Abstract
Adding an axion-like particle (ALP) to the Standard Model, with a field velocity in the early universe, simultaneously explains the observed baryon and dark matter densities. This requires one or more couplings between the ALP and photons, nucleons, and/or electrons that are predicted as functions of the ALP mass. These predictions arise because the ratio of dark matter to baryon densities is independent of the ALP field velocity, allowing a correlation between the ALP mass, ma, and decay constant, fa. The predicted couplings are orders of magnitude larger than those for the QCD axion and for dark matter from the conventional ALP misalignment mechanism. As a result, this scheme, ALP cogenesis, is within reach of future experimental ALP searches from the lab and stellar objects, and for dark matter.
Highlights
Electrons and nucleons and find them to be orders of magnitude larger than for the QCD axion [2,3,4,5] and for dark matter from conventional misalignment [6,7,8] for the axion-like particle (ALP)
The charge asymmetry in the ALP condensate Yθ gets transferred via its SM couplings to particle-antiparticle asymmetries of SM particles in the thermal bath, and at temperatures above the electroweak scale the electroweak processes convert this to a baryon asymmetry relative to entropy of
Spontaneous baryogenesis [12, 13] relies on the angular velocity of the condensate that acts as an effective chemical potential for a thermal bath, generating a baryon asymmetry for the quarks using a baryon number violating interaction
Summary
We take the Effective Field Theory (EFT) at the weak scale to be the Standard Model together with an ALP that has some non-zero couplings to SM particles. In the weak scale EFT, the most general set of interactions between the ALP and SM particles up to dimension 5 is. The key that allows the ALP to generate a baryon asymmetry and account for the dark matter abundance is its cosmological evolution: θmust be non-zero at the weak scale. A relatively flat potential for S is needed, together with a large initial field value, for example from inflation.
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