Abstract
We present a simple model of two dark matter species with opposite millicharge that can form electrically neutral bound states via the exchange of a massive dark photon. If bound state formation is suppressed at low temperatures, a sub-dominant fraction of millicharged particles remains at late times, which can give rise to interesting features in the 21 cm absorption profile at cosmic dawn. The dominant neutral component, on the other hand, can have dipole interactions with ordinary matter, leading to non-standard signals in direct detection experiments. We identify the parameter regions predicting a percent-level ionisation fraction and study constraints from laboratory searches for dark matter scattering and dark photon decays.
Highlights
The defining property of dark matter (DM) is that it does not participate in electromagnetic interactions in the same way as visible matter
The cosmology of this so-called atomic DM has been studied in detail in the literature [12,13,14]
We focus on the process e + p → H + A where A is an on-shell dark photon
Summary
The defining property of dark matter (DM) is that it does not participate in electromagnetic interactions in the same way as visible matter. The idea of a sub-component of millicharged DM has recently received substantial attention because such a species would have interactions with baryons that become stronger as the Universe cools down This makes it possible to satisfy constraints on DMbaryon interactions from the Cosmic Microwave Background (CMB), while allowing for observable effects at later times. We assume that dark protons and dark electrons interact with each other through the exchange of a dark photon A with fine structure constant αD, such that the bound-state formation cross section is proportional to αD2 The cosmology of this so-called atomic DM has been studied in detail in the literature [12,13,14].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
