Light Dirac neutrino portal dark matter with gauged U(1)B−L symmetry

We propose a gauged <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:mrow><a:mi>B</a:mi><a:mo>−</a:mo><a:mi>L</a:mi></a:mrow></a:msub></a:math> version of the light Dirac neutrino portal dark matter. 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:mrow><e:mi>B</e:mi><e:mo>−</e:mo><e:mi>L</e:mi></e:mrow></e:msub></e:math> symmetry provides a UV completion by naturally accommodating three right-handed neutrinos from anomaly cancellation requirements which, in combination with the left-handed neutrinos, form the sub-eV Dirac neutrinos after electroweak symmetry breaking. The particle content and the gauge charges are chosen in such a way that light neutrinos remain purely Dirac and dark matter, a gauge singlet Dirac fermion, remain stable. We consider both thermal and nonthermal production possibilities of dark matter and correlate the corresponding parameter space with the one within reach of future cosmic microwave background (CMB) experiments sensitive to enhanced relativistic degrees of freedom <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mi mathvariant="normal">Δ</i:mi><i:msub><i:mi>N</i:mi><i:mi>eff</i:mi></i:msub></i:math>. The interplay of dark matter, CMB, structure formation and other terrestrial constraints keep the scenario very predictive leading the <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:mi>U</l:mi><l:mo stretchy="false">(</l:mo><l:mn>1</l:mn><l:msub><l:mo stretchy="false">)</l:mo><l:mrow><l:mi>B</l:mi><l:mo>−</l:mo><l:mi>L</l:mi></l:mrow></l:msub></l:math> parameter space into tight corners. Published by the American Physical Society 2024