Z4 symmetric inverse seesaw model for neutrino masses and FIMP dark matter

A theoretical framework based on a spontaneously broken <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msub><a:mi>Z</a:mi><a:mn>4</a:mn></a:msub></a:math> symmetry is proposed to simultaneously explain neutrino mass generation via the inverse seesaw mechanism and dark matter (DM) production through a freeze-in scenario. This work extends the standard model with right-handed neutrinos <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:msub><c:mi>N</c:mi><c:mi>i</c:mi></c:msub></c:math>, additional fermions <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:msub><e:mi>χ</e:mi><e:mi>i</e:mi></e:msub></e:math>, and a complex scalar <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi>S</g:mi></g:math>. An unbroken <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:msub><i:mi>Z</i:mi><i:mn>2</i:mn></i:msub></i:math> subgroup ensures the stability of the DM candidate, whose relic abundance is dominantly produced via decay and scattering processes involving heavy singlet fermions. Phenomenological analyses show that this relatively minimal construction accommodates the observed neutrino oscillation parameters, consistent with the latest global fit data. Furthermore, the model successfully reproduces the observed DM relic density within the parameter space relevant to neutrino phenomenology, establishing a connection between neutrino properties and DM production.