# Baryon-Dark matter interaction in presence of magnetic fields in light of EDGES signal

## TL;DR

This paper explores how cosmic magnetic fields and baryon-dark matter interactions jointly influence the 21 cm signal observed by EDGES, deriving bounds on magnetic field strength, dark matter mass, and interaction cross-section.

## Contribution

It investigates the combined effects of magnetic fields and baryon-dark matter interactions on the EDGES signal, providing new bounds and showing the allowed magnetic field range can increase significantly.

## Key findings

- Strong magnetic fields require larger baryon-dark matter cross-sections to explain EDGES.
- Upper bound on magnetic field strength is $3.48\times10^{-6}$ G for dark matter mass $\lesssim 10^{-2}$ GeV.
- Allowed primordial magnetic field range can increase by three orders of magnitude.

## Abstract

We have shown that in presence of a cosmic magnetic field the bounds on baryon dark matter cross-section ($\hat \sigma$), dark-matter mass ($m_d$) and values of the magnetic field ($B_0$) can strongly influence each other. This requires to rework the bounds on $\hat \sigma\,$, $m_d$ and $B_0$ which can explain the observed absorption signal by EDGES collaboration. The upper limit on the magnetic field strength can modify in presence of baryon-dark matter interaction cross-section. In the presence of a strong magnetic field, a large baryon-dark matter interaction cross-section is required to balance magnetic heating of gas to explain the EDGES signal as compared to a weak magnetic field. Subsequently, the strong magnetic-fields can even erase the 21 cm signal--this gives an upper bound on the strength of magnetic-fields, dark-matter mass and baryon-dark matter cross-section. In the special case when $\hat \sigma$=0, one can recover the bound on magnetic field strength calculated in [1]. In this work we find that the allowed range of the primordial magnetic field can increase by three orders of magnitude in comparison with [1]. We get upper bound on the magnetic field strength: $3.48\times10^{-6}$ G for the dark matter mass $\lesssim 10^{-2}$ GeV.