Dark Sectors 2016 Workshop: Community Report (1608.08632v1)

Abstract: This report, based on the Dark Sectors workshop at SLAC in April 2016, summarizes the scientific importance of searches for dark sector dark matter and forces at masses beneath the weak-scale, the status of this broad international field, the important milestones motivating future exploration, and promising experimental opportunities to reach these milestones over the next 5-10 years.

• The paper presents a comprehensive assessment of dark sectors, detailing theoretical portals and diversified experimental strategies beyond standard WIMP targets.
• It recommends approaches such as direct detection, fixed-target, and collider experiments to probe sub-GeV dark matter and mediator signatures.
• The report underscores the need for innovative technologies and interdisciplinary collaboration to uncover the hidden structure of dark sectors.

Summary of the "Dark Sectors 2016 Workshop: Community Report"

The "Dark Sectors 2016 Workshop: Community Report" presents a comprehensive assessment of the status and future trajectory of research into dark sectors, which include prospective extensions of the Standard Model of particle physics to accommodate dark matter (DM). This report, focused on experiments in the sub-electroweak mass range, highlights the necessity for a diversified scientific approach to explore DM through multiple experimental strategies, including both direct detection and accelerator-based methods.

Theoretical Context and Motivations

The report outlines the various portals through which dark sectors might interact with the Standard Model. Among these, the vector portal involving kinetically mixed dark photons, and the Higgs and neutrino portals, are prominent. These theories postulate new particles, such as the dark photon—a gauge boson associated with a hypothetical dark U(1) force that kinetically mixes with the photon. Such interactions potentially offer explanations for deviations in observed phenomena like the $(g-2)_\mu$ discrepancy, signaling new physics.

Central motivations include addressing the unexplained 80% of cosmic matter content—dark matter—and understanding its interactions with visible matter through potentially observable signatures. The report emphasizes a need for a vast parameter space exploration given the absence of Weakly Interacting Massive Particles (WIMPs) in anticipated mass ranges. In particular, light (sub-GeV) DM candidates present viable targets with unique phenomenological signatures requiring innovative doctrine and methodology.

Experimental Strategies and Proposals

The report laments the incomplete testing of sub-GeV dark sectors, especially those involving light mediators like dark photons. Recommended experimental approaches include:

1. Direct Detection Experiments: Utilizing materials sensitive to low-energy thresholds to search for DM-electron interactions, critically extending detection capabilities to masses down to a few keV. This calls for leveraging progress in semiconductor and superconductor technologies.
2. Fixed-Target Experiments: Employing electron and proton beams to probe dark photons and other mediator particles with missing momentum or invariant mass techniques. This requires addressing experimental challenges such as improving detectors' sensitivity to rare processes while battling significant backgrounds.
3. Collider and Beam-Dump Experiments: Using high-luminosity $e^+e^-$ colliders, such as Belle II, or high-energy proton colliders, including those at the LHC, and exploring novel configurations to maximize their sensitivity to low-mass mediators and potential new states within dark sectors.
4. Rich Dark Sector Models: Encouraging searches beyond the minimal dark photon model, capturing scenarios with complex dynamics, potential strong coupling effects, and additional states or forces uncoupled from visible matter. This involves innovative theoretical constructs like non-Abelian dark sectors and rich phenomenological explorations.

Implications and Forward-Looking Statements

The report underscores the intricate interdependency between theoretical advancements and experimental innovations. In order to validate or refute a range of dark sector models, a symbiotic relationship fostering cross-disciplinary dialogue and collaborations is indispensable. The implications of such research stretch beyond particle physics into cosmic evolution and structure formation, potentially unraveling key facets of the universe's hidden sector.

Moreover, the report speculates that breakthroughs in understanding dark sectors will be contingent upon developing and integrating new detection technologies, comprehensively analyzing experimental designs, and adopting scalable, innovative approaches to cope with sophisticated theoretical landscapes.

By articulating these nuanced perspectives and consolidating our grasp on these emergent sectors, the scientific community can shape a transformative narrative around one of the foremost questions in modern physics—the true essence of dark matter and the architecture of the dark universe.