Imprints of Non-thermal Wino Dark Matter on Small-Scale Structure

TL;DR

This paper investigates how non-thermally produced wino dark matter can be warm and affect small-scale cosmic structures, with implications for future 21 cm line observations.

Contribution

It provides a detailed analysis of the energy distribution and warmness of non-thermal wino dark matter, highlighting its impact on matter power spectra and potential observational signatures.

Findings

A significant fraction of wino dark matter can be warm for masses 100-500 GeV.

Warm wino dark matter leaves detectable imprints on matter power spectra.

Results applicable to various non-thermal wino production scenarios, including decay of moduli fields.

Abstract

We study how "warm" the wino dark matter is when it is non-thermally produced by the decays of the gravitino in the early Universe. We clarify the energy distribution of the wino at the decay of the gravitino and the energy loss process after their production. By solving the Boltzmann equation, we show that a sizable fraction of the wino dark matter can be "warm" for the wino mass m_{\tilde w} \sim 100-500 GeV. The "warmness" of the wino dark matter leaves imprints on the matter power spectra and may provide further insights on the origin of dark matter via the future 21 cm line survey. Our calculations can be applied to other non-thermal wino production scenarios such as the wino dark matter produced by the decay of the moduli fields.