BRAHMS Global Tracking Enhancements
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Transcript of BRAHMS Global Tracking Enhancements
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BRAHMS Global Tracking Enhancements
K. Hagel
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Review of Original Procedure
• Start with Track position and direction at T1.
• Perform Minuit fit varying p, ydir using starting values of pave=(pd2+pd3+pd4)/3, ydir of track.
2 calculated on (x,y) positions of local tracks in other tracking stations.
• Swim backwards through D1 to vertex to obtain Zvtx, θ, .
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Enhancements to the code
• Vary t1X and t1Y as fit parameters
• Vary x direction as fit parameter
• Calculate 2 “correctly” using “known” σs of detectors (position and angle)– 350 m TPCx– 500 m TPCy– 200 m DCx– .5mr in θ bend plane
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X difference
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Y difference
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Theta difference
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Attempt to resolve differences in positions
• Shift detectors by difference of “where they want to be at”– t1y by -0.2cm– t2x by 0.1cm– t3y by 0.128cm
• Affects the chisq calculation
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X difference (modified)
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Y difference (modified)
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Theta difference (modified)