eic_endcap_insert

Getting started

Enter the EIC container (installation instructions) and go to the directory containing your EIC container (if not already there).

Installation instructions

Get the archived ip6 files and install them:

git clone https://github.com/eic/ip6.git
cd ip6
mkdir build && cd build
cmake .. -DCMAKE_INSTALL_PREFIX=$EIC_SHELL_PREFIX
make install -j8
cd ../..

Then clone this repository and install it:

git clone https://github.com/rymilton/eic_endcap_insert.git
cd eic_endcap_insert
mkdir build && cd build
cmake .. -DCMAKE_INSTALL_PREFIX=$EIC_SHELL_PREFIX
make install -j8
cd ..

Make sure IP6 and this repository have the same install prefix.

Editing the simulation

By default, the endcap simulation includes the HCal insert (W/Sc + Steel/Sc), ECal insert (homogeneous W/ScFi material), HCal (ATHENA: 20/3 mm Steel/Sc), ECal (homogeneous W/ScFi material), and the beampipe. To change what detectors are simulated, simply comment out the undesired ones in xml/endcapP_insert.xml.

Some simple parameters for the geometry are contained in compact/configuration_default.xml. If you want to simulate the endcap without a beampipe and hole, replace <include ref="compact/configuration_default.xml"/> with <include ref="compact/configuration_nohole.xml"/> and comment out <include ref="ip6/central_beampipe.xml"/> in xml/endcapP_insert.xml.

There is also a ZDC geometry in xml/zdc.xml.

NOTE: If you adjust any files, you need to make install in your build directory before running the simulation.

NOTE: If you remove any detector components from the endcapP_insert simulation, you must also comment out the related lines in scripts/endcapP_insert_reco.py and re-install.

Running the simulation

Before running any scripts, make sure you source the setup script:

source $EIC_SHELL_PREFIX/insert_setup.sh

This will create some simple environment variables used in the scripts. The DETECTOR variable in the script should correlate to the XML file you want to use.

You must source this script every time you enter the EIC container.

scripts/run_sim_hepmc.sh generates a HepMC file and feeds it to npsim and DD4hep. The resulting sim file is then sent through Juggler for digitization and reconstruction. The sim and reco files are saved. There are separate reconstruction scripts for the endcapP_insert and zdc geometries. Make sure your $DETECTOR variable is correct in in $EIC_SHELL_PREFIX/insert_setup.sh to use the correct script.

Some basic, adjustable paramaters are listed at the top of scripts/run_sim_hepmc.sh. There are also in-line options to choose the particle (-part or --particle), particle momentum/energy (-p or --momentum), and the number of events to be simulated (-n or --nevents). There is also a help option (-h or --help).

To run the simulation, use $SCRIPTS_PATH/run_sim_hepmc.sh.

Example:

$SCRIPTS_PATH/run_sim_hepmc.sh -part "pi-" -n 100 -p 10

uses 10 GeV pi- with 100 events.

There is a similar script, scripts/run_sim_gps.sh, with the same options that generates events using the General Particle Source (GPS) instead of the HepMC generator. See more about the GPS at the bottom of the README.

scripts/loop_energies.sh simulates multiple energies in a row. There are options for particle type and number of events, as well as the ability to choose the GPS or HepMC generator.

Output

There will be two output files: a sim file and a reco file. The sim file contains the Geant4 level information while the reco file contains the digitized and reconstructed information. Both contain information about the MCParticles. As a collaboration, we typically use the branches ending in HitsReco.

Addressing Homogenous ECal

To avoid high memory usage, the ECal and ECal insert use a mixed material of W/Polystyrene where the weight percentages are calculated based on the empirical weight and density of a prototype W/ScFi ECal. To incorporate the sampling fraction of the W/ScFi, a smearing procedure is needed: $E_{tower} = \mathrm{gRandom->Gaus}\left(E_{tower}*.03, \sigma\right)$, where $\sigma = E_{tower}\sqrt{a^2/E_{tower} + b^2}$, $a = 0.1$, and $b = 0.0015$. $\mathrm{gRandom}$ here is ROOT's random generator. This maintains the mean of W/ScFi and reproduces fluctuations with a random Gaussian. See this presentation (especially slide 3) by Zhiwan Xu, et al. for more details.

Images of simulation geometry

Whole endcap:

Front of HCal and insert:

W/Steel insert:

GPS documentation

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If you want to adjust the particle gun, here's the documentation for the general particle source (GPS):

Manual: https://www.fe.infn.it/u/paterno/Geant4_tutorial/slides_further/GPS/GPS_manual.pdf

Examples: https://hurel.hanyang.ac.kr/Geant4/Geant4_GPS/reat.space.qinetiq.com/gps/examples/examples.html