5.2.2 Endcap Detector Algorithm

In the proportional chambers a trigger track candidate is recognized every time at least four out of six precise coordinate hits (strips) in a module align along a straight line. Timing is very bad in this projection, but the timing of the associated coarse coordinates (wires) is instead quite good, owing to the relatively short drift time (~40ns) and the planes staggering. In particular the first and the second hit on the wires associated to a track in the j projection will certainly be within the 25ns interbunch time. The second hit gives a better tag, since there is a lower probability that it is due to a spurious interaction.

Figure 15 shows the time of the second hit as measured on a beam test of a chamber prototype and proves that it can safely tag the parent bunch crossing [4].

Figure 15: Time of the second wire hit associated to a trigger track candidate in the precise coordinate plane.