21 cm Absorption as a Probe of Dark Photons
Dark radiation could have injected soft photons into the primordial plasma with energies far below the Cosmic Microwave Background (CMB) temperature. Measurements of the low energy tail of the CMB spectrum therefore open a new window into the properties of dark radiation. We present an example model where dark radiation, composed of dark photons, resonantly oscillate into ordinary photons during the cosmic dark ages, enhancing the low energy tail of the CMB. Our scenario can explain the stronger than expected 21 cm absorption observed by the EDGES experiment.
Thanks goes to the organizers and to the Simons Foundation for making this engaging workshop possible. We would also like to thank Maxim Pospelov, Josef Pradler, and Alfredo Urbano for collaborating on the work described in this section. This work is supported by NSF CAREER grant PHY-1554858.
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