Time-of-Flight Counters, TOF

A time-of-flight (TOF) detector system using plastic scintillation counters is very powerful for particle identification in $e^+e^-$ collider detectors. For a 1.2 m flight path, the TOF system with 100 ps time resolution is effective for particle momenta below about 1.2 GeV/c, which encompasses 90 % of the particles produced in $\Upsilon$(4S) decays. It can provide clean and efficient $b$-flavor tagging.
In addition to particle identification, the TOF counters provide fast timing signals for the trigger system to generate gate signals for ADCs and stop signals for TDCs. To avoid pile-up in the trigger queue, the rate of the TOF trigger signals must be kept below 70 kHz. The gate and stop timing for the CsI calorimeter and CDC sets a time jitter requirement of less than $\pm$10 ns. Simulation studies indicate that to keep the fast trigger rate below 70 kHz in any beam background conditions, the TOF counters should be augmented by thin trigger scintillation counters (TSC) [4,6].