Deducing the nature of dark matter from direct and indirect detection experiments in the absence of collider signatures of new physics

Abstract: Despite compelling arguments that significant discoveries of physics beyond the standard model are likely to be made at the Large Hadron Collider, it remains possible that this machine will make no such discoveries, or will make no discoveries directly relevant to the dark matter problem. In this article, we study the ability of astrophysical experiments to deduce the nature of dark matter in such a scenario. In most dark matter studies, the relic abundance and detection prospects are evaluated within the context of some specific particle physics model or models (e.g. supersymmetry). Here, we attempt to develop a model-independent approach toward the phenomenology of weakly interacting massive particles in the absence of any discoveries at the Large Hadron Collider. In particular, we consider generic fermionic or scalar dark matter particles with a variety of interaction forms, and calculate the corresponding constraints from and sensitivity of direct and indirect detection experiments. The results may provide some guidance in disentangling information from future direct and indirect detection experiments.

Overview of Dark Matter Characterization through Astrophysical Experiments

The paper "Deducing the nature of dark matter from direct and indirect detection experiments in the absence of collider signatures of new physics" explores the intriguing aspect of identifying the characteristics of dark matter when typical high-energy collider experiments, like those at the Large Hadron Collider (LHC), offer no tangible evidence or discovery. The paper posits that even without direct detection of new physics at the LHC, dark matter can still be comprehensively studied through astrophysical detection methods.

Dark Matter Characterization Strategy

The paper adopts a model-independent approach, focusing on Weakly Interacting Massive Particles (WIMPs) as a plausible candidate for dark matter. The authors propose a strategy to analyze WIMPs based on their fundamental spin and interaction forms with Standard Model particles. The analysis includes both fermionic and scalar WIMPs, examining scalar, pseudoscalar, vector, axial vector, and tensor interactions.

Fermionic WIMPs

For fermionic WIMPs, the study outlines the derivation of constraints and prospects from both direct and indirect detection channels. Key points include:

• Relic Abundance: The relic abundance of fermionic WIMPs, calculated under certain ideal conditions (absence of resonances and coannihilations with other particles), shows its dependence on the WIMP mass and coupling values. Direct detection constraints, particularly from experiments like CDMS and XENON, highly restrict the parameter space, requiring careful consideration of these factors.
• Direct Detection: Scalar and vector couplings are severely constrained by current experimental limits, implying a necessity for heavy WIMP masses or alternative annihilation mechanisms like resonances or coannihilations to avoid overproduction in the early universe.
• Indirect Detection: From the analysis, axial and pseudoscalar interactions yield suppressed annihilation cross sections at low velocities, making detection via gamma-rays or charged particles improbable under standard conditions.

Scalar WIMPs

Scalar WIMPs, explored through scalar, vector, scalar-pseudoscalar, and vector-axial vector interactions, demonstrate similarly intricate constraints:

• Relic Density and Detection: Similar to fermionic cases, the measured relic density constrains scalar WIMPs, requiring heavy masses or specialized interaction conditions to align with experimental limits while achieving a relic density that matches cosmic observations.
• Detection Channels: The scalar WIMPs' scalar interactions with matter are potentially observable via direct detection, but vector interactions prove elusive due to velocity suppression effects in annihilation cross-sections. Neutrino telescopes show limited prospects in detecting scalar WIMPs due to their suppressed annihilation signatures.

Implications and Future Directions

The paper outlines the constraints provided by current and future astrophysical experiments, emphasizing their strategic utility in identifying the nature and properties of dark matter. If collider experiments remain unsuccessful in providing further insights, astrophysical detection methods can play a crucial role. The combined use of direct detection experiments, high-energy neutrino telescopes, and cosmic-ray observation tools can considerably narrow down the plausible characteristics of dark matter.

As detection technology advances and experimental limits are refined, these approaches can substantially impact our understanding of dark matter. Further investigation into resonance effects, coannihilation dynamics, and non-standard model candidates can also expand the scope of dark matter research beyond current paradigms. The strategies provided in this paper offer a comprehensive framework for future explorations in elucidating the true nature of dark matter.