HEP
In the literature: open
Which mechanism produced the cosmic baryon asymmetry?
In plain words
For every billion antiquarks there were about a billion and one quarks in the early universe. Something broke the matter-antimatter balance, and we do not know what.
Precise statement
Explain $\eta_B = n_B/n_\gamma \sim 6.1e-10$ (CMB and BBN) satisfying the Sakharov conditions, given that SM CP violation and the SM crossover fail by many orders of magnitude. An answer is a mechanism (thermal or resonant leptogenesis, electroweak baryogenesis, Affleck-Dine, or others) with an independent experimental confirmation.
What would settle it
Laboratory confirmation of the ingredients of one mechanism, for example lepton number violation plus leptonic CP violation plus heavy neutral leptons for leptogenesis.
Related problems
- More general than Can electroweak baryogenesis survive the electron EDM bound?
- More general than Do GeV-scale heavy neutral leptons realize low-scale leptogenesis?