DA code
Noisy pixel search
The noisy pixel search is always based on one run only. There is a minimum number of events required to do the search - fMinEventsForNoisy. The search is basically performed on the level of one read-out chip (8192 pixels). The hits in each pixel is compared to:
- fixed limit ratio - fDefinitelyNoisyRatio. If a pixel fires more than this ratio, it is noisy
- binomial with hit-probability p = NChipsHits/8192/Nevents. A limit is set so that the probability of falsely declaring a noisy pixel is less than MistakeProbabilityNoisy for the complete search on the full detector
The parameters in italic are defined in the file physics_params.txt
PARAMETER |
DESCRIPTION |
| fMinEventsForNoisy | Minimum number of events required for noisy search |
| fDefinitelyNoisyRatio | Fraction of events a pixel has to fire to be declared noisy |
| MistakeProbabilityNoisy | Probability to falsely declare one noisy pixel (out of all) for this search |
Dead pixels search
The dead pixel search may span several runs, in order to collect more statistics. There is a minimum number of events required to even try to perform the search - fMinEventsForDead. The search requires that a noisy pixel search has been done first. The noisy pixels are then removed from the hit-maps before the dead pixel search. Also the dead search is basically performed on the level of one read-out chip. Each chip will be put in one of the following four categories:
- ENOUGHSTAT: all 8192 pixels have at least one hit OR probability of falsely declaring a dead pixel is less than MistakeProbabilityDead for the complete search on the full detector
- DEAD: no hits at all in the chip AND NEqHits > fMinNrEqHitsForDeadChips, where NEqHits is the number of hits for the full DDL (60 chips)
- INEFFICIENT: a chip is called inefficient when NChipHits < NEqHits/60*fRatioToMeanForInefficientChip
- NEEDSMORESTAT: all other cases than the three above
If there are no chips in the category NEEDSMORESTAT, the calibration is complete, and the so-far temporary dead reference files will be sent to FXS. After the run, the hit-maps are reset and the dead search restarted.
Dead pixels will be declared for the ENOUGHSTAT and DEAD chips, while the INEFFICIENT ones will just be left out.
Even if the calibration was not complete, the dead pixels will be sent to FXS. If the calibration was not complete, the lists may later be updated for the current run.
A local copy of the dead pixel list is kept as a starting point for the next calibration. The first step in the next search will be to loop through all previously found dead pixels, and see if they still have no hits.
The parameters in italic are defined in the file physics_params.txt
PARAMETER |
DESCRIPTION |
| fMinEventsForDead | Minimum number of events required for dead search |
| MistakeProbabilityDead | Probability to falsely declare one dead pixel (out of all) for this search |
| fMinNrEqHitsForDeadChips | Minimum number of hits in one DDL required to be able to declare a fully dead chip |
| fRatioToMeanForInefficientChip | If a chip has less hits than this fraction of the mean number of hits for all chips on the DDL, it is declared inefficient |
Preprocessor code
- Standalone Noise Scan: noisy list from online scan is put in OCDB with run validity from current run until infinity
- Physics Noisy Pixel Search: reads noisy pixels from OCDB. Noisy pixels sent from the online calibration is added to the previous list. Noisy list is put in OCDB with run validity for current run only
- Physics Dead Pixel Search: dead list from online calibration is put in OCDB with run validity for current run only