In a post-pandemic era, this hybrid workshop brought about valuable on-site discussions between different groups local to Hamburg and exchanging knowledge with international experts through zoom attendance.
Accelerator physicists from the University of Hamburg and DESY exchanged information with photon scientists or laser physicists. The workshop included seven main talks by members from different groups actively contributing to the simulation studies for FLASH2020+ and several discussion sessions. Furthermore, two main hands-on sessions gave a reasonably comprehensive overview of how we simulate the interaction of a realistic electron beam with realistic laser beams in Seeded FEL simulations. Overall, the workshop successfully achieved its goal of bridging several discussion gaps between members of both machine (M) and photon science (FS) divisions. It also initiated the discussion for the next chapter of start-to-end simulations for THz experiments and novel or advanced seeding setups. Further cooperation between University and DESY FS and M groups is planned in three areas: writing a paper summarizing the start-to-end simulations efforts, THz Simulations, and advanced modes of operation for FLASH2020+. In addition, the 4th FLASH2020+ Start to End Simulation Workshop is planned for June 2023