EFT origin of secluded dark matter

The present study aims to unveil a scenario with a nonminimal secluded dark sector (DS) in an effective field theory (EFT) framework. To explore this, we have examined a suitable extension of the type-X two Higgs doublet model (2HDM) as a potential origin for the secluded DS. The DS comprises a dark matter (DM) candidate and a mediator particle “ <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mi>a</a:mi> </a:mrow> </a:math> ” and possesses some nonminimal characteristics. It becomes nonthermally populated through diverse dim-6 four-Fermi operators, effectively generated by integrating out the heavier Higgs particles. The analysis further focuses on the consequences of the collision processes <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mrow> <c:mi>DM</c:mi> <c:mo>+</c:mo> <c:mi>a</c:mi> <c:mo stretchy="false">↔</c:mo> <c:mi>a</c:mi> <c:mo>+</c:mo> <c:mi>a</c:mi> </c:mrow> </c:math> and <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"> <f:mrow> <f:mi>DM</f:mi> <f:mo>+</f:mo> <f:mi>DM</f:mi> <f:mo stretchy="false">↔</f:mo> <f:mi>a</f:mi> <f:mo>+</f:mo> <f:mi>a</f:mi> </f:mrow> </f:math> occurring within the DS. We have investigated the significance of employing an EFT approach in tracking the temperature evolution of the DS. Within the present framework, the observed relic abundance of the DM can be realized through both dark freeze-out and freeze-in mechanisms. Further, we have delineated the permissible ranges of the relevant parameters, viz., the DM mass ( <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:msub> <i:mi>m</i:mi> <i:mi>χ</i:mi> </i:msub> <i:mo>≳</i:mo> <i:mn>20</i:mn> <i:mtext> </i:mtext> <i:mtext> </i:mtext> <i:mi>GeV</i:mi> </i:math> ), the portal coupling ( <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"> <k:msub> <k:mi>C</k:mi> <k:mi>τ</k:mi> </k:msub> <k:mo>≲</k:mo> <k:msup> <k:mn>10</k:mn> <k:mrow> <k:mo>−</k:mo> <k:mn>14</k:mn> </k:mrow> </k:msup> <k:mtext> </k:mtext> <k:mtext> </k:mtext> <k:msup> <k:mrow> <k:mi>GeV</k:mi> </k:mrow> <k:mrow> <k:mo>−</k:mo> <k:mn>2</k:mn> </k:mrow> </k:msup> </k:math> ), and the DS coupling ( <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"> <m:mi>λ</m:mi> <m:mo>≲</m:mo> <m:msup> <m:mn>10</m:mn> <m:mrow> <m:mo>−</m:mo> <m:mn>6</m:mn> </m:mrow> </m:msup> <m:mtext> </m:mtext> <m:mtext> </m:mtext> <m:msup> <m:mrow> <m:mi>GeV</m:mi> </m:mrow> <m:mrow> <m:mo>−</m:mo> <m:mn>2</m:mn> </m:mrow> </m:msup> </m:math> ), by taking into account the perturbativity of the involved couplings while reproducing the observed DM relic and complying with the bounds from successful big bang nucleosynthesis (BBN) and <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"> <o:mi>γ</o:mi> </o:math> -ray searches.