WG2 comprises all Cherenkov-based and TOF detectors employed for particle identification, such as RICH, DIRC, TOF, TOP, TORCH, plus any new concepts. The participation of the groups is motivated by the following interests:

• study of advanced PID techniques.
• developing new compact RICH concepts.
• optimal operation of new detectors.
• future DIRC detector applications.
• development of innovative RICH configurations, like pressurized argon RICH (e.g. ePIC at EIC), Aerogel-based RICH (e.g., RICH-0 in AMBER at CERN), lightweight RICH for a Higgs Factory.
• study the impact of time-resolved readout for future RICH detectors.

The work in WG4.2 focuses on new and improved detector concepts, achievable performance, and intrinsic limitations. Often, the studies will be based on Monte Carlo codes and analytical calculations.