Global tests of dark matter models

There are various DM candidates within the DM particle zoo, such as Weakly Interactive Massive Particles (WIMPs), axions, axion-like particles, PBHs, sterile neutrinos, and more. The mass spectrum and interaction strength of these candidates with standard model particles span 80 magnitudes. Each of these DM candidates has motivations, but we cannot determine which one is correct. Following Bayesian theory as illustrated in Fig 3, our current DM likelihoods offer minimal information. Thus, increasing the complexity of the DM model without solid motivation will not yield useful posterior information.

If seriously considering the relic density predicted by ΛCDM, with the relic abundance measured value around 0.1 (by PLANCK), the amount of DM production shall be treated as a signal.Under the freeze-out framework (similar assumption used to predict BBN), the correct relic density sets important lower limits on the parameter space of the dark matter model, and this constraint is usually a complementary to the colliders and DM direct detection which set upper limits on dark matter parameter space.This is a very good hint that the dark matter model parameter space is finite for exploration, if combined relic density, collider null signal results, and DM direct and indirect detection.

During the early universe, all couplings contribute to the calculation of the annihilation cross-section, but there are specific regions of the dark matter mass where some couplings have a dominant impact.In Fig 4, we demonstrate the individual role of each interaction in determining the relic density as a function of the dark matter mass.The grey shaded region, which falls outside the 95% confidence limit imposed by the Planck constraint, is excluded.For certain values of dark matter masses, a very low relic density is observed. This means that for those masses, it is possible to satisfy the relic density requirement even with very small coupling strengths.

Our research focuses on minimal DM models, effective field theories, and UV-completed models, akin to Occam’s Razor.Following the standard model’s development, we have explored minimal DM models¹²³⁴⁵ and effective field theories (EFTs)⁶⁷⁸⁹. Utilizing EFT, our work in ⁶¹⁰ describes features across various WIMP models, with their Table I replicable for interested students.Papers ¹¹⁸ refine our approach by considering experimental constraints and analyzing CP-conserving and CP-violating scenarios in singlet Majorana DM. We also investigate scalar DM particle models, including singlet DM ⁴ and inert doublet DM ², particularly intriguing for potential testing via LHC compressed spectrum searches¹².Two experiments from Fermilab, E989 and CDF II, reported anomalies in muon g-2 and W-boson mass, potentially indicating new low-energy physics.A minimal extension of the Standard Model involves an additional scalar doublet, enhancing the W-boson mass via loop corrections.The inert two Higgs doublet model can accommodate the new W-boson mass and suggests a dark matter mass between 54 and 74 GeV ¹³.Three feasible parameter regions are identified: $S A$ coannihilation, Higgs resonance, and $S S \to WW*$ annihilation.These regions can be tested by the High Luminosity Large Hadron Collider, constrained by direct detection experiments, or produce detectable gamma-ray and antiproton signals observed by Fermi-LAT and AMS-02, see¹³.

For UV-completed models, we mainly work within the framework of Supersymmetry (SUSY), including the Minimal Supersymmetric Standard Model (MSSM) and the Next-to-Minimal Supersymmetric Standard Model (NMSSM).SUSY provides a robust framework for dark matter and strong motivation for its study, including DM candidate neutralino¹⁴ and sneutrino¹⁵.We applied global fitting analysis to identify the parameter space favored by current experimental data.The NMSSM offers a potential solution for various anomalies while meeting constraints such as the Higgs mass, collider data, flavor physics, dark matter relic density, and direct detection experiments.Lighter electroweakinos and sleptons may contribute to the muon g-2 and W-boson mass, with bino-like neutralino dark matter mass in the 180–280 GeV range, which current direct detection experiments could soon test¹⁶.Additionally, the NMSSM explains gamma-ray excesses at the Galactic center and antiproton excesses observed by Fermi-LAT and AMS, with a ~60 GeV bino-like neutralino accounting for these observations¹⁷.