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Outer to Inner sector alignment using Y2011 Cosmic data

Updated on Wed, 2011-08-03 09:23. Originally created by fisyak on 2011-08-02 12:21.

 

Outer to Inner sector alignment using Y2011 Cosmic data

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    I try to digest results obtained for Outer to Inner (sub) sector alignment using Cosmic data from run XI for both Reverse Full Field and Full Field. 

The method is following:

  • For tracks reconstructed by Sti
    • with more than 10 fit points in a super sector and momentum > 1 GeV/c
    • and confirmed in ToF
  • Hits
    • in TPC local  sector coordinate system (Sector12),
    • with  distortion corrections "Corr4,-OBmap2D,-OTwist,OBmap" : 
      • i.e. with 3D corrections (instead of 2D)
      • with Mag. Field calculated in TPC local coordinate system (accounting “TWIST”), 
    • and corrected on time of flight  are
    • fitted by helices separately for inner and outer sub sectors (with a least 5 hits per helix) in the same super sector, with hit errors used in the Sti reconstruction.
  • For the helices
    • which have chi2/NDF < 5 and
    • difference in curvatures < 6e-3
    • their parameters were propagated to plane Y = 123 cm (~middle of Super sector)  and compared.
  • From the comparison 6 parameters (ΔX, ΔY, ΔZ, Δα, Δβ, Δγ):
    • shifts in X,Y,Z and rotations around X,Y,Z axises, respectively, for Outer subsector with respect to Inner one.
    • are fitted

Results of alignment (the above 6 parameters for each sector) for RFF (red) and FF (black)  with old alignment parameters   (red line - Y2001, green line - Y2010) are presented below.

I consider these results as the final for Y2011.

My conclusions from the above plots:

  1. All other paramters (ΔY, ΔZ, Δα, Δβ) show practically no dependence on magnetic field. (We should take out of consideration sector 20 which is bad and sector 4 which does not have inner sub sector for FF). I would consider that these parameters reflect real mechanical TPC deformations.
  2. ΔX and  Δγ (bending plane) plots show strong dependence versus the direction of magnetic field. The difference is kind of swap sign for West and East part of Tpc.
  3. The plot dX versus drift distance (see below) separately for West and East part of TPC and for both configurations of magnetic field show very small drift distance dependence.
  4. From this plot I made conclusion that the above alignment dependence on magnetic field is due to configuration of electric field near the anode wires.
     
  5. .
     

 

 

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