SHMS Drift Chambers Calibration

This directory contains the code for calibrating the pair of SHMS drift chambers.

Directory structure

• hallc_replay/CALIBRATION/shms_dc_calib/run_Cal.C : steering C++ code that executes all codes in the 'scripts' directory
• hallc_replay/CALIBRATION/shms_dc_calib/scripts : all scripts necessary to do calibration lie in this directory
• hallc_replay/CALIBRATION/shms_dc_calib/root_files : all root files produced by the calibration are in this directory
• hallc_replay/CALIBRATION/shms_dc_calib/data_files : all data files produced by the calibration are in this directory

Running code

• First set the parameter 'p_using_tzero_per_wire = 0' in the parameter file located at: hallc_replay/PARAM/SHMS/DC/CUTS/pdc_cuts.param

• Replay the data to produce the uncalibrated root file to be used as input in the calibration

  • From the hallc_replay execute: ./hcana SCRIPTS/SHMS/STACK/replay_shms.C

• From the directory where this README file is: execute: root -l run_Cal.C

• From the calibration results, two parameter files will be produced in:

  • hallc_replay/PARAM/SHMS/DC/CALIB/pdc_tzero_per_wire_run#.param
  • hallc_replay/PARAM/SHMS/DC/CALIB/pdc_calib_run#.param

• Rename the new parameter files as follows:

  • copy: pdc_tzero_per_wire_run#.param to pdc_tzero_per_wire.param
  • copy: pdc_calib_run#.param to pdc_calib.param

• Before replaying the data again, set the parameter 'p_using_tzero_per_wire = 1' to allow the source code (hcana) to read the parameter values during the replay.

• Replay the data with the updated parameters to produce the new calibrated root files with the corrected drift times and drift distances.

• Compare the calibrated and uncalibrated root files to verify the calibration was done properly.

Brief decription of code

• Overview: The code determines the tzero offsets on a wire-by-wire basis. These offsets are corrections by which each wire drift time spectrum must be shifted to align it with a drift time of "0 ns". This time corresponds to when the electrons from the ionized gas inside the chamber are in contact with the sense wire, hence a drift time of "0 ns".

• Brief Description of the scripts in the '/scripts' directory *** to run the scripts independenlty, open the input_RUN.txt files and write the filen_ame, run_number and number of events in this order: root_file.root run_number events

  ** get_pdc_time_histo.C : -- outputs root_file: 'shms_dc_time_%d.root', (%d=run_number) -- contains re-binned per-plane drift time histograms

  ** wire_drift_times.C (and wire_drift_times.h) - See instructions in wire_drift_times.C on how to execute independently -- outputs root_file: 'shms_DC_plane_%d_wire_histos.root' -- contains a 2-D histo of "drift time vs. Wire Number" and drift time spectra for all wires in the plane

  ** get_wire_tzero.C -- outputs root_file: 'shms_DC_plane_%d_fitted_histos.root' -- contains line-fitted wire drift time histos. The extrapolation of the fit to the x-axis is defined as "tzero" Also contains two "tzero vs. wirenumber" plots: one for all wires, and the other is after setting tzero=0 for wires that did not have enough statistics for a good quality fit, a weighted average was calculated for the latter.

    -- outputs data_file: 'shms_dc_planetzero_run%d.dat'         -> contains list of "tzero" values for all wires  (plane e.g. 2u1, 1x2, ...) 	
       	   	      'shms_dc_planetzero_run%d_updated.dat' -> contains list of "tzero" values for all wires that
    		      					     	had a good fit. The remaining tzeros are set to 0.
    		      'tzero_weighted_avg_run%d.dat          -> contains weighted tzero values per plane 

  ** get_tzero_per_wire_param.C -- outputs data_file: 'tzero_values_per_wire.dat' -- contains list of tzero values for all wires in all planes

    -- outputs param_file: /hallc_replay/PARAM/SHMS/DC/CALIB/pdc_tzero_per_wire_run#.param
            -- contains tzero values for all wires in all planes, but the file is formatted so that the values may be read by the source code (hcana)

  ** get_pdc_time_histo_tzero_corrected.C -- outputs root_file: 'shms_tzero_corr_histo.root' -- contains list of "t0-corrected" wire drift times, and their respective plane drift times.

  ** get_LookUp_Values.C -- outputs param_file: /hallc_replay/PARAM/SHMS/DC/CALIB/pdc_calib_run#.param -- contains scaling factors calculated from the corrected plane drift times on a bin-by-in basis. These values get read by the source code which will be used to scale the drift distance histograms.