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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…