1. 1 A first look at the KEK tracker data with G4MICE Malcolm Ellis 2 nd December 2005

2. 2 Contents Software Data Calibration Decoding Space Points Alignment Tracking Light Yield Next Steps

3. 3 Software All results presented were produced using the tag tracker_20051201 of G4MICE. The application “Kek2005” was used to produce histograms. The application “EventDisplay” was used to produce the event display images. Calibration file used was that produced by me in November. Decoding file used was that produced by Hideyuki and Makoto. Reconstruction of hits requires a signal on a single channel of at least 2.0 PE.

4. 4 Data The data used for this analysis was one run (number 1257) which was taken with the beam at 3 GeV/c. This run was taken with no magnetic field and with the tracker aligned with the incoming beam. The run contains 20,000 triggers. I have made no cuts on the PID detectors, track defining scintillators, nor on the AFE related time signals.

5. 5 Calibration Two large runs (1166 and 1168) were taken with the LED pulser on cassettes 105 and 111 respectively. A G4MICE application (not in CVS, but far less complicated than the one that is) takes the raw ADC value and makes one histogram per channel. A kumac is then used to find the first two peaks (pedestal and first PE) and attempt to fit two gaussians plus a background to determine the gain. The same application, used on the physics data, was used to create histograms from which the pedestals could be obtained. Due to changes in the electronics between the calibration run and the physics run, the pedestals in the calibration run are not the same as those for the physics runs!

6. 6 Calibration procedure For each channel: –The kumac tries to find the first two peaks (ignoring a potential local maximum in between the first two real peaks). –The difference is compared to the typical value for the cassette and kept if it is reasonable (within ±25% of average). If not, the average for that cassette is used for this channel. –The kumac then uses the peaks as seeds for a fit to two gaussians and a P2 background. –If the fitted gain is within 4 ADC counts of the previously determined estimate, the fitted gain is used. –Otherwise, the previously determined estimate is used for this channel. –Kumacs and plots for all 2048 channels are on the web: http://home.fnal.gov/~mellis/mice/scifi_tracker/plots/plots.html

7. 7 Decoding There are two parallel sets of work to determine the decoding. G4MICE can now use the results from both techniques. Neither agree with each other, and I feel that at the moment, neither is 100% correct. For this analysis, I have used the decoding file produced by Hideyuki and Makoto.

8. 8 Checking the Decoding Station B Station A Station C Station D Pick the same view from 3 or 4 Stations

9. 9 Checking the Decoding Station B Station A Station C Station D Extrapolate from two stations to the other(s) Only 2D information (coordinate along plane, Z) For example: Take position in Stations B and A, extrapolate to Station C. Plot extrapolation in C vs. hit position in Station C.

10. 10 Decoding Plane X : A + B-> C

11. 11 Decoding Plane X : A + B -> D

12. 12 Decoding Plane V : A+ B -> D

13. 13 Decoding Plane W : B + C -> D

14. 14 Space Points In Stations B and D we have all 3 views and can make triplets. An internal residual can be defined which is the difference in X between the position of the hit on the X view, and the position of the crossing of the hits in the V and W view. Distribution shows a peak which should be at 0 for good triplets. An offset in X is required in order to position this peak at 0. This offset is actually the offset in counting the fibres. The first electronic channel on a plane is not necessarily reading out the fibre at the same distance from the centre of the station!

15. 15 Triplet Residual XX

16. 16 Alignment With Stations B and D internally aligned, they can now define a coordinate system. Making a track between good triplets in Stations B and D, extrapolations to space points in Stations A and C allow the two stations to be centred on this coordinate system. The station spacing in Z is left fixed at the values determined by the CMM. Stations are assumed to have the following properties: –Exactly parallel –Exactly perpendicular to the Z axis –Exactly aligned in angle about the Z axis (i.e. no twisting)

17. 17 Alignment checks For each of stations A and C, I extrapolate the track built from triplets in Stations B and D and plot the residual versus the position of the extrapolation (X and Y). Ideally, this plot would have a flat band, along the X axis of the plot (i.e. zero residual independently of where in the tracker the track was). The data show discrete steps away from 0 at certain locations in the two stations. My interpretation of this is that there is still something wrong with the decoding. It may also be the result of twisting or other rotational effects in the tracker support frame. This needs to be resolved before any serious analysis of the data requiring track fits can be done.

18. 18 Alignment: B + D -> A

19. 19 Alignment: B + D -> C

20. 20 Tracking With the “least bad” decoding and alignment, and with the road widths for track finding opened up, the straight line track fit is used. Some of the standard monitoring histograms, prepared for the KEK test, are shown to illustrate the quality of the tracks and the light yield per station. Remember that no cut on PID or on AFE timing has been made!

21. 21 Event Display The following slides show the first four events in run 1257 that have a reconstructed track. Hits are displayed in Yellow if they are part of the track and black if they are not. The track itself is shown as a green line.

22. 22 Run 1257: First event with a track

23. 23 Run 1257: Second event with a track

24. 24 Run 1257: Third event with a track

25. 25 Run 1257: Fourth event with a track

26. 26 Track chi 2 per D.O.F.

27. 27 Residuals in Station B

28. 28 Residuals in Station A

29. 29 Residuals in Station C

30. 30 Residuals in Station D

31. 31 Cluster in Track: Station B View V

32. 32 Cluster in Track: Station B View X

33. 33 Cluster in Track: Station B View W

34. 34 Cluster in Track: Station A View V

35. 35 Cluster in Track: Station A View X

36. 36 Cluster in Track: Station C View X

37. 37 Cluster in Track: Station C View W

38. 38 Cluster in Track: Station D View V

39. 39 Cluster in Track: Station D View X

40. 40 Cluster in Track: Station D View W

41. 41 Light Yield Summary StationPlane VPlane XPlane W B6.8 PE 2500 ppm 6.0 PE 5000 ppm 6.6 PE 3500 ppm A5.8 PE 5000 ppm 6.5 PE 5000 ppm C6.8 PE mixed 6.3 PE 5000 ppm D4.1 PE 2500 ppm 4.6 PE 2500 ppm 4.4 PE 5000 ppm

42. 42 Next Steps Still need to sort out decoding and geometry. Once current G4MICE work (Simulation and Digitisation) is finished, will start implementing more sophisticated geometry for SciFi tracker so we can cope with alignments and rotations at any level. Once TOF code in G4MICE is ready (soon) more sophisticated analyses using PID will be possible. Can already consider looking at D1/D2 and AFE timing signals…