afterburner

EIC MC afterburner.

Installation

The converter and benchmark require libyaml-cpp. Those are available in package managers for the most of systems:

apt install libyaml-cpp-dev     # Debian/Ubuntu/Mint
yum install yaml-cpp-devel      # RHEL/CentOS/Fedora

git clone https://eicweb.phy.anl.gov/monte_carlo/afterburner.git
mkdir -p afterburner/build
cd afterburner/build

# setup cmake (c++ code lives in cpp directory) 
cmake ../cpp

# to build all
cmake --build ../cpp --target all

# to install
cmake --build ../cpp --target install -- -j 8

Preinstalled versions are available in ATHENA containers.

CLI command

Examples:

# Process my whole file, add crossing angle, beam effects, do validation plots
abconv my.hepmc

# Same, but limit the number of events to 1000 and set the output name as 'test'
abconv my.hepmc -o test -l 1000

# Just convert hepmc3 to hepmc2 don't use afterburner, don't create plots
abconv my.hepmc -f hepmc2 --ab-off --plot-off 

How exactly the afterburner works illustrated by abconv my.hepmc command.

• AB opens my.hepmc file, gets beam particles and extract beam energy settings

  • The settings should correspond to one of EIC beam energy setups:
    • ep [GeV]: 275x18, 275x10, 100x10, 100x5, 41x5
    • eAu [GeV]: 110x18, 110x10, 110x5, 41x5
  • (!) Thus the input file must have two beam particles (marked by status code 4)
  • One can see available settings that correspond to EIC CDR tables 3.3, 3.4, 3.5
  • Using -c/--config flag one can select a profile:
    • 0: High Divergence (default),
    • 1: High Acceptance
    • 2: eAu

• AB awaits that there is no crossing angle between beam particles. To check this AB calculates a crossing angle between beams of the first event. If the crossing angle is not zero and --exit-ca flag is set - AB exits; without the flag a warning is issued.

• AB processes events applying crossing angle and beam effects for each event.

  • -s,--ev-start, -e,--ev-end, -l,--limit - limits the number of events to process

• By defaults AB also creates *.hist.root file that contains validation histograms

  • --plot-off flag can switch off histograms creation

Options:

(1) How --exit-ca works exactly: when afterburner processes the first event it checks if it has 2 beam particles (fails with non zero code if not) and then calculates their crossing angle with the --exit-ca is set and crossing angle absolute value is > 1mrad program ends with 0 code. This method is very coarse as if in a source file the crossing angle is 0 but all beam effects do exist, beam effects will be applied twice

Validation

To apply benchmarks. Head-on data (no crossing angle nor effects) is located:

https://dtn01.sdcc.bnl.gov:9000/minio/eictest/ATHENA/WG/BeamEffects/

Pythia8 generated data with crossing angle and full effects is located:

https://dtn01.sdcc.bnl.gov:9000/minio/eictest/ATHENA/EVGEN/DIS/NC/

The validation plots are generated and can be viewed in python/comparison.ipynb

Essential plots from the latest validation run:

The discrepancy in low Eta has been explained by a slight phase space difference in generated headon and full beam effects files on Pythia8 side. TL;DR; It is Fine

41x5 GeV	100x10 GeV	275x18 GeV

References

• Accelerator and beam conditions critical for physics and detector simulations for the Electron-Ion Collider
• Pythia8 beam effects
• Fun4All code