Dark Matter Candidates from Particle Physics and Methods of Detection

Abstract: The identity of dark matter is a question of central importance in both astrophysics and particle physics. In the past, the leading particle candidates were cold and collisionless, and typically predicted missing energy signals at particle colliders. However, recent progress has greatly expanded the list of well-motivated candidates and the possible signatures of dark matter. This review begins with a brief summary of the standard model of particle physics and its outstanding problems. We then discuss several dark matter candidates motivated by these problems, including WIMPs, superWIMPs, light gravitinos, hidden dark matter, sterile neutrinos, and axions. For each of these, we critically examine the particle physics motivations and present their expected production mechanisms, basic properties, and implications for direct and indirect detection, particle colliders, and astrophysical observations. Upcoming experiments will discover or exclude many of these candidates, and progress may open up an era of unprecedented synergy between studies of the largest and smallest observable length scales.

• The paper categorizes various dark matter candidates, linking theoretical models with experimental detection prospects.
• It details detection strategies including direct, indirect, and collider searches, and discusses their constraints and potential signals.
• It emphasizes interdisciplinary advances, suggesting that future collaborations in particle physics and astrophysics could unveil the true nature of dark matter.

Overview of Dark Matter Candidates and Detection Methods

The paper "Dark Matter Candidates from Particle Physics and Methods of Detection" by Jonathan L. Feng provides a comprehensive review of potential dark matter candidates and the methods to detect them, bridging the disciplines of particle physics and cosmology. The primary focus is on extending beyond the Standard Model (SM) to explain the nature of dark matter, highlighting the importance of this research for both astrophysics and particle physics.

Dark Matter Candidates

Feng categorizes the dark matter candidates based on their origins in particle physics models and their respective properties:

1. WIMPs (Weakly Interacting Massive Particles): WIMPs are well-motivated by the gauge hierarchy problem and naturally arise in theories such as supersymmetry. They interact through weak forces with masses around the electroweak scale (10 GeV - 1 TeV). The "WIMP miracle" suggests that WIMPs can achieve the observed dark matter relic density through thermal freeze-out.
2. SuperWIMPs: These are weakly-interacting massive particles produced in the decay of WIMPs after freeze-out. Their interaction through gravitational forces makes them extremely challenging to detect directly. Candidates include gravitinos and axinos, which inherit the right relic density from their parent WIMPs.
3. Sterile Neutrinos: Motivated by the extension of SM to include right-handed neutrinos, sterile neutrinos can obtain a mass through the see-saw mechanism. Although Lyman-alpha forest data constrain them, sterile neutrinos are considered warm dark matter solutions.
4. Axions: Proposed to solve the strong CP problem, axions could be cold dark matter through coherent oscillations in the early universe. The search for axions involves resonant enhancement of interactions with photons in magnetic fields.
5. Hidden Sector Models: These models propose dark matter candidates that do not interact with SM particles directly but may have significant interactions within a hidden sector. The WIMPless miracle in these models explains relic density by relating masses and coupling constants through a gauge symmetry similar to the SM.

Detection Methods

The paper explores several detection methodologies, assessing their viability for each candidate:

• Direct Detection: Involves measuring dark matter scattering off nuclei in ultra-sensitive detectors. This method is promising for WIMPs but is subject to various astrophysical and experimental uncertainties.
• Indirect Detection: Searches for annihilation or decay products of dark matter in cosmic rays or neutrinos. Indirect searches are of interest for both WIMPs and superWIMPs and can potentially identify signals in gamma rays or anti-matter.
• Collider Searches: Experiments at colliders like the LHC might produce dark matter particles, detectable through missing energy signatures. Precision measurements could potentially confirm dark matter relic densities implying dark matter identities.
• Astrophysical Signals: Evidence from astrophysical phenomena, such as the Cosmic Microwave Background (CMB) and Big Bang Nucleosynthesis (BBN), places constraints on decay lifetime and energy release of certain dark matter candidates like superWIMPs.

Implications and Future Directions

The paper emphasizes the interdisciplinary nature of dark matter research and its critical implications for understanding the universe. As new experiments and technologies advance, there will be opportunities to eliminate or confirm various theories, and possible synergies across observational and experimental methods could be pivotal in unveiling the nature of dark matter.

Future research will potentially address current limitations and uncertainties inherent in each detection method. The ongoing collaborations between particle physics, astrophysics, and cosmology could provide a comprehensive understanding of dark matter, leading to groundbreaking discoveries in fundamental physics.

Overall, the paper serves as an insightful resource for understanding the diverse landscape of dark matter candidates, methods of their detection, and the theoretical advancements required to anchor dark matter within the framework of modern physics.