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Minuit Alignment Code - Automated Track Alignment for Magnetic Field Effects

This code outlines the idea behind Minuit alignment code and how it can be used to align tracks in the presence of correlated parameters. It provides a step-by-step structure for the code and includes information on the output tracks, preparation for the fit, and the fitting process using Minuit. The code's performance is demonstrated with a test on a magnet run. Further improvements and future plans are also mentioned.

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Minuit Alignment Code - Automated Track Alignment for Magnetic Field Effects

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  1. Minuit Alignment Code Jianchun Wang 02/14/00 Outline • The idea behind the code • Code structure and its usage • Test on a magnet run • Plan Jianchun (JC) Wang

  2. Motivation Existing hand alignment • too slow • difficult to deal with correlated parameters Minuit alignment • work on saved tracks (avoid unnecessary calculation) • correlated parameters can be fitted together • can be automated Jianchun (JC) Wang

  3. Code structure • First stage: output track for later fitting user(‘event’)  mn_write_track • Subsequent stages: read in track and fit user(‘endrun’)  mn_prepare_fit  mn_read_track  mn_fit_geo  mn_geo_copy  mn_geo_chi2  mn_geo_copy  mn_derived_geom  mn_fit_tracks Jianchun (JC) Wang

  4. Output Tracks • Only one track in the event • At least two good Y hits • Number of Planes with hits is kept • Local position and sigma are kept • Chi2 of Kalman fit is also kept for comparison ( y slope floating, all y information in the fit) • Output file name “track_out.dat” Jianchun (JC) Wang

  5. Preparation for the fit • Links of geometry planes to Kalman planes created only once to save time • Tracks input from file “track_in.dat” • All track properties stored with a format suitable for Kalman fitting • Planes can be dropped at this stage Jianchun (JC) Wang

  6. Minuit fitting • Parameters for fit • Provided by “mn_skip.dat”, changeable during run • Manipulate parameters interactively in Minuit • Parameter transfer • New geometry parameters in monitor format (mn_geometry.dat) • Geometry parameter  Minuit parameter • Function of the fit • Chi2 of Kalman fit averaged over n.o.f and ntrack Jianchun (JC) Wang

  7. 2 of Kalman fitting • Magnet run 7236 (15o) • 20K events • 10K tracks selected • Hand alignment before create track file • MINUIT fit use only simple fit with part of parameters • 2 is not normalized to n.o.f Jianchun (JC) Wang

  8. Resolution of FPIX1 • FPIX1 pspray at 15o • The resolution is not changed (~11m) • For rough comparison only (magnetic field effects) Jianchun (JC) Wang

  9. Residual of FPIX0 • FPIX0 pstop rotated and placed in magnetic field (~ 17.5 A) • Only two pixel clusters shown, and the improvement is only due to a bug fixed in eta correction • For comparison only Jianchun (JC) Wang

  10. What is next ? • MC test to have objective evaluation (Rob has running MC) • Input & output control • Create procedure of the fitting • Make it more automatic • Align all runs ( how to share the work, and CPU availability) Jianchun (JC) Wang

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