Start Counter Calibration Procedures

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Introduction

Currently, the plugins 1, 2, and 3 are in the sim-recon/src/plugins/Calibration. A summary of how to run each code and the expected outcomes of the macros will be shown in details.

  • 1) Start Counter Time Walk Corrections Plugin (st_tw_corr_auto)
  • 2) Start Counter Propagation Time Corrections Plugin (ST_Propagation_Time)
  • 3) Start Counter Time Resolution Plugin (ST_Tresolution)

ST Time Walk Plugin "st_tw_corr_auto"

This plugin must run in two passes. In the first pass the parameter USE_TIMEWALK_CORRECTION = 0.Therefore this plugin will generate a ROOT file from an EVIO data file that contains histograms of the time difference (self timing) versus pedestal-subtracted pulse peak amplitude for all 30 start counter sectors. A separate ROOT macro (st_tw_fits.C) will analyze and fit these histograms and provide a table for the CCDB. After uploading the constants into the CCDB, the plugin must run the second pass where USE_TIMEWALK_CORRECTION = 1. The Walk corrected times will be calculated during this pass. The ST self timing resolution is calculated using the macro st_tw_resols.C. In this macro verification plots for each sector is also created.

Plugin Files:

   JEventProcessor_st_tw_corr_auto.cc
   JEventProcessor_st_tw_corr_auto.h

Macros Files:

   st_tw_fits.C
   st_tw_resols.C

To run the plugin, use the following command:

hd_root -PPLUGINS=st_tw_corr_auto /path/to/datafile

To run the first pass macro , use the command :

.x st_tw_fits.C("hd_root.root")

The file st_timewalks.txt will be created with the needed constants for the walk corrections. To upload these constants into the CCDB use the command:

Add timewalk_parms_v2 st_timewalks.txt

After running the plugin for the second time, run the macro st_tw_resols.C using the command

.x st_tw_resols.C("hd_root.root")

Examples of the excpected plots can be found here ST_tw_corr

ST_Propagation_Time

This plugin must run after we have the walk corrected times from the ST and TOF. The first pass of this plugin will generate a ROOT file from an EVIO data file that contains histograms of the ST propagation time versus Z coordinate of the ST hit location for all 30 start counter sectors. A separate ROOT macro (st_prop_time_v1.C) will analyze and fit these histograms and provide a table for the CCDB through an output text file named (st_prop_time_constants.txt). In order to add these constants to the CCDB use the Command :

Add  propagation_time_corr st_prop_time_constants.txt

To check that these constants work fine run the plugin in the second pass using the command:

hd_root -PPLUGINS=st_tw_corr_auto /path/to/datafile 

Then run the macro st_prop_time_corr_v1.C using the command:

.x st_prop_time_corr_v1.C("hd_root.root")

When the corrected times are calculated use the ST_Tresolution plugin to calculate the ST time resolution.

ST_Tresolution

This plugin must run after the ST propagation time constants are uploaded in the CCDB. This plugin will generate a ROOT file from an EVIO data file that contains histograms of the ST corrected time for each paddle versus Z coordinate of the ST hit location. To run the plugin use the hd_root command mentioned in section 1 of this page. To run the macro use the command :

.x st_time_resolution.C("hd_root.root")

The output of this macro will be 30 canvas of the two dimensional histograms mentioned above in addition to Y projection of these histograms. The time resolution will be ploted in another canvas. Examples of these histograms can be found in the following link ST Propagation Time Correction and Time resolution