2 passes allows fit of data with realistic model
The 2D pixel pattern of a hit is determined by 5 parameters
5 parameters/hit is a lot to vary, especially for clusters with many (ɯ) peaks in them.
ř Would be best to know crossing angles a and l for efficient fit of model to data
Hitfitting pass after tracking used to perform fit efficiently
- mode 5: vary all 5 hit parameters, with trackerís a and l as initial guess
- mode 6: vary only position and amplitude,
with trackerís a and l fixed