The contributions of the LAL group to the LAr data quality are based on the identification of noise in cells using the quality factor that compares the pulse shape to the expected pulse shape from a true energy deposit. The expected shape was taken from a prediction using the measured electronics components in the early Run-1 and is extracted from collision data in the late part of Run-1. In addition to individual noisy cells, several form of coherent noise as been identified as shown here:
This transient coherent noise is very short in duration and, once the « noise burst » is identified using the quality factor to flag noise, the data in a 50ms time window around the burst is declared bad. As an illustration, the following figure show the distribution of the fraction of cell above 3 sigma of the expected electronics noise in empty bunch crossing:
- black: no veto
- red: veto identified noise events
- cyan: after time window veto
The tail of the distribution is considerably reduced.
Contacts : Lydia Iconomidou-Fayard (staff), Nicolas Morange (staff), Christophe Goudet (PhD student), and some students.