1. Monte Carlo Tuning and Beam Test Comparisons Toru Iijima Nagoya University 2013.12.6 Belle II TOP Mini-Review 2013/11/30Belle II TOP Mini Review 1

2. Outline Purpose of this talk 1.Summarize all of the details put in MC to get to match data 2.Summarize MC-data comparisons 2013/11/30Belle II TOP Mini Review 2 Proof of quartz optics BPAC focused review summary report (21 October, 2013) Main contributors to this presentation: Matthew Barrett, Michael Jones, Brian Kirby (Hawaii), Jeter Hall (PNNL), Marko Staric (Ljubljana), Kenji Inami, Yuhei Ito, Kodai Matsuoka (Nagoya).

3. Beam Test Setup 2013/11/30Belle II TOP Mini Review 3

4. Measured Items 1.cos  = 0 (beam normal to the quartz bar) 2.cos  = 0.4 at x = 0 cm 3.cos  = 0.4 at x = 20 cm 2013/11/30Belle II TOP Mini Review 4 #events with IRS3B CFD 540k 400k 235k 250k 950k 700k  efficiency cos  = 0cos  = 0.4 Beam  x

5. Previous Results: TDC Dist. w/ IRS Peak widths were consistent, and understandable with chromatic dispersion, MCP-PMT and readout resolutions etc. Discrepancy still remained a.Mismatch in relative heights of TDC peaks (in various ways) b.Tail associated with each TDC peak c.Background All channels analyzed by peak finding/fitting to extract timing resolutions. Monte Carlo has 100 ps electronics contribution as expected from laser results a a bb c data Monte Carlo a a b c c Typical TDC distributions w/ IRSTiming widths of all peaks in ring image Monte Carlo Data 2013/11/30Belle II TOP Mini Review 5

6. Previous Results: N hit w/ IRS Shown at the Belle II focused review in Sep. 2013. Note ; LEPS spectrometer data were not combined yet. – No cuts applied to hits included (e.g. no amplitude cut) – No cuts made on external counters to remove showering events data Monte Carlo data Monte Carlo data Monte Carlo cos(θ) = 0, x = 0cos(θ) = 0.44, x = 0cos(θ) = 0.36, x = 20 cm Long tail in data is likely due to showering and bremsstrahlung 2013/11/30Belle II TOP Mini Review 6

7. Previous Results: N hit w/ CFD Shown at the Belle II focused review in Sep. 2013. N tof = 1 to minimize showering events (but still remain). N hit counted inside 0 < t < 100ns. 2013/11/30Belle II TOP Mini Review 7

8. MC Simulation Geometry – A TOP module positioned with bar / mirror / prism dimensions and QBB box as in the prototype. – Alignment of the module Quartz optics – Bulk transmittance, surface reflectance – Mirror reflectivity (86%) – Others (polarization phase shift, chamfer, glue, …) MCP-PMT – QE (NaKSbCs, λ-dependence, angle dependence, …) + CE (55%) – Wavelength filter ( IHU340 ） – TTS: measured distribution ( ~35 ps for the main Gaussian) – Charge sharing + Cross talks – Reflection at surface – Others (alignment within the MCP-PMT module ) Readout – T-zero and electronics jitters – Hit detection efficiency Beam – Material effects (various materials along the beam) – Beam divergence 2013/11/30Belle II TOP Mini Review 8 Effects considered for new results.

9. Diagnostics in TDC dist. CFD data (cos  = 90 deg., x = 0 cm) compared to basf2 MC. 2013/11/30Belle II TOP Mini Review 9

10. Alignment Construct likelihood from product of observed intensity (ring image) with predicted intensity (PDF) Scan across track parameters to identify likelihood maximum 2013/11/30Belle II TOP Mini Review 10 Most likely parameters for alignment θ

11. Alignment Beam alignment with PDF: before/after Careful alignment improves matching between data and MC. 2013/11/30Belle II TOP Mini Review 11 Exp4 Exp2 Exp3 w/ IRS3B

12. Cont’d Beam alignment with PDF: before/after Careful alignment improves matching between data and MC. 2013/11/30Belle II TOP Mini Review 12 Exp4 w/ IRS3B

13. Material Distribution Materials (triggers and trackers) cause showers, and give – Additional hits by e ± and γ Hits preceding the 1 st peak and others hits with larger TDC width. – Beam scattering – Energy distribution of incident positrons. by beam e + by δ rays Nhit = 25.7 in 0<t<40ns Nhit = 6.0 in 0<t<40ns 2013/11/30Belle II TOP Mini Review 13 w/ CFD

14. Material Distribution Inclusion of these materials in MC improves match with data for – Tails in the N hit distribution 2013/11/30Belle II TOP Mini Review 14

15. Material Distribution Inclusion of these materials in MC improves match with data for – Tails in the N hit distribution – Hits preceding the 1 st peak in TDC distribution PMT1 2013/11/30Belle II TOP Mini Review 15 w/ CFD

16. Cross-talk / Charge sharing Cross-talk and charge sharing hits have slightly different timing and cause TDC timing tails. Rates of cross talks and charge sharing are estimated using laser data and also beam data. – CFD: Average rate is about 10% for charge sharing + 3%. for cross-talk – IRS: 4% cross-talk for a neighboring channel  11-12% in overall 2013/11/30Belle II TOP Mini Review 16 CFD data

17. Reflection at MCP-PMT surface Laser calibration data indicates that ~10% of photons are reflected on MCP-PMT surface, bounced back by the mirror, and make peaks at large TDC values. 2013/11/30Belle II TOP Mini Review 17

18. Surface Reflectivity Apply correction taking account of the incident-angle dep ( old MC assumed perfect reflection, no angle dep.). 2013/11/30Belle II TOP Mini Review 18

19. Cont’d Geant4 uses the unified surface model with many micro-facets (developed at TRUMF) The (gaussian) variation of the tilt angle is given by the parameter σ α, determined to be 0.000125, from the metrology report for the Zygo bar. The effect is the most evident for TDC peaks for long propagation. 2013/11/30Belle II TOP Mini Review 19 Inclusion of chamfers in MC also has the similar effect.

20. New Results Present new comparison plots for 1.Ring Images 2.TDC distribution 3.N hit distribution 4.Beta resolution 5.Pseudo likelihood and fake rate 2013/11/30Belle II TOP Mini Review 20

21. New Results: Ring Image Exp 2. cos θ = 0 2013/11/30Belle II TOP Mini Review 21 w/ IRS3B

22. Cont’d Exp 3. cos θ ~ 0.44, x ~ 0 cm 2013/11/30Belle II TOP Mini Review 22 w/ IRS3B

23. Cont’d Exp 4. cos θ ~ 0.36, x ~ 20cm 2013/11/30Belle II TOP Mini Review 23 w/ IRS3B

24. New Results: Ring Image Exp1, in log scale 2013/11/30Belle II TOP Mini Review 24 w/ CFD

25. New results: TDC w/ IRS 2013/11/30Belle II TOP Mini Review 25 Exp2: cosθ = , PMT#1, channel #9 Blue = MC Black = Data PMT # 1, Channel # 9 Data/MC peak positions agree fairly well Systematic excess of hits in real data is largest at early times

26. New results: TDC w/ IRS 2013/11/30Belle II TOP Mini Review 26 Exp2: cosθ = , PMT#24, channel #9 Blue = MC Black = Data PMT # 24, Channel # 9 Peak normalization agrees in some cases, disagrees in others. Sign that alignment needs tuning?

27. New results: N hit w/ IRS 2013/11/30Belle II TOP Mini Review 27 Exp2: cosθ =  Counts hit in -114 <TDC< -14 ns Require N tof = 1 to suppress shower events Measurement Period: -114 to -14ns Blue = MC: Mean = 23.4 Black = Data: Mean = 32.1

28. New results: N hit w/ IRS 2013/11/30Belle II TOP Mini Review 28 Exp 3 cos θ ~ 0.44, x ~ 0 cm Exp 4 cos θ ~ 0.44, x ~ 20 cm Blue = MC: Mean = 15.0 Black = Data: Mean = 19.6 Blue = MC: Mean = 13.9 Black = Data: Mean = 19.0

29. New Results: TDC w/ CFD With all inputs to MC, better agreement between data and MC is obtained also for TDC distributions. – Background, esp. hits before the 1 st peak, are reproduced by δ-ray /shower tracks produced materials upstream the TOP modeule. – Tail components are reprodcued by cross-talks and background. 2013/11/30Belle II TOP Mini Review 29 Data MC 66-deg. tilted track Time (ps) BG from  -ray Mirror ref. Data MC Time (ps) Normal incidence Cross-talk and BG Mirror ref.

30. New Results: N hit w/ CFD With all inputs to MC, better agreement between data and MC is obtained for N hit distributions 2013/11/30Belle II TOP Mini Review 30 Exp01: cos θ = 0 Exp01: cos θ ~ 0.4Exp01: cos θ ~ 0.4, x ~ 20cm Data MC Data MC Data MC

31. Beta Resolution Good agreement between data and MC. No significant dependence on N hit 2013/11/30Belle II TOP Mini Review 31 σ β for N hit = 30 Data MC σβσβ β N hit β w/ CFD

32. Pseudo Likelihood & Fake Rate 2013/11/30Belle II TOP Mini Review 32 Pseudo likelihood ratio analysis – lnL1 (β = 1) – lnL2 (β = 0.987 [3GeV/c Kaon]) Exp.1 Data MC Old New Data MC w/ CFD

33. Remaining Issues Better understanding of – Materials in front and rear the TOP (triggers, trackers) – Materials in LEPS spectrometer (drift chambers, …) – Run conditions (difference between IRS and CFD runs) – Beam divergence (easily affect  resolution) – Synchronization of LEPS and TOP data – Etc. Improve comparison – For IRS data – For CFD data (slight difference in fake rate …) 2013/11/30Belle II TOP Mini Review 33

34. Overall TDC Distribution w/ IRS 2013/11/30Belle II TOP Mini Review 34 Exp2: cosθ =  Excess before the 1 st peak Excess between TDC peaks Excess decreases for larger time “mirror” (photons reflected by the mirror) “direct”

35. temp Background Distribution 2013/11/30Belle II TOP Mini Review 35 MCMC w/ only δ-ray MC w/o δ-ray

36. Summary Extensive studies have been made for detailed MC tuning to match the beam test data. Obtained good agreement between data and MC. – By taking account of materials (triggers/trackers), cross- talk & charge sharing in PMT, quartz properties etc. Need further studies for full understandings – N hit difference in IRS data – Slight difference in fake rates for CFD data Level of agreement, esp. for CFD, is high to demonstrates the Belle II TOP optics. 2013/11/30Belle II TOP Mini Review 36

37. Backup Materials 2013/11/30Belle II TOP Mini Review 37

38. Ring image Normal incidence, CFD readout channel Time (ns) channel Time (ns) DataMC … ch.015 127 Mirror reflection Delta-ray BG

39. Ring image (exp.1, log) … ch.015 127

40. Ring image (exp.2)

41. Ring image (exp.2, log) 41

42. TDC distributions (exp.1) 42

43. TDC distributions (exp.2) 43

44. Overall TDC Distribution w/ IRS 2013/11/30Belle II TOP Mini Review 44 Exp 3 cos θ ~ 0.44, x ~ 0 cm Exp 4 cos θ ~ 0.44, x ~ 20 cm

45. New results: N hit w/ IRS 2013/11/30Belle II TOP Mini Review 45 Exp2: cosθ =  Counts hit in -114 <TDC< -64 ns Excess of 9.2 hits in data w.r.t. MC Measurement Period: -114 to -64ns Blue = MC: Mean = 20.1, RMS = 6.0 Black = Data: Mean = 29.3, RMS = 12.0

46. Correction for Excess Hits 2013/11/30Belle II TOP Mini Review 46 Data/MC TDC Distribution PMTs 1-16 Data/MC TDC Distribution PMTs 17-32 Hit Excess Measurement Period for PMTs 1 - 16 Hit Excess Measurement Period for PMTs 17 - 32 Background hits not associated with Cherenkov peaks contribute an additional ~7.4 hits/event to experiment 2 data assuming a flat distribution. Need to cut or simulate this background.

47. Shower Suppression w/ N tof = 1 N hit comparison w/ and w/o N tof = 1 cut. 2013/11/30Belle II TOP Mini Review 47