- The paper presents experimental anomalies and theoretical models that expand dark matter research beyond the conventional WIMP paradigm.
- It evaluates cosmological observations and signatures, spotlighting the critical 1-100 MeV mass range in dark matter studies.
- The study advocates a complementary multi-technique approach, combining large-scale detectors with targeted small-scale and collider experiments.
New Ideas in Dark Matter: A Comprehensive Review
The document "US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report" presents an extensive overview of various research directions in the field of dark matter, as discussed during a community workshop. The paper is divided into several focused sections, each addressing different facets of dark matter research, ranging from experimental anomalies to theoretical models and future experimental proposals. This essay summarizes the key components and conclusions of the report, highlighting their implications for future dark matter research.
Experimental Anomalies and Hints
The report discusses various experimental anomalies that have the potential to indicate new physics relevant to dark matter. Notable among these are the anomalous magnetic moment of the muon, the proton radius puzzle, and a possible new boson indicated by decays of excited 8Be nuclei. Each of these anomalies suggests the potential involvement of new particles with masses in the MeV to GeV range. The 8Be anomaly, in particular, has motivated proposals for nuclear experiments to explore this potential new boson. Importantly, these anomalies highlight the need for ongoing experimental and theoretical scrutiny to further understand their implications for dark matter.
Cosmology and Astrophysics
The paper emphasizes the critical role of cosmological observations in constraining dark matter properties. Cosmological data, such as the cosmic microwave background (CMB), provide stringent constraints on dark matter annihilation and decay processes, shedding light on the viability of light dark matter candidates. Moreover, observations of the universe's small-scale structure have prompted interest in self-interacting dark matter models, which could explain certain galactic phenomena unexplained by standard cold dark matter models. These interactions are suggested to occur via mediators in the MeV mass range, underscoring the importance of this mass scale in current research.
Models and Relic Density
In exploring theoretical models, the report covers a broad spectrum of dark matter candidates, including strongly interacting massive particles (SIMPs), elastically decoupling relics (ELDERs), and dynamical dark matter (DDM). These models propose dark matter particles with varied interaction histories and mass scales, expanding the possibilities beyond the conventional WIMP paradigm. For instance, SIMPs and ELDERs involve strong self-interactions mediated by MeV-scale particles, while DDM suggests a complex dark sector with many components. Each model provides distinct experimental signatures, emphasizing the diversity of viable dark matter scenarios.
Complementarity and Future Experiments
The review highlights the complementarity between different experimental approaches to dark matter detection. Large-scale experiments like LZ and XENONnT focus on probing WIMP-like dark matter through direct detection, while small-scale efforts target low-mass dark matter candidates. The paper also discusses the potential of particle colliders and fixed-target experiments in exploring light dark matter and mediators. The emerging consensus is that a multi-pronged approach, combining diverse experimental techniques, is essential to cover the vast parameter space of dark matter candidates effectively.
Key Conclusions and Recommendations
The report calls for continued investment in a broad array of dark matter experiments, both large and small-scale. It identifies the 1 to 100 MeV mass range as particularly promising, given its relevance to several theoretical and experimental frameworks. Furthermore, the document stresses the importance of maintaining robust theoretical support to guide experimental efforts and interpret their results. In conclusion, the report outlines a promising path forward for dark matter research, emphasizing the integration of experimental and theoretical efforts across multiple scientific domains to unravel the mysteries of dark matter.