Sterile neutrino portal dark matter from semiproduction

In this paper, we study the feeble sterile neutrino portal dark matter under the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msub><a:mi>Z</a:mi><a:mn>3</a:mn></a:msub></a:math> symmetry. The dark sector consists of one fermion singlet <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>χ</c:mi></c:math> and one scalar singlet <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>χ</e:mi></e:math>, which transform as <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi>χ</g:mi><g:mo stretchy="false">→</g:mo><g:msup><g:mi>e</g:mi><g:mrow><g:mi>i</g:mi><g:mn>2</g:mn><g:mi>π</g:mi><g:mo>/</g:mo><g:mn>3</g:mn></g:mrow></g:msup><g:mi>χ</g:mi><g:mo>,</g:mo><g:mi>ϕ</g:mi><g:mo stretchy="false">→</g:mo><g:msup><g:mi>e</g:mi><g:mrow><g:mi>i</g:mi><g:mn>2</g:mn><g:mi>π</g:mi><g:mo>/</g:mo><g:mn>3</g:mn></g:mrow></g:msup><g:mi>ϕ</g:mi></g:math> under the <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:msub><k:mi>Z</k:mi><k:mn>3</k:mn></k:msub></k:math> symmetry. Regarding fermion singlet <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi>χ</m:mi></m:math> as the dark matter candidate, the new interaction terms <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:msub><o:mi>y</o:mi><o:mi>χ</o:mi></o:msub><o:mi>ϕ</o:mi><o:mover accent="true"><o:msup><o:mi>χ</o:mi><o:mi>c</o:mi></o:msup><o:mo stretchy="true">¯</o:mo></o:mover><o:mi>χ</o:mi></o:math> and <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"><s:mi>μ</s:mi><s:msup><s:mi>ϕ</s:mi><s:mn>3</s:mn></s:msup><s:mo>/</s:mo><s:mn>2</s:mn></s:math> could induce various new production channels. For instance, when <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline"><u:msub><u:mi>m</u:mi><u:mi>ϕ</u:mi></u:msub><u:mo>></u:mo><u:mn>2</u:mn><u:msub><u:mi>m</u:mi><u:mi>χ</u:mi></u:msub></u:math>, the pair decay <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline"><w:mi>ϕ</w:mi><w:mo stretchy="false">→</w:mo><w:mi>χ</w:mi><w:mi>χ</w:mi></w:math> could be the dominant channel, rather than the delayed decay <z:math xmlns:z="http://www.w3.org/1998/Math/MathML" display="inline"><z:mi>ϕ</z:mi><z:mo stretchy="false">→</z:mo><z:mi>χ</z:mi><z:mi>ν</z:mi></z:math>. Another appealing scenario is when the dark sector is initially produced through the scattering process as <cb:math xmlns:cb="http://www.w3.org/1998/Math/MathML" display="inline"><cb:mi>N</cb:mi><cb:mi>N</cb:mi><cb:mo stretchy="false">→</cb:mo><cb:mi>χ</cb:mi><cb:mi>χ</cb:mi><cb:mo>,</cb:mo><cb:mi>N</cb:mi><cb:mi>N</cb:mi><cb:mo stretchy="false">→</cb:mo><cb:mi>ϕ</cb:mi><cb:mi>ϕ</cb:mi><cb:mo>,</cb:mo><cb:mi>h</cb:mi><cb:mi>ν</cb:mi><cb:mo stretchy="false">→</cb:mo><cb:mi>χ</cb:mi><cb:mi>ϕ</cb:mi></cb:math>, then the semiproduction processes <hb:math xmlns:hb="http://www.w3.org/1998/Math/MathML" display="inline"><hb:mi>N</hb:mi><hb:mi>χ</hb:mi><hb:mo stretchy="false">→</hb:mo><hb:mi>ϕ</hb:mi><hb:mi>ϕ</hb:mi><hb:mo>,</hb:mo><hb:mi>N</hb:mi><hb:mi>ϕ</hb:mi><hb:mo stretchy="false">→</hb:mo><hb:mi>ϕ</hb:mi><hb:mi>χ</hb:mi><hb:mo>,</hb:mo><hb:mi>N</hb:mi><hb:mi>χ</hb:mi><hb:mo stretchy="false">→</hb:mo><hb:mi>χ</hb:mi><hb:mi>χ</hb:mi></hb:math> could lead to the exponential growth of dark sector abundances. The phenomenology of the sterile neutrino and the cosmological impact of the dark scalar are also considered in the <mb:math xmlns:mb="http://www.w3.org/1998/Math/MathML" display="inline"><mb:msub><mb:mi>Z</mb:mi><mb:mn>3</mb:mn></mb:msub></mb:math> symmetric model. Published by the American Physical Society 2024