2023 KLF Simulations

Installing Software

The reconstruction and analysis software are built on the same software stack used for the analysis of photon beam measurements with the GlueX detector.

• You can find some general information on GlueX software and computing at this page.
• A general overview of the GlueX software can be found here.

There are a couple of different ways to install the GlueX software stack.

• You can follow these instructions to build the full software stack locally.
• Or you can run the GlueX software in a container.

Note that the GlueX software installation has been verified to work on RedHat/CentOS 7 and various Ubuntu versions - basically anywhere you can install the scons package. Instructions exist on how to install on RedHat/CentOS 8, link to them. The software currently does not build under RedHat/CentOS 9 - you are better off running the software inside a container in this case, for now.

You can then install the KLF-specific branches using the my_halld_update.py script from the build_scripts package, and the XML configuration file given below, e.g., my_halld_update.py -x /path/to/version.klf.xml.

Example version.klf.xml configuration file (Click "Expand" to the right for more details -->):

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="https://halldweb.jlab.org/halld_versions/version7.xsl"?>
<gversions file="version_5.11.0.xml" date="2023-06-14">
<package name="amptools" version="0.14.5"/>
<package name="ccdb" version="1.06.09"/>
<package name="cernlib" version="2005" word_length="64-bit"/>
<package name="diracxx" version="2.0.2"/>
<package name="evio" version="4.4.6"/>
<package name="evtgen" version="01.07.00"/>
<package name="geant4" version="10.04.p02"/>
<package name="gluex_MCwrapper" version="v2.7.0"/>
<package name="gluex_root_analysis" version="1.24.0" dirtag="hdr441"/>
<package name="halld_recon" branch="sdobbs_klong_beam"/>
<package name="halld_sim" version="4.45.0"/>
<package name="hdds" version="4.15.0"/>
<package name="hdgeant4" version="2.35.0" dirtag="hdr441"/>
<package name="hd_utilities" version="1.45"/>
<package name="hepmc" version="2.06.10"/>
<package name="jana" version="0.8.2" dirtag="ccdb169"/>
<package name="lapack" version="3.9.0"/>
<package name="photos" version="3.61"/>
<package name="rcdb" version="0.07.01"/>
<package name="root" version="6.24.04"/>
<package name="sqlitecpp" version="3.1.1"/>
<package name="sqlite" version="3.36.0" year="2021"/>
<package name="xerces-c" version="3.2.3"/>
</gversions>

A version of the dedicated KLF event generator can be downloaded and installed from here https://github.com/sdobbs/KLGenerator_hddm_V3 using the following commands:

git clone https://github.com/sdobbs/KLGenerator_hddm_V3
cd KLGenerator_hddm_V3
scons install

Note that KLGenerator_hddm_V3 is installed under $HALLD_MY/bin, so make sure that you have that directory in your PATH.

Generating Events

The KLGenerator_hddm_V3 program has some good online help through the -h switch.

For an example, let's try generating 1M KL p -> Ks p events.

KLGenerator_hddm_V3 -M100 -Fgenerated.root -Ekaon:histo:1.0:4.0 -Rkl2

This writes events out to a file named generated.hddm.

Here are some useful/interesting switches to consider for these studies:

• -t - disables KL beam propagation calculation - this basically forces hdgeant4 to treat this as a photon beam reaction
• -c - disables simulation of KPT z size, so all KLs are produced exactly 24 m from the target center.

Note that right now all events are generated in the center of the LH2 target (z=65 cm). I'm working on updating this.

There are two next steps: running the events through the GEANT4-based detector simulation, and applying the detector response. When running all of these pieces of software, the following environment variable must be set to the following value: JANA_CALIB_CONTEXT variation=mc.

The GEANT4-based simulation package is called hdgeant4. It relies on a configuration file called control.in. There is some thorough documentation at this location, however, you can find a simple control.in file to start out with below.

Example control.in file

(Click "Expand" to the right for more details -->):

INFILE 'generated.hddm'
TRIG 10
RUNG 30730
OUTFILE 'hdgeant4_output.hddm'
TOFMAX 1e-5
HADR 1
CKOV 1
LABS 1

You can then run the program as, for example, hdgeant4 -t6 (the -t6 says to run with 6 threads - please change this to whatever is convenient to your system). The output is then saved as hdgeant4_output.hddm.

You can apply the detector smearing then by running the command mcsmear hdgeant4_output.hddm. The output file will then be hdgeant4_output_smeared.hddm.

Next steps

Finish implementing standard ROOT tree output.

Determine some loose default TOF PID selections.

Implement KL beam into the kinematic fitting framework