Viable Twin Cosmology from Neutrino Mixing

Understand

Twin Higgs models solve the little hierarchy problem without introducing new colored particles, however they are often in tension with measurements of the radiation density at late times.

• Here we explore viable cosmological histories for Twin Higgs models.
• In particular, we show that mixing between the SM and twin neutrinos can thermalize the two sectors below the twin QCD phase transition, significantly reducing the twin sector's contribution to the radiation density.
• The requisite twin neutrino masses of order 1-20 GeV and mixing angle with SM neutrinos of 10^{-3} - 10^{-5} can be probed in a variety of current and planned experiments.