Super heavy dark matter from inflationary Schwinger production

We consider a simple setup with a dark sector containing dark electrons charged under an Abelian <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>U</a:mi><a:mo stretchy="false">(</a:mo><a:mn>1</a:mn><a:msub><a:mo stretchy="false">)</a:mo><a:mi>D</a:mi></a:msub></a:math> gauge symmetry. We show that, if the massless dark photon associated to the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>U</e:mi><e:mo stretchy="false">(</e:mo><e:mn>1</e:mn><e:msub><e:mo stretchy="false">)</e:mo><e:mi>D</e:mi></e:msub></e:math> is produced during inflation in such a way as to form a classical dark electric field, then dark electron-positron pairs are also produced close to the end of inflation via the Schwinger effect even if they are very massive. For large enough dark electric force, dark electrons with masses larger than the Hubble scale can be produced which are nonrelativistic at production and throughout their cosmic evolution. They can account for the dark matter abundance today for masses in the range <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mo>∼</i:mo><i:mn>100</i:mn><i:mtext> </i:mtext><i:mtext> </i:mtext><i:mi>GeV</i:mi></i:math> to <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:msup><k:mn>10</k:mn><k:mn>17</k:mn></k:msup><k:mtext> </k:mtext><k:mtext> </k:mtext><k:mi>GeV</k:mi></k:math> and up to 6 orders of magnitude larger than the Hubble scale at the end of inflation where purely gravitational production is exponentially suppressed. We examine the regime where the dark electrons do not thermalize with the dark photons throughout their cosmic history and assume negligible kinetic mixing with the visible <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi>U</m:mi><m:mo stretchy="false">(</m:mo><m:mn>1</m:mn><m:mo stretchy="false">)</m:mo></m:math> so they remain decoupled from the Standard Model thermal bath as well. Thus, the final dark matter relic abundance is determined only by the initial inflationary Schwinger production and redshifting after reheating. Published by the American Physical Society 2024