Sensitivity of Hongmeng 21cm experiment on scattering dark matter

TL;DR

The Hongmeng lunar satellite experiment can significantly improve constraints on dark matter-baryon scattering by measuring the 21cm signal, even with limited observational strategies, potentially surpassing current limits within a month.

Contribution

This study demonstrates the potential of the Hongmeng project to enhance constraints on dark matter-baryon interactions through simulated 21cm observations and optimized observational strategies.

Findings

Hongmeng can tighten constraints on dark matter-baryon scattering cross-section by a factor of 21 after five years.

Even with minimal data collection, Hongmeng can improve current limits by a factor of 3 within one month.

The experiment can reach an upper limit of $4 imes 10^{-43} { m cm^2}$ on the cross-section for certain dark matter masses.

Abstract

Scattering between dark matter and baryon can cool intergalactic medium temperature and deepen the 21cm signal. Such interactions have been proposed to explain the unusually deep 21cm absorption signal reported by EDGES in 2018. This paper explores the potential to detect dark matter - baryon scattering with the Hongmeng project, an upcoming lunar orbiting satellite experiment dedicated to measuring global 21cm signal between redshifts $11-46$. We self-consistently forward-model the simulated sky temperature data, jointly varying both the astrophysical and foreground models. We show that even with a very conservative observational strategy in which the experiment only takes data when both the Earth and the Sun are shielded by the Moon, Hongmeng can tighten the current constraints on dark matter - baryon scattering cross-section $\sigma_0$ by a factor of 21 after the full mission which lasts for five years. The prospective upper limit on $\sigma_0$ can reach $4 \times 10^{-43} {\rm cm^2}$ for dark matter masses between 0.1 MeV and 0.4 GeV. Even after only one month of observation, a factor of 3 improvement relative to current $\sigma_0$ limits can be expected.