Physics

Reconciling the existence of dark matter with the Standard Model (SM) of particle physics involves extending the current framework to account for new particles and interactions. Here are some key approaches future quantum field theories might take, considering gauge symmetry, supersymmetry (SUSY) constraints, and potential new forces or mediators:

1. Gauge Symmetry Extensions

• Additional Gauge Groups: One approach is to extend the gauge symmetry of the Standard Model by introducing new gauge groups, such as $U(1{)}^{\prime }U(1)’$, $SU(2{)}^{\prime }SU(2)’$, or others. Dark matter particles could be charged under these new groups while remaining neutral under the Standard Model gauge interactions.
• Kinetic Mixing: A $U(1{)}^{\prime }U(1)’$ gauge boson (sometimes called a dark photon) could mix kinetically with the Standard Model’s hypercharge gauge boson. This mixing allows for indirect interactions between dark matter and ordinary matter, providing a mechanism to potentially detect dark matter through weak electromagnetic-like interactions.

2. Supersymmetry (SUSY)

• Neutralino as a Dark Matter Candidate: In SUSY models, the lightest supersymmetric particle (LSP) is often stable due to R-parity conservation. The neutralino, a mixture of the supersymmetric partners of the photon, $ZZ$ boson, and Higgs bosons, is a popular dark matter candidate because it is electrically neutral and interacts weakly.
• Extended SUSY Models: Models beyond minimal SUSY, such as the Next-to-Minimal Supersymmetric Standard Model (NMSSM), introduce additional fields, like singlet superfields, which can modify the neutralino properties and provide better dark matter candidates.

3. New Fundamental Forces

• Mediator Particles: The introduction of new mediator particles (scalar, pseudoscalar, vector, or axial-vector bosons) that couple to both dark matter and Standard Model particles can bridge the two sectors. These mediators can be responsible for new interactions, potentially observable in direct detection experiments or at colliders.
• Dark Higgs Mechanism: Similar to the Higgs mechanism in the Standard Model, a dark sector Higgs field could break a new symmetry and give mass to dark sector particles. This mechanism would imply the existence of a dark Higgs boson, which could be probed through its mixing with the Standard Model Higgs boson.

4. Non-WIMP Models

• Axions and Axion-Like Particles (ALPs): Axions are hypothetical particles proposed to solve the strong CP problem in QCD and are also candidates for dark matter. They interact very weakly with Standard Model particles, primarily through their coupling to photons and possibly other gauge bosons.
• Sterile Neutrinos: These are neutrinos that do not interact via the weak force and can serve as dark matter candidates. They interact only gravitationally and potentially through a small mixing with active neutrinos.

5. Hidden or Secluded Sectors

• Hidden Sector Models: These models propose that dark matter resides in a hidden sector that communicates with the Standard Model via very weak interactions. This can be through portals like the Higgs portal, vector portal (dark photon), or neutrino portal.
• Secluded Dark Matter: Here, dark matter particles interact primarily with each other through forces confined to the dark sector, with limited interaction with the Standard Model.

Each of these approaches integrates dark matter into the broader framework of particle physics by either extending the symmetry structure, introducing new particles, or proposing novel interactions that maintain consistency with existing observations while providing pathways to detect dark matter. Future experiments in astrophysics, cosmology, and high-energy physics will be crucial in distinguishing which, if any, of these theoretical frameworks correctly describe the nature of dark matter.