1. NSW background studies Max Bellomo, Nektarios Benekos, Niels van Eldik, Andrew Haas, Peter Kluit, Jochen Meyer, Felix Rauscher 1

2. Introduction 2 Summary of the results for three background studies: 1.Overlay method 2.Injection method 3.Full pile up NSW simulation

3. NSW background modeling: overlay Max Bellomo, Niels van Eldik, Andrew Haas, Jochen Meyer, Peter Kluit Muons NSW 25 April, Simulation PP 22 April Muon NSW 18 April 3

4. Overlay modeling 4 Details have been presented in the Simulation PP meeting https://indico.cern.ch/conferenceDisplay.py?confId=247906 Slides 5-7: TDR plot for EI occupancy @ 2.6e34 cm-2s-1 Contains now 100 events with each 10 events overlaid. Backup material for the method: Slides 809 Cross check Data-Data 2012: overlay of 3 times for run 206573 vs run 205010. Overlay of 3 times for run 206573 and comparison to run 205010 shows that on average the clusters multiplicities in the Inner wheel agree at the 20% level. Slides 10-13 Other cross check plots: -Validation of the EM and EO rate with the overlay @ 5% - Limitations of the present software: CSC are a factor 1.4 too high

5. MDT EI occupancy: saturation and non-linearity 5 Occupancy is the number of times a tube fires per event For the overlay data (Zero Bias) is used.

6. TDR text 6 caption: a) The occupancy vs the MDT tube number for the EI chamber for Overlay data (black) and Zero Bias data scale up by a factor 10. b) The ratio of the Overlay to Zero Bias (x 10) occupancy vs MDT tube number. A study has been performed overlaying events to determine the impact on the current EI detector. The overlay method is described in detail ATL-SOFT-SLIDE-2012-188. Here 10 Zero Bias events are overlaid to produce 1 event. The Zero Bias events have been collected in 2012 with a dedicated trigger. The instantanuous luminosity corresponded to 2.6e33 cm-2s-1. The overlayed events correspond to the background one would expect for a luminosity of 2.6e34 cm-2s-1.

7. TDR text 7 The results for this study are shown in Figure ~xxxx. Only the EI MDT chambers closest to the beamline were selected. The black curve corresponds to the Zero bias occupancy in these chambers detector averaged over the sectors and the two endcaps scaled up by a factor of 10. The red curve the result of the overlay with 10 Zero bias events. One can observe - in particular in the ratio plot - that the red curve does not scale to the black curve at high occupancies. At high tube nrs and low occupancies below 20% it does scale. This effect is due to the fact that at high occupancy MDT hits get masked: the total number of hits will not scale linearly with the background level and saturation takes place. This saturation effect that will lead to MDT hit efficiency losses is one of the reasons to replace the EI MDTs by the proposed NSW.

8. Data-Data 2012 cross check 8

9. 9 Overlay of 3 times for run 206573 and comparison to run 205010 shows that on average the clusters multiplicities in the Inner wheel agree at the 20% level. The scale factor for the MDT = 1.22 the TGC 1.27 and the CSC 0.97. The numbers are dominated by systematic errors that are at the level of 20%.

10. MDT EM occupancy: 10 Occupancy is the number of times a tube fires per event Here –as expected - no saturation is observed. The ratio should go to 1-occupancy = 0.85. This is indeed observed

11. MDT EO occupancy: 11 Here –as expected - no saturation is observed. The ratio should go to 1-occupancy = 0.95. This is indeed observed. Conclusion: Overlay method in MDT Endcaps is OK at the 5% level.

12. CSC phi occupancy: 12 Here a discrepancy is found: the overlay produces a 40% too much background.

13. CSC eta occupancy: 13 Conclusion: Overlay method for the CSC produces about 40% too much background in eta and phi.

14. NSW background modeling: hits and segment Injection Niels van Eldik, Peter Kluit, Felix Rauscher Muon NSW 26 April 2013 e.g. 14

15. Introduction 15 Method: use the injection of hits segments in the Inner wheel for the estimation of the background This is done in three steps: 1) Validate and parametrize the hits and segments MDTs and TGCs in the Inner wheel using the high mu single bunch run. No out of time pile up is present here. Sim hits are produced and run though the standard digitization and analyzed. 2) Apply time wrapping +- 40 BCs to these hits and segments and compare this to the backgrounds in the Z mumu period D data. This is a crucial test of the injection method. Note that the Z data doesnot only contain pile up but also cavern background. 3) Simulate these hits and segments in the NSW detectors using a 25 nsec bunch spacing. The generated Sim hits are run through the fast digitization for the NSW detectors and analyzed.

16. Cross checks step 1 TGC clusters 16 Note the target for Data/MC is 0.5 Because only 1 endcap is simulated In step 2 the TGC will increased by a factor of 3

17. Cross checks step 1 MDT clusters / TGC confirmed 17 In step 2 the TGC will increased by a factor of 3

18. Cross checks step 1 MDT segment clusters 18 Conclusions: reasonable description of the in time pile up in the MDTs and TGCs both for high and low cluster multiplicities. A more quantitative statement will be given at the next step.

19. Cross checks step II TGC clusters 19 Note the target for Data/MC is 0.5 Because only 1 endcap is simulated Here time wrapping +- 40 BC is applied and the “SimInjection” data is compared to the Z data that includes pile up and cavern background TGC rate is 0.39/0.5 = 0.78

20. Cross checks step 1I MDT clusters / TGC confirmed 20 MDT cluster rate is too low: 0.148/0.5 = 0.30

21. Cross checks step 1I MDT segment clusters 21 Cluster segment rate is too low by a factor: 0.443/0.5 = 0.88

22. Conclusions from step 1-2 22 The injection method: works reasonably The step 2 test shows that: TGC injected clusters are OK at the 20% level MDT injected segments rates are OK at the 20% level However the MDT clusters rate are about a factor 3 too low This could be due to the presence of cavern background

23. NSW background modeling: Simulations Pile up vs Injection Nektarios Benekos, Niels van Eldik, Peter Kluit, Felix Rauscher Muon NSW 12 May 2013 23

24. Introduction 24 The results of two NSW simulations will be compared. 1)Full pile up simulation chain with new NSW detectors and fast digitisation. The sample was generated by Nektarios: sLHC, pileups ~120 to 140 with 25ns bunch spacing /eos/atlas/user/n/nectar/NSW/PileUpProduction_sLHC/MC12.107209.Parti cleGenerator_dimu_Pt10_100.atlasG4.0001/ See also: https://indico.cern.ch/getFile.py/access?contribId=7&resId=0&mat erialId=slides&confId=248974 https://indico.cern.ch/getFile.py/access?contribId=7&resId=0&mat erialId=slides&confId=248974 This corresponds – my calculation - to a luminosity of 3e34 cm- 2s-1. In the plots sample 1) is scaled to a luminosity of 2.6e34 cm-2s-1.

25. Introduction 25 The second sample is: 2) The hit and segment Injection method. Background hits and segments are added in the Inner wheel using a 25 nsec bunch spacing. The injected background is increased by a factor of 10 (wrt the 2012 period D data), it corresponds a luminosity of 2.6e34 cm-2s-1. The samples was produced by Felix. wget http://pcphmpi00/NSW_production/download_all.sh [pcphmpi00] bash download_all.sh NOTE: this works only in the CERN network. The files with 1x the background are digi_rt1_evt*.nSW_DigitizationOutput.pool.root ant the ones with 10x the background are digi_rt01_evt*.nSW_DigitizationOutput.pool.root In both cases the generated Sim hits are run through the fast digitization for the NSW detectors and analyzed. In the fast digitization the energy thresholds for the sTgc and MicroMegas were put to the value of 1 MeV.

26. Comparison PileUp vs Injection MDT and MicroMegas 26 NSW layout EI MDTs: the |eta|>2 chambers on the Inner wheel The MDTs and CSC near beamline are replaced by MM and sTgc

27. Comparison PileUp vs Injection sTGCs 27

28. Occupancy PileUp 28 STgc only for current BC MM assumes four strips firing per gasgap

29. Occupancy Injection 29 Odd shape for MicroMegas Bug that shifts the strip nr for odd/even chambers

30. Conclusions 30 Results for two methods for the occupancy of the NSW Detectors. The injection method predicts rates that are about 30% to 60% higher than the Full Sim. Maximum occupancy @ luminosity of 2.6e34 cm-2s-1: Micromegas 4% sTGC pads 1% sTGC strips 0.4% sTGC wires 0.8% The systematic uncertainty on these numbers is rather large because – mainly because they should include cavern background and the singles that are difficult to predict. A safety factor 3-4 is probably reasonable (see also slide 22). These numbers could be quoted in the TDR. Both the Pile Up and the Injection samples can be used for e.g. NSW segment or track reconstruction studies in a high background environment.