1. ST Occupancies (revisited) M. Needham EPFL

2. Introduction Occupancies matter Date rates/sizes In particular was data size on links from Tell1 to farm estimated correctly MC, normal running link loads ~ 50 % in hottest part of IT/TT Ghost rates in Tracker Key ingredient in getting ghost rate correct

3. Occupancies Data: Select Beam-Beam BxID Subtract beam gas crossings => Visible collisions MC: Gauss v38r0 (latest version) Min bias 1 interaction Velo opened correctly, 450 GeV L0 trigger 0x1209 (checked requiring 2 T tracks in detector gives same results) The same as can be December Analysis

4. Occupancies Occupancies made counting clusters To remove noise S/N cut at 5 (removes all ~ noise clusters) DetectorDefault S/N cut (MC) # noise clusters Default S/N cut (data) # noise clusters TT4.563.510 IT4.5643 Note use HEAD geometry (including Velo feature reported by Thomas ) Delta rays are on !

5. IT Occupancies Subtracting beam gas ~84 clusters per event in pp collisions MC expect 60 clusters per event IT1/IT3: 1.3 (MC) 1.15 (MC), IT2/IT3 1.16 (MC), 1.1 (data) Excess is 40 %: Parts of beam-pipe supports missing from MC ? Beam gas ~ 20 % hotter than collisions LHCb data preliminary LHCb data preliminary Collision BXID Beam gas BXID Magnet on Run 63690

6. TT Occupancies LHCb data preliminary Beam gas Collision Bx Subtracting beam gas ~ 100 clusters per event in collisions Data: ratio TTb/TTa 1.1, MC 1.2: secondaries produced upstream Beam gas ~ 10 % hotter than collisions Beam gas downstream of TT clearly seen… LHCb data preliminary Magnet on

7. Second Look Two worries: Beam Gas correction + Trigger New analysis Use run 63949 (70 k): lowered pt cut in HCAL trigger, least beam-gas Official MC sample with Velo @ 15 mm Study cuts to remove beam gas + symmetrize trigger bias data/MC BunchID selection as before # backward tracks # long and downstream tracks with pt > 500 MeV Position of primary vertex [if there is one] |z| < 15 cm

8. As Before ITTT Beam-gas Collision Beam-gas Collision After correction 84 clusters/event in beam-beam collision [As in December] After correction 103 clusters/event in beam-beam collision [As in December] Can see: fluctuations in beam gas dominate the tail Not so nice…. LHCb data preliminary LHCb data preliminary

9. New Example IT TT Beam-gas Collision Beam-gas Collision Cuts nicely kill all the beam-gas apart from those in the tail Not so nice…. Quote also MPV of distribution as estimator LHCb data preliminary LHCb data preliminary e.g 1 backward track + 1 Long or Downstream track, pt > 500 MeV

10. New Example e.g 1 backward track + 1 Long or Downstream track, pt > 500 MeV LHCb data preliminary LHCb data preliminary MC pp Collisions MC pp Collisions TTIT Comment: IT 1,2, 3 track peaks clearly seen (12, 24, 36 clusters) Defining a max in this case is ‘hard’ Rebinning + then max finding seems to give reasonable estimate

11. IT Summary ConditionsMax (Data)Max (MC)Mean (Data)Mean (MC) 1 high pt40258961 2 high pt48329565 1 high pt, 1 back44299163 1 high pt, 2 back48319363 2 high pt, 1 back50349766 2 high pt, 2 back54359866 PV, 1 backNot calc 8964 MPV+ Mean in data ~ 40 - 50 % higher than MC Or 15 clusters In terms of particles that is 1.3 particles/per event more High pt = Long or downstream track above 500 MeV

12. TT Summary ConditionsMax (Data)Max (MC)Mean (Data)Mean (MC) 1high pt694711668 2 high pt885713279 1 high pt, 1 back775112476 1 high pt, 2 back855313177 2 high pt, 1 back1006013982 2 high pt, 2 back1136314486 PV + 1 backNot calc 12093 MPV (Mean) ~ 40 (70) % higher than MC Or 26 clusters In terms of particles that is 6.5 particles/per event more

13. TT Summary e.g 1 backward track + 1 Long or Downstream track, pt > xxx MeV Stats… Scan pt cut and compare MPV data/MC

14. A glance at New MC MC pp Collisions MC pp Collisions LHCb data preliminary LHCb data preliminary No difference with the New MC.. Feature: new MC is softer ? Weaker constraint from PV requirement … Look with new MC, where where Velo-RICH region fixed 1 PV + backward track requirement

15. A glance at New MC Primary vertex + 1 backward + 2 long or downstream tracks pt > 500 MeV Closer to before…

16. A Glance at OT MPV + Mean in data ~ 40 - % too high Or 120 clusters In terms of particles that is 6.6 particles/per event more [assuming 20 hits per track] LHCb data preliminary MC pp Collisions OT Data Mean 660 MPV 460 MC Mean 450 MPV 330

17. A Glance at OT e.g 1 backward track + 1 Long or Downstream track, pt > xxx MeV

18. Summary Quoting mean in TT sensitive to tail in occupancy distribution …and beam gas correction Using MPV consistancy is found: 30 - 40 % effect in OT, IT TT Seems reasonably robust against selection criteria Beam gas now under control

19. Next steps Locate the missing material…. VELO, RICH, beam-pipe, RMS, BCMs, OT? Interesting to know how the occupancy in VELO, RICH, OT compares Known to be missing: pieces of beam-pipe 2-track vertex scan (M. De Cian) Thresholds ? Known no increase lowering Geant thresholds for electrons further Other parameters ?

20. Backup

21. IT Occupancies LHCb data preliminary LHCb data preliminary ADC What about the events with no beam ? Expect 2.8 clusters noise Some events also have an interaction Magnet on Run 63567

22. IT Occupancies LHCb data preliminary LHCb data preliminary IT3ASideX1 IT3TopX1 x MC Data IT1TopU Magnet on Run 63690 IT2BottomX2 Scale factor 1.4 applied to MC LHCb data preliminary LHCb data preliminary

23. IT Occupancies IT2BottomX2 Scale 1.7 IT2TopX2 Magnet off LHCb data preliminary LHCb data preliminary LHCb data preliminary LHCb data preliminary MC Data

24. IT Occupancies IT1ASideX1 Scale 1.7 IT3CSideU Magnet off LHCb data preliminary LHCb data preliminary LHCb data preliminary LHCb data preliminary MC does not know IT1A out from nominal Dead Noisy

25. IT Occupancies LHCb data preliminary LHCb data preliminary IT2CSideX2 IT2ASideV x MC Data IT3CSideU Dead Noisy Magnet on Run 63690 IT1CSideX1 Scale factor 1.4 applied to MC LHCb data preliminary LHCb data preliminary

26. TT Occupancies LHCb data preliminary LHCb data preliminary TTaXRegionA TTaXRegionB x MC Data TTaURegionB Magnet on Run 63690 TTbXRegionC Scale factor 1.6 applied to MC LHCb data preliminary LHCb data preliminary TT3 TT2 TT4

27. TT Occupancies LHCb data preliminary LHCb data preliminary TTbVRegionBTTbXRegionC x MC Data TTbURegionC Magnet on Run 63690 Scale factor 1.6 applied to MC LHCb data preliminary TT3 TT2 TT3 TT3 TT4

28. TT Occupancies LHCb data preliminary Beam gas Collision Bx Subtracting beam gas ~ 143 clusters per event in collisions ~ 10 noise/event clusters MC ~ 50 clusters per event…hmmmm Beam gas ~ 10 % hotter than collisions LHCb data preliminary Magnet off

29. IT Occupancies Subtracting beam gas ~ 170 clusters per event in collisions MC expect 103 clusters per event Excess is 65 %: Collars of beam-pipe supports missing from MC ? Beam gas ~ 26 % hotter than collisions LHCb data preliminary LHCb data preliminary CollisionBeam gas Magnet off