sPHENIX MAPS tracker discussion

[Yasser Corrales Morales <ycmorales AT rcf.rhic.bnl.gov>]

Hi Tony,

One question,

when you get the local position in the sensor from  world  coordinates did  you use "get_sensor_indices_from_world_coords"?

I ask you because it is a method I haven't tested before.

could you point me to the code to get ACTs surface world/local coordinates for test?

thank you,

Y.

    On 5/30/20 22:29, Anthony Frawley wrote:
    
      
      
      
        Dear MVTX experts,
      
        
      
      
        While working on the Acts implementation, I turned up a
        discrepancy between the MVTX geometry extracted by Acts from our
        G4 model, and the description of that geometry in the geometry
        class "mvtx/CylinderGeom_Mvtx".
        
      
      
        
      
      
        The Acts code analyzes the TGeo objects in the G4 model and
        extracts a "Surface" corresponding to each active detector
        volume. The Acts Surface class has a transformation that returns
        the local position on the surface corresponding to a given world
        position. Our geometry classes have methods that do the same
        thing. They get the same answer for the INTT and TPC, but do not
        get the same answer for the MVTX.
        
      
      
        
      
      
        For the MVTX sensors, the local position is (x,z), where x is
        the (radius*phi) direction. The local z position agrees
        perfectly, but the local x position is always different by
        0.03872 mm. Also, the Acts surface center in world coordinates
        is slightly different from the sensor center given by
        CylinderGeom_Mvtx. 
      
      
        
      
      
        I have looked carefully at CylinderGeom_Mvtx and there is no
        obvious logical error. Doing local-to-world / world-to-local /
        local-to-world transformations yields the exact starting value.
        The positioning of the staves in the geometry class seems to be
        the same as in the MvtxDetector class, which constructs the
        detector model. The discrepancy seems to be in the location of
        the sensor in the stave. Since the stave is not built in our
        software, we import it, I can not easily check that the geometry
        class has it right.
      
      
        
      
      
        My specific request to the experts is to check that the
        parameters in CylinderGeom_Mvtx that position the sensor in the
        chip, the chip in the module, and the module in the stave are
        all correct.
      
        
      
      
        Thanks
      
        Tony
      
        
      
      
        
      
      
        
      
      
        
      
      
      
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-- 
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Yasser Corrales Morales

Postdoctoral Research Associate
PO Box 1663
MS H846
LANL
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