Speaker
Description
We propose a novel particle physics framework that addresses multiple cosmological tensions and anomalies by incorporating self-interacting dark matter (SIDM) and dark radiation (DR) within an abelian gauge extension of the Standard Model. Our model features a $U(1)_D$ gauge symmetry that accommodates SIDM candidates which interact through the exchange of the $U(1)_D$ gauge boson. The velocity-dependent self-interactions of DM help alleviate the small-scale structure problems of the standard cosmological model.
Due to the presence of a light mediator and strong DM coupling, the thermal DM relic abundance is suppressed. To achieve the correct DM density, we consider a non-thermal production mechanism involving the decay of a long-lived scalar field that acts as a Pseudo-WIMP. This scalar decays to produce both DM and dark radiation. The DR produced from the scalar decay, occurring after Big Bang Nucleosynthesis but before recombination, can contribute a significant $\Delta N_{\rm eff}$ that may help resolve the Hubble tension. The DR component can be probed by future cosmic microwave background (CMB) experiments. The gauge kinetic mixing and scalar portal interactions between the visible and dark sectors make this scenario testable at various dark photon search experiments, as well as DM direct and indirect detection experiments.
| Field of contribution | Phenomenology |
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