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Documentation of libsbsdig » History » Version 105

Eric Fuchey, 07/02/2021 11:23 AM

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h1. Documentation of libsbsdig
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{{toc}}
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This page concerns the new version of libsbsdig which is currently being developped. The documentation for the old version of libsbsdig has been saved at:
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https://redmine.jlab.org/projects/sbs-software/wiki/Old_Doc_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 *sbsdig_lw* 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 process the Monte Carlo simulations of the SBS experiments produced by G4SBS [https://hallaweb.jlab.org/wiki/index.php/Documentation_of_g4sbs] to produce ADCs or TDCs.
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It is a standalone program which can run with a limited number of outputs (see section on usage).
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These produce files which can be analyzed with SBS-offline [https://hallaweb.jlab.org/wiki/index.php/Documentation_of_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 ROOT [https://root.cern.ch/drupal/] installation. ROOT 6 is strongly recommended.
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* Working G4SBS [https://hallaweb.jlab.org/wiki/index.php/Documentation_of_g4sbs] installation.
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h3. Downloading the repository
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h4. for simple users
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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. _As of August, 18th, 2020, the master branch still contains the old version of the code_.
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*Beware that the current version of libsbsdig is not on the "master" branch, but on the "sbsdig_lw".*
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* Have an individual github account.
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* On github.com: Fork the JeffersonLab libsbsdig to your account. Setup to “watch” Jlab libsbsdig
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* git clone git@github.com:GithubUserName/libsbsdig.git (This is ssh access). 
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** This will be the “origin” remote repo;
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** Create your own branch: git checkout –b NewBranchName
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* git remote –add upstream git@github.com:JeffersonLab/libsbsdig.git
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** This will be the “upstream” remote repo
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* You can pull ( or fetch/merge) changes from the upstream (Jefferson Lab) repo.
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* You can push commits in your branch to the origin (Personal Github) repo and then make pull requests.
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To obtain the new version of the code currently being developped on the "sbsdig_lw" branch, do:
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bq. git checkout sbsdig_lw
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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 "libsbsdig" 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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For instance, you can create it parallel to your libsbsdig directory (with the mkdir command), even though it is not strictly required
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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/libsbsdig-install/bin/sbsdigenv.csh on the batch farm)
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h2. How to use the digitization library
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When sbsdig is installed in your machine, you can run the program using up to 4 arguments:
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bq. sbsdig db_gmn_conf.dat gmn13.5_elastic_ex.txt 100000
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These arguments have to come in this sequence, and while not all arguments are mandatory to provide, one cannot skip an argument unless they want to skip all following arguments.
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*The first argument is a database containing the list of detectors to digitize, and the parameters for the digitization. An example of such parameters is attached (db_gmn_conf.dat)
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*The second argument is a list of "signal" files to digitize. It is mandatory to provide. An example is provided in the files attached.
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This file contains a list of input files for the program to run on. Hence, it has to contain g4sbs files that you have permission to modify. 
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This file may also optionally contain the input for background superimposition. Input has to be of the form e.g. 
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 * gmn13.5_beambkgdhistos.root 80.0 1.0 0
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with: 1st parameter name of the file where the histograms are stored; 2nd parameter: time window (in ns) on which the background has been integrated; 3rd parameter: fraction of background wrt nominal luminosity we want to add; 4th is a flag to switch on or off the digitization of the PMT detectors background.
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*The third argument is the number of process. It has a default value of "-1" (=2^64-1) so it can be left unprovided.
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h2. Input files documentation
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h3. Configuration file
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This part describes the expected parameters for the configuration file (first argument for sbsdig). 
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These parameters are presented as follows: name (expected type): nature of the 
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* Rseed (int): seed for random number generator
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* TriggerJitter (float): global trigger jitter for all detectors in ns
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* detectors_list (strings, may take several arguments): list of detectors to digitize
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Currently implemented:
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hcal (hadron calorimeter, "pmt" type detector)
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bbps (Big Bite calorimeter preshower, "pmt" type detector)
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bbsh (Big Bite calorimeter shower, "pmt" type detector)
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grinch (BigBite GRINCH cherenkov, "pmt" type detector)
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bbhodo (BigBite timing hodoscope, "pmt" type detector)
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bbgem (BigBite GEM tracker, "gem" type detector)
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ecal (GEp electromagnetic calorimeter, "pmt" type detector)
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cdet (coordinate detector for GEp electron arm, "pmt" type detector)
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ft (GEp front tracker, "gem" type detector)
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fpp1 (GEp focal plane polarimeter 1, "gem" type detector)
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fpp2 (GEp focal plane polarimeter 2, "gem" type detector)
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GEnRP detectors being added...
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h4. Parameters for "pmt" type detector (name "det")
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* NChan_det (int) number of PMTs
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* gatewidth_det (float) size of the data acquisition window in ns 
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* gain_det (float) PMT gain
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* ped_det (float) channel pedestal mean
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* pedsigma_det (channel)  channel pedestal sigma
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* trigoffset_det (float) trigger offset to have the signal centered properly around zero
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* ADCconv_det (float) fC/ADC channels conversion factor
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* ADCbits_det (int) number of bits to store the ADC value
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* TDCconv_det (float) ns/TDC channels conversion factor
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* TDCbits_det (int) number of bits to store the TDC value
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* sigmapulse_det (float) full width half max of PMT pulse
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h4. Parameters for "gem" type detector (of name "detgem")
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* NPlanes_detgem (int): number of GEM modules x number of readout planes (usually 2) included in the tracker;
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* gatewidth_detgem (float): size data acquisition window for the in ns;
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* nlayers_detgem (int): number of GEM layers (ensemble of GEM modules at a same z)
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* detgem_layer_z (array of floats): z value of each layer (should match number of layers); 
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* layer_detgem (int): layer to which the plane/module/readout belongs; _array needs to be same size as NPlanes_detgem_
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* nstrips_detgem (array of ints): number of strips for each plane/module/readout; _array needs to be same size as NPlanes_detgem_
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* offset_detgem (array of floats): geometrical offset in transport coordinate for each plane/module in meters (alternatively x, y); _array needs to be same size as NPlanes_detgem_
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* RO_angle_detgem (array of floats): angle of readout in degrees, with respect to transport coordinate x; _array needs to be same size as NPlanes_detgem_
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* triggeroffset_detgem (array of floats): trigger offsets for all planes in ns _array needs to equal to NPlanes_detgem/2_
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* ZsupThr_detgem (float): zero suppression threshold for GEMs in ADC channels;
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* commonmode_array_detgem (float or array of floats) "common mode" (APV pedestal) value/array for BBGEMs in ADC channels; one can provide only one value which will be used for all strips or an array of values for a more realistic simulation
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h2. Root output documentation
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The new digitization library will expand the TTree object from the input file to add ADC and TDC values.
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The input tree structure from G4SBS has already been described in detail in the G4SBS documentation [https://hallaweb.jlab.org/wiki/index.php/Documentation_of_g4sbs#ROOT_Tree_Structure].
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The basic idea is that for each detector in the input tree, a set of branches will be added.
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There are several types of detectors in G4SBS (GEM, CAL, RICH), but there is not always a defined extension for a G4SBS detector type.
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(NB: I'm voluntarilly omitting ECAL, 
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For the purpose of the digitization, it is more convenient to define the following types of detectors:
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* GEM: GEM trackers. Corresponds unambiguously to GEM detector type in G4SBS. Read out by MPD (sampling ADC) modules.
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* Cher: Cherenkov detectors (example: GRINCH). Corresponds unambiguously to RICH detector type in G4SBS. Read out by TDC modules (with optional ADCs).
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* Scint: Scintillator timing detectors (example: Timing Hodoscope). Corresponds to CAL detector type in G4SBS. Read out by TDC modules (with optional ADCs).
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* Cal: Calorimeter (example: BBPS, BBSH). Corresponds to CAL detector type in G4SBS. Read out by ADC modules.
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* HCal: Hadron Calorimeter. Corresponds to CAL detector type in G4SBS. Read out by FADC (sampling ADC) modules with TDCs.
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h4. Data structure extension for "Cal" detector types:
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* nchan (int): number of channels (firing?)
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* chan (std::vector<int>) channel number
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* adc (std::vector<int>) unencoded pedestal subtracted ADC value
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h4. Data structure extension for "Scint", "Cher" detector types:
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* nchan (int): number of channels (firing?)
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* chan (std::vector<int>) channel number
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* adc (std::vector<int>) unencoded pedestal subtracted ADC value
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* tdc_l (std::vector<int>) unencoded leading TDC value
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* tdc_t (std::vector<int>) unencoded trailing TDC value
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h4. Data structure extension for "FADC" (HCal) detector types:
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* nchan (int): number of channels (firing?)
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* chan (std::vector<int>) channel number
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* samp (std::vector<int>) sample number
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* adc (std::vector<int>) unencoded pedestal subtracted ADC values for individual samples 
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* tdc (std::vector<int>) unencoded TDC value (optional: only for HCal at the moment)
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h4. Data structure extension for "GEMs" detector types:
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* nstrips (int) number of strips (firing?)
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* module (std::vector<int>) module number
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* strips (std::vector<int>) strip number
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* samp (std::vector<int>) sample number
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* adc (std::vector<int>) unencoded pedestal subtracted ADC values for individual samples