SD scattering off neutrons with 129.5 kg-year exposure, and the solid green line the projected bound from XENON1T on SD scattering off neutrons with $34\mathrm{d}\times \mathrm{t}$ of exposure; further right in light green, we show the projected sensitivity from XENON1T on SD scattering off neutrons with $2\mathrm{y}\times \mathrm{t}$ exposure; the upper region inside the dashed black line delimits the nonperturbative regime; the dashed red curve exhibits the parameter space excluded by the LHC based on monojet data; dot-dashed (dotted) blue vertical lines delimit the current (projected) LHC exclusion regions derived from dilepton data.