1 A first look at the KEK tracker data with G4MICE Malcolm Ellis 2 nd December 2005.
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Transcript of 1 A first look at the KEK tracker data with G4MICE Malcolm Ellis 2 nd December 2005.
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A A ffirst look at the KEK irst look at the KEK ttracker racker ddata with ata with G4MICEG4MICE
Malcolm Ellis 2nd December 2005
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ContentsContents
• Software• Data• Calibration• Decoding• Space Points• Alignment• Tracking• Light Yield• Next Steps
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SoftwareSoftware
• 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.
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DataData
• 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.
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CalibrationCalibration
• 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!
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Calibration procedureCalibration 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
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DecodingDecoding
• 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.
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Checking the DecodingChecking the Decoding
Station B
Station A
Station C
Station D
Pick the same view from3 or 4 Stations
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Checking the DecodingChecking 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.
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Decoding Plane X : A + B-> CDecoding Plane X : A + B-> C
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Decoding Plane X : A + B -> Decoding Plane X : A + B -> DD
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Decoding Plane V : A+ B -> Decoding Plane V : A+ B -> DD
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Decoding Plane W : B + C -> Decoding Plane W : B + C -> DD
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Space PointsSpace 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!
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Triplet ResidualTriplet Residual
X
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AlignmentAlignment
• 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)
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Alignment checksAlignment 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.
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Alignment: B + D -> AAlignment: B + D -> A
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Alignment: B + D -> CAlignment: B + D -> C
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TrackingTracking
• 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!
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Event DisplayEvent 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.
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Run 1257: First event with a Run 1257: First event with a tracktrack
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Run 1257: Second event with a Run 1257: Second event with a tracktrack
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Run 1257: Third event with a Run 1257: Third event with a tracktrack
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Run 1257: Fourth event with a Run 1257: Fourth event with a tracktrack
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Track chiTrack chi22 per D.O.F. per D.O.F.
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Residuals in Station BResiduals in Station B
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Residuals in Station AResiduals in Station A
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Residuals in Station CResiduals in Station C
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Residuals in Station DResiduals in Station D
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Cluster in Track: Station B View Cluster in Track: Station B View VV
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Cluster in Track: Station B View Cluster in Track: Station B View XX
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Cluster in Track: Station B View Cluster in Track: Station B View WW
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Cluster in Track: Station A View Cluster in Track: Station A View VV
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Cluster in Track: Station A View Cluster in Track: Station A View XX
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Cluster in Track: Station C View Cluster in Track: Station C View XX
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Cluster in Track: Station C View Cluster in Track: Station C View WW
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Cluster in Track: Station D View Cluster in Track: Station D View VV
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Cluster in Track: Station D View Cluster in Track: Station D View XX
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Cluster in Track: Station D View Cluster in Track: Station D View WW
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Light Yield SummaryLight Yield Summary
Station Plane V Plane X Plane W
B 6.8 PE2500 ppm
6.0 PE5000 ppm
6.6 PE3500 ppm
A 5.8 PE5000 ppm
6.5 PE5000 ppm
C 6.8 PEmixed
6.3 PE5000 ppm
D 4.1 PE2500 ppm
4.6 PE2500 ppm
4.4 PE5000 ppm
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Next StepsNext 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…