SEMINAR

In this seminar, I will discuss a few minimal setups for a light scalar dark matter (DM) having mass around a few hundred MeVs up to a few GeV and requiring light mediators to interact with the Standard Model (SM) particles. To avoid the strong constraints from CMB power spectrum observations, we focus on the Breit-Wigner resonance for DM annihilation channels, which can be either s-wave or p-wave, depending on the spin of the mediator. These lead to very different phenomenology as the velocity dependence of the annihilation cross-section is very different for the two cases in the recombination era, freezeout as well as in the galaxies. Moreover, relic density near resonance typically needs a tiny interaction between DM and the SM particles, which leads to the so-called early kinetic decoupling effect, considerably altering the parameter space near resonance. The interactions of the mediator can be constrained by various low-energy accelerator searches. On the other hand, the interactions of the DM are tested by indirect searches, which include the X-ray, cosmic ray, and gamma-ray observations, and also by the dedicated low-mass direct detection experiments. I will systematically discuss the current constraints and projected sensitivities in each category of the above probes. Lastly, I will briefly touch upon the challenges of computing the annihilation spectra for a MeV-GeV scale DM using the publicly available packages, because DM annihilates dominantly into hadrons in this mass range, giving rise to uncertainties involving hadronic form factors. I will conclude the seminar with an example of how the issues can be alleviated with micrOMEGAs 6.0 and the annihilation spectra could now be computed for a light scalar DM of mass 100 MeV and above.