Fitting Dark Matter in the Standard Model of elementary particles is one of the most prominent open questions of contemporary physics. Null results in direct detection experiments of galactic halo DM and in high-energy accelerator searches at the LHC call for an alternative explanation to the current WIMP paradigm. Light dark matter is the new compelling hypothesis that identifies dark matter with new sub-GeV “Hidden Sector” states, neutral under Standard Model interactions and interfacing with our world through a new force. The simplest model predicts sub-GeV light dark matter particles, charged under a new force in Nature and interacting with the SM particles via the exchange of a light spin-1 boson, usually referred to as ``heavy photon” or ``dark photon”.
In the last few years a broad experimental program started to explore this new scenario, searching both for light dark matter and for the new force mediator. In the seminar, after introducing the light dark matter physics case, I’ll review the most important experimental results in the field and present current and future initiatives. I’ll specifically discuss the recently-reported anomalies observed in nuclear transitions on 8Be and 4He, and their possible explanation as the existence of a new 17 MeV particle, mediator of a new protophobic force.