|Ring Imaging Cherenkov Counter|
|R I T E R|
|Iterative algorithm for the analysis of the Cherenkov rings|
Identify reconstructed tracks as one of the particle : electron, muon,
pion, kaon or proton.
|Usage in the analysis:|
For the time being, there is more than one method used for particle identification in the RICH detector. Therefore RICH likelihoods are copied to the parallel RTRI table and the entries in the table RTRA are reset to -1. Therefore one should use one of the special functions, which are implemented to copy the corresponding fields in RTRI back to RTRA or to combine them in the unified likelihood. The later method suffers from the unknown efficiency vs. misidentification relation.
The following function should be used to copy likelihoods calculated wit one method back to the appropriate places.
|int copyRTRItoRTRA(int algorithm); // algorithm = 1 for RITER or =0 for RISE|
This function should be called after the reconstruction in the
Note that if you omit HITB in the last command, there will be also RICH standalone package RISE running, which is not needed by RITER, but it consumes a lot of CPU-time!!!
Make sure to include appropriate kuip commands for the track reconstruction in your ARTE kumac and that refit is on, e.g:
To run the iterative analysis during the reconstruction include the following kuip commands:
Particle identification module RITER needs as an input:
During the reconstruction, the following field in the table of the reconstructed tracks RTRA are filled.
|rtra->flr & 0xff||RITER particle identification flag : If greater than 0, a track is within geometrical acceptance of the RICH|
|rtra->lre||likelihood of electron hypothesis|
|rtra->lrmu||likelihood of muon hypothesis|
|rtra->lrpi||likelihood of pion hypothesis|
|rtra->lrk||likelihood of kaon hypothesis|
|rtra->lrp||likelihood of proton hypothesis|
|rtra->lrme||likelihood for multi electron hypothesis|
|background = 1- (lre+lrmu+lrpi+lrk+lrp)||likelihood for hypothesis that the distribution of photons around track is consistent with backrgound|
The iterative method is based on the assumption that most of the RICH detector hits, which represent a background in the Cherenkova angle histogram, originate from other tracks within the saame event. An iterative procedure is used to clear such histograms. A weight is assigned to each Cherenkov photon hit - track pair. After the iterations, the photon hit has the highest weight for the track, where represents the signal and lowest where it is part of the background.
The weigted photon hits are used for the calculation of likelihood functions for different hypotheses.
The method is described in more detail in
Invariant mass distribution for decay of Phi to two Kaons. Different RICH likelihood cuts are applied in the selection of track pairs