Efficiency definition
For a given track, determine how many HOTs (hits-on-track) it should have based on its trajectory.
If 4 HOTs are expected, but only 3 are found, find which strips the 4th one was supposed to involve and see if they are in the list of the available Svt clusters.
Define the probability esp.pt to have a space point as
ez = probability to find a Z hit
ef = probability to find a Phi hit
ecomb = probability to combine them