Twin Cogenesis
  We investigate a cogenesis scenario within the twin Higgs setup which can
naturally explain the nature of dark matter, the cosmic coincidence puzzle,
little hierarchy problem, leptogenesis and the tiny neutrino masses. Three
heavy Majorana neutrinos are introduced to the standard model sector and the
twin sector respectively, which explain the tiny neutrino masses and generate
the lepton asymmetry and the twin lepton asymmetry at the same time. The twin
cogenesis scenario is general and applies to any viable twin Higgs model
without hard $\mathbb{Z}_2$ breaking and evading the $\Delta N_{\rm eff}$
constraint. We demonstrate twin cogenesis in two models: fraternal twin Higgs
model, and neutrino-philic twin two Higgs doublet model, a newly proposed model
to lift the twin neutrino masses with spontaneous $\mathbb{Z}_2$ breaking. The
MeV scale dark photon ensures the energy in the twin sector as well as the
symmetric component of twin sector particles can be depleted. The lightest twin
baryons are the dark matter candidates with masses approximately 5.5~GeV, which
explain naturally the amount of dark matter and visible matter in the Universe
are of the same order.
