1. Calculation of the Common Noise Paolo Zuccon

2. CN Algorithms DSP_orig: The algorithm implemented in the DSP take the mean of the good (Status==0) VA channels up to max 32 channels. There is no requirement on a min number of channels to calculate the mean DSP_64: As DSP_orig except the search for good channels accepts up to 64 channels. High: Take the mean of the channels in the VA which are good (Status==0) and are within § 10  RAW. A further check is done to have at least 10 channels to calculate the mean. Median: Take the median value of the 64 channels. This kind of algorithm is widely used in digital signal processing, to eliminate “peaked noise” from audio (scratches) and video signals.

3. CN on protons S VA on beamS VA off beam K VA on beamK VA off beam Legend: DSP_Orig High Median

4. CN on Z>1 S VA on beamS VA off beam K VA on beamK VA off beamLegend: DSP_Orig DSP_64 High Median

5. Correlation Z>1 Median DSP_Orig High S VA on beam K VA on beam

6. Absolute Difference DSP_Orig - MedianHigh - Median DSP_Orig - MedianHigh - Median S-Side K-Side 0.04% Outside -5 ¥ +15 0.03% Outside -5 ¥ +15

7. Legend: DSP_Orig DSP_64 High Median

8. Legend: DSP_Orig DSP_64 High Median

9. Legend: DSP_Orig DSP_64 High Median

10. The High algorithm may fail if a big undershoot happen so all the channels are outside § 10  RAW In run 248 this happen for the 0.1% of events, the failure rate of High algo must be calculate with cleaner samples. Legend: DSP_Orig DSP_64 High Median

11. Example of High algo failure

13. Median can fail to! But what to do with such an event ?

14. Conclusions  DSP_Orig algorithm introduce some bias that can worsen the charge resolution  The High algorithm appear to be acceptable from the point of view of computing time and fair enough with the high charges  Care must be taken to handle the cases where the High algo fails to correctly handle the highest charges. (dump the entire VA)