Complex Scalar Dark Matter vis-à-vis CoGeNT, DAMA/LIBRA and XENON100

TL;DR

The paper demonstrates that a complex scalar singlet extension of the SM (CSM) can accommodate light dark matter via a Higgs-portal interaction, yielding a DM candidate $A$ and two Higgs states $H_1$ and $H_2$ whose masses and mixing are constrained by relic density, LEP, and EWPO data. By scanning the six CSM parameters, the authors identify regions where the spin-independent cross section $\\sigma_{SI}$ aligns with CoGeNT and (partially) with DAMA/LIBRA and XENON100, typically with $M_A$ in the few- to tens-of-GeV range and a light $H_1$ that is mostly singlet. The study predicts distinctive LHC signatures, including sizable invisible decays $H_2\to AA$ and cascade decays $H_2\to H_1H_1$, offering robust tests of the scenario, and remains viable even if the direct DM hints are challenged. Overall, the CSM provides a coherent framework connecting light DM signals, relic density, and Higgs phenomenology with concrete collider expectations.

Abstract

The CoGeNT and DAMA/LIBRA experiments have found evidence for the spin-independent scattering from nuclei of a light dark matter (DM) particle, 7-12 GeV, which is not excluded by the XENON DM experiments. We show that this putative DM signal can be explained by a complex scalar singlet extension of the standard model (CSM), with a thermal cosmological DM density, and a Higgs sector that is consistent with LEP constraints. We make predictions for the masses, production, and decays of the two Higgs mass eigenstates and describe how the Higgs and DM particles can be discovered at the LHC.

Figures (10)

• Figure 1: Feynman diagrams that contribute to the annihilation cross setion of $A$. All processes are mediated via the two Higgs eigenstates $H_{1,2}$.
• Figure 2: Feynman diagrams associated with the spin-independent direct detection of $A$. As in annihilations, the Higgs bosons are the mediating fields between the DM and the nuclear target.
• Figure 3: Range of $M_A$ and $\sigma_{SI}$ values. The 90% C.L. boundary of the CoGeNT signal region is denoted by the solid (black) contour. The signal region of the DAMA/LIBRA data, with no channeling effects, is enclosed by a dotted (green) contour. The XENON100 exclusion limit is given by the short-dashed (black) boundary. The DAMA/LIBRA region with channeling is shown by the bold dash-dotted (black) contour. All contours are shown at the $90\%$ C.L. The measured relic density can be saturated below the $H_{1}$ resonance (open blue boxes), above the $H_{1}$ resonance (filled red circles), with the $AA\to H_{1}H_{1}$ channel open during freeze-out (black crosses).
• Figure 4: Relic abundance of $A$ versus the $H_{1}$ mass with $M_{H_{2}} = 120$ GeV and a $H_{1}$ SM-Higgs content of $10^{-4}$ in (a) the CoGeNT region with $M_{A}=10$ GeV and (b) XENON100 exclusion region with $M_{A}=50$ GeV. The measured relic density can be saturated below the $H_{1}$ resonance (blue open boxes), above the $H_{1}$ resonance (red filled circles), with the $AA\to H_{1}H_{1}$ channel open during freeze-out (black crosses). This color notation is respected in subsequent figures unless otherwise noted.
• Figure 5: Mass of the heavy Higgs versus that of the light Higgs for (a) CoGeNT $90\%$ C.L. signal region and (b) XENON100 allowed region. The $AA$ annihilation takes place above (below) the $H_1$ resonance for the blue boxes (red circles).