Abstract
We consider a chiral gauge theory from which light composite Dirac neutrinos dynamically emerge, augmented by a QCD axion to solve the strong CP problem. We show that an interplay between the composite sector and the axion can also simultaneously lead to successful baryogenesis and generate a correct dark matter abundance via "co-genesis" without contradicting present constraints. We predict $\Delta N_{\rm eff} \geq 0.14$ and $m_a$ in the range $O(1)\>{\rm \mu eV}$--$O(10)\>{\rm meV}$, which can be firmly tested by upcoming CMB experiments and axion searches.
Highlights
We show that an interplay between the composite sector and the axion can simultaneously lead to successful baryogenesis and generate a correct dark matter abundance via “cogenesis” without contradicting present constraints
Why are neutrinos so light? Why does lepton number appear to be conserved so well? These questions have a beautiful answer for Majorana neutrinos—gauge invariance dictates that neutrino masses and associated lepton number violation must originate from an irrelevant interaction suppressed by a large mass scale
We show that just such composite sector for explaining small Dirac neutrino masses augmented by a QCD axion to solve the strong CP problem can simultaneously provide a correct DM abundance and successful baryogenesis, over a large viable parameter range
Summary
These questions have a beautiful answer for Majorana neutrinos—gauge invariance dictates that neutrino masses and associated lepton number violation must originate from an irrelevant interaction suppressed by a large mass scale. Do we have a compelling theoretical plot where small neutrino masses and associated lepton number conservation emerge from gauge invariance? Light Dirac neutrinos and lepton number conservation emerge from gauge invariance.. We show that just such composite sector for explaining small Dirac neutrino masses augmented by a QCD axion to solve the strong CP problem (i.e., make the neutron EDM vanish) can simultaneously provide a correct DM abundance and successful baryogenesis, over a large viable parameter range. DM and baryon asymmetry are generated through an intimate interplay between the axion and composite sectors via the “cogenesis” mechanism [3,4,5], and it is this interplay that permits a large range of parameters in which all four problems are simultaneously solved
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