Update on Noise Analysis of the DHCal Test Beam at Fermilab

1. Update on Noise Analysis of the DHCal Test Beam at Fermilab Lei Xia

2. Outline • ‘Dead’ ASIC’s • Temperature monitoring of Apr – May run • Update on RPC noise • Update on correlated noise • Update on noise ‘hot’ spot CALICE collaboration meeting @ CERN

3. ‘Dead’ ASIC’s • We reported at the ALCPG’11 conference that a tiny fraction of the FE asic’s will not give any data in any run type • We identify them in noise runs • For Oct. and Jan. – Feb. runs, average fraction is only 0.27% • Things are more stable in Apr. – May run • For most part, we miss 16 asic’s (max 27, min 13) • This is only ~0.22% Max: 0.44% 16 missing ASIC’s (~0.22%) Apr.— May run Oct. and Jan.– Feb. runs CALICE collaboration meeting @ CERN

4. Noise monitoring • The DHCal prototype (1m3 and TCMT) is capable of setting the FE freely running • All FE signals are recorded, up to a certain rate limit (not likely to reach without beam) • Perfect running mode to measure noise in RPC • We use this running mode to monitor RPC noise during test beam • 2+ noise runs per day • Important data quality monitoring tool CALICE collaboration meeting @ CERN

5. Temperature/noise record for Oct. run Air conditioning fixed Air conditioning briefly down CALICE collaboration meeting @ CERN

6. Temperature/noise record for Jan.– Feb. run Gas flow reduced to 150cc/min, from 300cc/min CALICE collaboration meeting @ CERN

7. Temperature/noise record for Apr.– May run Didn’t run due to high T Portable AC in place CALICE collaboration meeting @ CERN

8. RPC noise estimate • Using the measured noise rate, we can estimate the expected noise level in triggered beam data • Assume all measured noise in self-triggered runs is from RPC itself (not exactly true) • Total number of channels in 1m3 + TCMT (52 layers) is 96x96x52 = 480K • Not including any possible correlated noise • Noise contribution to triggered beam events is extremely small (almost negligible), even when T is unusually high TCMT noise level, Apr.-May run 1m3 noise level, Apr.-May run Expected noise level for Oct. and Jan. runs Expected for a ‘cool’ DHCal stack CALICE collaboration meeting @ CERN

9. Update on correlated noise • By comparing self-triggered (trigger-less) noise data with randomly triggered noise data, we found correlated noise in the system • It is grounding related • Possibly behaving differently with/without trigger • May be different for noise/beam data? – need study • Relation to (different) beam condition? – need study • Careful study on-going • Define characteristics for correlated noise • Identify/eliminate correlated noise in beam data • Estimate the remaining correlated noise in data (if any) • Comparison between two data sets • Trigger-less vs randomly triggered • Green: two data sets show consistent noise level • Red: statistically inconsistent noise level, that suggests • Existence of correlated noise • Deferent behavior in different running conditions CALICE collaboration meeting @ CERN

10. Basic “features” of the correlated noise • Hits at RPC ground connector • Hits on the boarder of FE board • A lot of hits on one FE board (up to all 1536 pads) • Light-up single ASIC (all or almost all pads firing on one ASIC) Events from trigger-less noise run CALICE collaboration meeting @ CERN

11. Correlated noise with beam event: type 1 • Extra hits on RPC ground connectors • Easy to identify, easy to eliminate extra hits CALICE collaboration meeting @ CERN

12. Correlated noise with beam event: type 2 • A lot of extra hits in a few FE boards • Easy to identify, events can only be discarded CALICE collaboration meeting @ CERN

13. Correlated noise with beam event: type 3 • Extra hits on FEB boarders • Not easy to identify, events probably need to be discarded CALICE collaboration meeting @ CERN

14. Correlated noise with beam event: others • Type 4: events with ‘hot’ asic • Type 5: any combination of 1 – 4 • Study is on-going • Overall, it affects a very small fraction of the data sample (limits to be given) CALICE collaboration meeting @ CERN

15. Noise ‘hot’ spot • Noise ‘hot’ spots are seen in all three test beam periods • Nearly no visible effect on beam data (a little bit on multiplicity) • Varies with time, temperature, gas flow rate, etc. • NOT seen in the ‘cooler’ tail catcher • Believed to be related to insufficient glass surface cleaning • Showing up ONLY with elevated temperature CALICE collaboration meeting @ CERN

16. More evidence for T correlation: layer 14 Run 610294 Last noise run in Feb. run Two pronounced hot regions Run 610297 1st few noise runs in Apr. when stack is still cool Hot regions disappeared CALICE collaboration meeting @ CERN

17. More evidence for T correlation: layer 14 Run 650013 After stack reached stable temperature (pretty high) Hot regions came back and slightly worse Run 650029 Just started using portable air conditioning on 1m3 Hot regions shrank CALICE collaboration meeting @ CERN

18. More evidence for T correlation: layer 14 Run 650090 1m3 further cooled down Hot regions shrank further • Similar trend seen in other layers as well • Temperature is indeed the KEY factor here CALICE collaboration meeting @ CERN

19. Summary • Number of ‘dead’ asics is very small, and stable • RPC’s are in good shape after three beam tests • Average noise level is stable • Absolute noise level is lower due to improved cooling • RPC noise contribution to triggered beam data is extremely small (<0.1 hit/event) • RPC contribute negligible noise hits to beam data • Better understanding of correlated noise • However, more study is needed and in progress • Need to define its contribution to beam data • Noise ‘hot spots’ were due to unclean surface • Strong correlation with elevated T CALICE collaboration meeting @ CERN