sPHENIX discussion of physics

[Anthony Frawley <afrawley AT fsu.edu>]

Hi All,

K-short with residual misalignments (Tony Frawley)

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Study of tracking reconstruction performance for K-short decays with four levels of random detector misalignments.

  σ = 40%, 80%, 160% and 320% of the intrinsic cluster resolution in the azimuthal plane.

Question: Were these tests run with the commissioning track seeding settings? 

No, the seeding was done with the normal seeding windows. 

Should try commissioning seeding settings for the larger misalignments.

Question: Would like to have students start now to look at the effect of misalignments on Ks, D0, J/psi, Upsilon performance. 

How to use the misalignment files?

1) The files have been placed at:

/sphenix/tg/tg01/hf/frawley/test_misalignment_files

  localAlignmentParams_mvtx2_intt10_tpc60.txt

  localAlignmentParams_mvtx4_intt20_tpc120.txt

  localAlignmentParams_mvtx8_intt40_tpc240.txt

  localAlignmentParams_mvtx16_intt80_tpc480.txt

where the numbers are the sigma in μm of the random displacements (dx,dy,dz) that mimic the effect of residual misalignments after the alignment process.

2) Copy the relevant text file to the local directory from which you run the process, renaming it "localAlignmentParamsFile.txt".

The reconstruction code will look for that file locally, and if it exists it will modify the ideal local/global transformations for the surfaces to include those perturbations. Otherwise, the ideal (simulation) geometry will be used.

3) Run the reconstruction as usual.

Question: What is the effect of pileup on the performance?

There is no pileup in the events used here. There was an issue accessing the MDC2 files at the time of the tests, so they were done by running single Pythia8 events with the default settings.

Future tests should be done with g4hits files from MB Pythia events with pileup.

But, based on past experience, I do not expect much effect. In an extended readout event, the tracks are all assigned to their collision vertex, so there is no increase in combinatorics. The only effect would be from higher cluster occupancy.

 Tony