Maximizing Direct Detection with Highly Interactive Particle Relic Dark Matter.

Area of Science:

• Particle Physics
• Cosmology
• Astrophysics

Background:

• Direct detection experiments search for dark matter (DM) scattering off nuclei.
• Sub-GeV dark matter candidates are theoretically motivated but experimentally challenging.
• Current constraints suggest upper limits on the direct detection cross section.

Purpose of the Study:

• To estimate the maximum plausible direct detection cross section for sub-GeV dark matter.
• To propose a dark matter candidate that saturates this maximum cross section.
• To investigate the implications for dark matter detection and cosmological observations.

Main Methods:

• Estimation of maximum direct detection cross sections for sub-GeV dark matter.
• Introduction of a new dark matter candidate: highly interactive particle relics (HYPERs).
• Modeling of a dark sector phase transition affecting the mediator mass.

Main Results:

• Maximum direct detection cross sections for sub-GeV dark matter (10 keV-100 MeV) are estimated to be between 10^-36 and 10^-30 cm^2.
• HYPERs are shown to realize this maximum cross section.
• The proposed mechanism increases the direct detection cross section without altering dark matter abundance or violating Big Bang Nucleosynthesis and CMB constraints.

Conclusions:

• The direct detection cross section for sub-GeV dark matter has a plausible upper limit.
• Highly interactive particle relics (HYPERs) provide a viable candidate for dark matter that saturates this limit.
• The model offers a pathway to potentially detect sub-GeV dark matter through enhanced direct detection signals.