LHC Run 2 is uncharted territory. The unprecedented 13 TeV centre-of-mass energy and high luminosities present a fantastic opportunity to discover new physics arising from dark or hidden sector models and an unique opportunity to unveil new boundaries in our understanding of nature. There is a rich program in the ATLAS experiment of searches for dark photons, hidden valley pions, exotic decay channels of the Higgs boson and many other exotic hidden signatures from the dark sectors.

The aim of this workshop is to bring together experts from the theoretical and the ATLAS experimental communities in various aspects of hidden sector physics for a joint brainstorming on the status of this research, identify areas for common efforts and improvements and set new promising directions. The present status of the analyses will be reviewed with the idea to unify the search strategies and tools.
The first day is an open day session in which everybody can participate and contribute with ideas, comments and suggestions.