Resonant Forbidden CP Asymmetry from Soft Leptons

Area of Science:

• Particle Physics
• Cosmology
• Early Universe Physics

Background:

• Explaining the observed baryon asymmetry in the universe is a major challenge in cosmology.
• Current models often require new particles and quantum corrections to generate CP asymmetry for leptogenesis.
• Standard Model (SM) physics alone is insufficient to explain this asymmetry.

Purpose of the Study:

• To demonstrate that a large CP asymmetry, crucial for leptogenesis, can arise from SM leptons.
• To propose a mechanism relying on thermal effects and resummation of soft leptons.
• To explore implications for low-scale leptogenesis and dark matter cogenesis.

Main Methods:

• Applying finite-temperature field theory techniques.
• Utilizing resummation of soft leptons at non-zero temperatures.
• Analyzing CP asymmetry through thermally resummed lepton contributions.

Main Results:

• A significant CP asymmetry, kinematically forbidden in vacuum, can be resonantly enhanced by up to seven orders of magnitude.
• This resonant enhancement from soft leptons is robust and protected by controlled widths under finite-temperature perturbation theory.
• The mechanism allows for secluded flavor effects and quantifies CP asymmetries in leptogenesis.

Conclusions:

• The study presents a novel, minimal model for leptogenesis using only SM leptons.
• This approach facilitates low-scale leptogenesis and dark matter cogenesis.
• The findings offer a simpler and more controlled explanation for the universe's matter-antimatter imbalance.