time spread at epic dirc

Time spread of the photons as a function of polar angle.

  • 3-layer spherical lens with sapphire, r=[62,36] vs ideal lens
  • 32x32 pixels MCP-PMTs with HIQ400, CE=95%
  • pions 6 GeV/c; phi = 0 (no field); vertex y-shifted by 0.5*barwidth (to hit middle of the bar)
  • 0.5 mrad tracking
  • 100 ps time precision

Time spread for 99%, 95% and 90% of the photons in the event:

Example of time distribution at 90 deg:

Example of time distribution at 160 deg: