Speaker
Description
We study a simplified freeze-in dark matter model with a dark matter $\chi$ and a light scalar mediator $\phi$ which couples only to neutrinos in the Standard Model. We point out two possible UV origins generating extremely small scalar and pseudo-scalar couplings between $\phi$ and neutrinos. We find benchmarks to realize the correct relic density with and without re-annihilation scheme by solving the coupled differential equations for number and energy densities of $\phi$ and $\chi$. We investigate the temperature evolution in the dark sector and the effect of decay and inverse decay of $\phi$ on BBN. We find tension in our simplified model between satisfying the cosmological constraint (relic abundance and BBN) and explaining the small scale structure problem with self-interacting dark matter argument.
