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Documentation of libsbsdig » History » Version 19

Eric Fuchey, 07/09/2020 12:46 PM

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h1. Documentation of libsbsdig
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h2. Overview
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This page is maintained by the UConn group (Eric Fuchey + Andrew Puckett) and as of February 14, 2020 is specific to the '''''master''''' branch of libsbsdig on github.
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h2. Purpose
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This page documents the libsbsdig code, which purpose is to transform the output data from [https://hallaweb.jlab.org/wiki/index.php/Documentation_of_g4sbs G4SBS] to digital values such as ADCs or TDCs.
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These produce files which can be analyzed with [https://hallaweb.jlab.org/wiki/index.php/Documentation_of_SBS-offline SBS-offline].
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h2. Getting the code and building the program
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h3. Prerequisites
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*Working [https://root.cern.ch/drupal/ ROOT] installation. '''libsbsdig is compatible with ROOT version 5 and ROOT version 6'''. '''''ROOT 6 is strongly recommended'''''
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*Working [https://redmine.jlab.org/projects/podd/wiki analyzer] installation. '''libsbsdig is compatible with analyzer versions 1.6 and beyond'''.
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*Working [https://hallaweb.jlab.org/wiki/index.php/Documentation_of_SBS-offline SBS-offline] installation.
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h3. Downloading the repository
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The code is hosted on a github repository owned by JLab. To clone via ssh (preferred method on JLab batch farm), do: 
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bq. git clone git@github.com:JeffersonLab/libsbsdig.git
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For this method to work, the ssh public key on the machine where you want to get the code must be added to your github account (see [https://help.github.com/articles/generating-ssh-keys/ Guide] to generating ssh keys and adding to your github.com account.)
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Cloning the repository defaults to the "master" branch.
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h3. Building and installing the library
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Create a "build" directory that is parallel to the "libsbsdig" source directory (this is not strictly required, but the build directory must be separate from the "SBS-offline" directory in any case). 
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You also need to have setup an installation path e.g. /path/to/libsbsdig-install
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*NB*: similarly to the build directory, the /path/to/libsbsdig-install directory shall '''not''' be the same as the source directory!
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_The following instructions assume that "build" is parallel to "libsbsdig":_
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If successful, the libsbsdig library and several other files and folders will be created in the "build" and the "install" directory.
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To build and install, the procedure needs to be completed. From scratch:
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bq. mkdir build
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cd build
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cmake -DCMAKE_INSTALL_PREFIX=/path/to/libsbsdig-install ../libsbsdig
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make install
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Then, the following line should be added in the OS login configuration file to take advantage of this functionality:
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* source /path/to/libsbsdig-install/bin/sbsdigenv.sh (or source /path/to/g4sbs_install/bin/sbsdigenv.csh on the batch farm)
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h2. digitization library use
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h3. how to use the digitization library
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A working example script of using the digitization library is available in the libsbsdig repository at
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example/digi_gmn.C 
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The input arguments for this scripts are explained in the script comments. 
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It has to be executed with the Hall A analyzer:
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> analyzer
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> > .L digi_gmn.C
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> > digi_gmn("simdig_outfile.root", 1000, "gmn13.5_elastic_prod.txt")
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h3. Root output documentation
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For each detector, several structures are stored under the form of an ensemble of vectors of integers and doubles.
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There are three types of structures:
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- the "trackmchits" storing the information of the Monte Carlo track intercepting the detector; 
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- the "simhits" storing the true energy deposits and corresponding number of photoelectrons for each g4sbs hit processed by libsbsdig;
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- the "hits", storing the adc and tdc information;
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h4. "trackmchit" structure
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nhits (int): number of entries for this structure and this detector
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source (std::vector<short>): type of file where the MC track comes from (0 if signal, >0 if background)
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trid (std::vector<short>): track ID in G4SBS (mostly useful to distinguish primary tracks)
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pid  (std::vector<int>): track PDG PID
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xhit (std::vector<double>) estimated point of intercept of the track at the detector surface, in the dispersive direction (transport coordinates)
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yhit (std::vector<double>) estimated point of intercept of the track at the detector surface, in the non-dispersive direction (transport coordinate)
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thit (std::vector<double>) estimated time of intercept of the track at the detector surface
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e (std::vector<double>) track total energy
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weight (std::vector<double>) weight of the event from which the track is issued (not implemented yet)
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h4. "simhit" structure
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nhits (int)
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src (std::vector<short>): type of file where the sim hit comes from (0 if signal, >0 if background)
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trid (std::vector<short>): ID of track responsible of hit in G4SBS (n. i. y.)
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pid (std::vector<int>): PDG PID of track responsible of hit in G4SBS (n. i. y.)
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chan (std::vector<short>): channel number in which the hit is recorded
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edep (std::vector<double>): energy deposit recorded in g4sbs (in GeV)
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npe (std::vector<int>): recorded or estimated number of photoelectrons detected
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time (std::vector<double>): time of hit as recorded by g4sbs or estimated by libsbsdig (if photons are estimated)
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t_lead(std::vector<double>): estimated time when the pulse rises over threshold (for detectors with TDCs) 
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t_trail(std::vector<double>): estimated time when the pulse falls under threshold (for detectors with TDCs) 
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Note: 
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for calorimeters without TDCs, t_lead and t_trail are not applicable and will not be stored;
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for cherenkov detectors, edep is not applicable and will not be stored;
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h4. "hit" structure
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nhits (int)
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chan (std::vector<short>)
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dataword (std::vector<unsigned int>)
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adc (std::vector<int>)
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tdc_l (std::vector<int>)
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tdc_t (std::vector<int>)
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   std::vector<unsigned int> *sbs_hcal_hit_nsamps;
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   std::vector<vector<int> > *sbs_hcal_hit_samps_adc;
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   std::vector<vector<unsigned int> > *sbs_hcal_hit_samps_datawords;