Informal High Energy Theory Seminar

Light new particles with masses well below the GeV-scale are an often considered and plausible extension of the Standard Model. In this talk I will present new results on dark photons, a massive vector boson kinetically mixed with the photon. The model serves as a prototype scenario for energy injection in the early Universe and we will use it to survey more recent developments in Big Bang Nucleosynthesis which includes a new solution to the cosmological lithium problem. If dark photons have masses below 10 keV they will also be emitted from the interior of stars. In a second part of the talk, we identify a new stellar energy loss mechanism originating from a resonant production of dark photons. Compared to previous analyses, limits on dark photons are significantly improved, to the extent that many dedicated experimental searches now find themselves deep inside astrophysically excluded regions. In a final part of the talk, we demonstrate that constraints on the atomic ionization rate imposed by the results of the XENON10 experiment make low-threshold Dark Matter experiments the most sensitive dark vector helioscopes, surpassing even the most stringent astrophysical and cosmological limits.