1. An offline look at TIF data David Stuart UC Santa Barbara May 2, 2007

2. 2 Introduction Last week I volunteered to look at data offline. I want to describe what I have done since. I’ve looked at two issues: –Comparing VR and ZS (motivated by discussions with Slawek). –Studying the Multi-Hit events (motivated by discussions with Patrizia et al). I am using a non-standard tool: –I use CMSSW to dump the raw data and then feed it to standalone-code. It is easier for me to use, since it is my old CDF code. –My code looks at all events in a single module (rather than all modules in a single event). That makes some things easier and some things harder. This different approach may complement other studies. David Stuart, UCSB, May 2, 2007

3. 3 Compare Virgin Raw and ZeroSuppressed Ped run VR cosmics ZS cosmics ADC - PED Comparing Ped, VR and ZS for one sample module. Very small differences between ped and cosmics. David Stuart, UCSB, May 2, 2007

4. 4 ADC - PED Low charge region not properly normalized. My noise calculation may be different. It might be shoulder strips from hits. I’ll look at low multiplicity modules; ZS peds might help. Possible shape difference in signal region. More apparent in some modules than others. To be investigated. Compare Virgin Raw and ZeroSuppressed Simulating ZS gives qualitative agreement, but there is a quantitative difference that is still to be understood. David Stuart, UCSB, May 2, 2007

5. 5 Clusters Cluster charge Use thresholds of: 6*noise for 1 strip 4*noise for >=2 strip Huge signal to noise. Thresholds could be tightened, but noise hits not significant. Odd spikes… TIB TOB Looked at clusters in ZS Run 6505. David Stuart, UCSB, May 2, 2007

6. 6 Cluster Spikes? The TIB spikes at 250, 380, and 4000 (off the plot) are all from one module, detector id 369264142. That module has an odd region as shown here. Those channels are at their pedestals. Virgin raw data looks fine. It gives normal hits otherwise. Maybe the Zero Suppression is failing there? Problem also present in Run6509. Will check other runs… David Stuart, UCSB, May 2, 2007

7. 7 TOB spike at 254 and 508 appears in many modules, e.g., below. No specific position. Investigating… Cluster Spikes? David Stuart, UCSB, May 2, 2007

8. 8 High Multiplicity Events Try to understand these high multiplicity events. Are they cosmic showers or evidence of a problem? David Stuart, UCSB, May 2, 2007

9. 9 Possible hypotheses: Noise Multiple events being merged in the DAQ Multiple events being merged in the offline Cosmic showers Something else? An interesting mystery. Hopefully we’ll have a related one next year… High Multiplicity Events David Stuart, UCSB, May 2, 2007

10. 10 High Multiplicity Events They appear to be following a steep spectrum. No evidence of specific structure. David Stuart, UCSB, May 2, 2007

11. 11 High Multiplicity Events They contain normal looking hits that are apparently from tracks. So, not noise. Maybe many events getting overlain… David Stuart, UCSB, May 2, 2007

12. 12 To see if events were being overlaid in the offline, Vitaliano suggested comparing the number of clusters to the event size in the StorageManager file. Used code provided by Kristian Hahn to dump the data and plot the event size. Correlation indicates that a purely offline overlay is not the culprit. Maybe the DAQ? (Number of clusters)/100 (EventSize/1000)-53 ? High Multiplicity Events David Stuart, UCSB, May 2, 2007

13. 13 Multi-hit events First, I checked a few things about the clusters: Cluster charge looks same. Cluster position looks same. Cluster length distribution “similar”. Events appear to have tracks. Run 6507, Event 14907 David Stuart, UCSB, May 2, 2007

14. 14 If events where being overlaid, not only would be see many hit clusters, we’d also see many “noise clusters”, I.e., channels that just randomly pass the zero suppression. Are there more of those in the busy events? Check this by looking at strip pairs with (ADC-PED)/Noise between 2 and 3, requiring no latched channels within 2 strips on either side to suppress. Hit cluster Noise cluster High Multiplicity Events David Stuart, UCSB, May 2, 2007

15. 15 The noise clusters are uniform with event number, indicating no overlays. First events are noisy. High Multiplicity Events David Stuart, UCSB, May 2, 2007

16. 16 High Multiplicity Events Andrea Venturi pointed out that if they are cosmic showers, then they should contain particles that do not hit the trigger scintillators. It is hard to discern the tracks, but the hit distribution should suffice. The rare hits in the lower left don’t seem to be in the trigger acceptance. Are those hits only present in the high multiplicity events? David Stuart, UCSB, May 2, 2007

17. 17 High Multiplicity Events Andrea Venturi pointed out that if they are cosmic showers, then they should contain particles that do not hit the trigger scintillators. It is hard to discern the tracks, but the hit distribution should suffice. The rare hits in the lower left don’t seem to be in the trigger acceptance. Are those hits only present in the high multiplicity events? Yes. David Stuart, UCSB, May 2, 2007

18. 18 High Multiplicity Events Andrea Venturi pointed out that if they are cosmic showers, then they should contain particles that do not hit the trigger scintillators. It is hard to discern the tracks, but the hit distribution should suffice. The rare hits in the lower left don’t seem to be in the trigger acceptance. Are those hits only present in the high multiplicity events? They are outside the luminous region for single track events. So, they look like showers. Yes. David Stuart, UCSB, May 2, 2007

19. 19 Summary I’m comparing virgin raw and zero suppressed. Makes sense to 1st order. More investigation needed to understand in detail. I started looking at clusters At least one anomaly might be a ZS problem. Looked at multi-hit events Not consistent with DAQ or offline overlaying events Consistent with cosmic showers One interesting next check is dE/dx. Do these showers have higher dE/dx, which would reveal very low momentum tracks? Andrea Giammanco is interested in applying his dE/dx. Next: Understand ZS better. Look at more recent runs. Look at tracks. Other? Details at http://hepdhcpd.physics.ucsb.edu/cgi-bin/lgbk?user=stuart&ent=19794 David Stuart, UCSB, May 2, 2007