HepSim ca be used o create ROOT files after fast detector simulation, or one can analyse events after the Delphes fast simulation program on the fly. The latter approach allows to make changes to the detector geometry by the end-users and, at the the same time, perform an analysis. The output ROOT file only includes histograms defined by the user (but you can also add custom ROOT tree). To do this, use the FastHepSim package that includes Delphes-3.2.0 and ProMC 1.5, as well as an example analysis program. You can find a description of the current HCAL studies that use such an approach.

Follow these steps:

wget http://atlaswww.hep.anl.gov/asc/hepsim/soft/FastHepSim.tgz
tar -zvxf FastHepSim.tgz
cd FastHepSim/libraries/
./install.sh

This installs “FastHepSim” which includes Delphes, ProMC and hs-tools to work with HepSim. Then setup the environment

cd .. # go to the root directory
source setup.sh

Next, go to the analysis example:

cd analysis
make

This compiles the analysis program (analysis.cc) that fills jetPT and muonPT histograms. Now we need to bring data from HepSim and put them somewhere. For this example, we will copy data to the “data” directory:

hs-get http://mc.hep.anl.gov/asc/hepsim/events/pp/100tev/higgs_ttbar_mg5 data 2 3

This copies 3 files in 2 threads and put them to the directory “data”. Now we are ready to run over these 3 files:

./Make_input data  # creates inputdata.txt
./analysis delphes_card_FCC_basic_notau.tcl histo.root inputdata.txt

The first command creates a file “inputdata.txt” with input data. Then the program “analysis” reads the configuration file, data and generates “histo.root” with output histograms. This example uses “delphes_card_FCC_basic_notau.tcl” Delphes configuration file describing a basic FCC detector geometry. Note that we have removed tau tagging since we run over slimmed events with missing mothers of particles.

If you want to access other objects (photons, electrons, b-jets), use Delphes definitions of arrays inside the source code “analysis.cc”. You can put external files into the src/ directory where it will be found by Makefile.

If you still want to look at the event structure in the form of ROOT tree, run the usual Delphes command:

../libraries/Delphes/DelphesProMC  delphes_card_FCC_basic_notau.tcl  output.root data/mg5_Httbar_100tev_001.promc

where output.root will contain all reconstructed objects. In this case, add “TreeWriter” after “ScalarHT”. If the input file contains complete (non-slimmed) record, one can add “tau” reconstruction (“TauTagging” line).

Try also more sophisticated detector-geometry cards:

• examples/delphes_card_Snowmass_NoPileUp.tcl - similar to Snowmass 2013. It has CA (fat) jets and B-tagging
• examples/delphes_card_ATLASLIKE.tcl - similar to ATLAS detector (comes with Delphes)

Note that “TreeWriter” module should be enabled when creating ROOT files, and disabled when using analysis mode.

Here we describe how to make fast detector simulation files using separate external libraries, without installing FastHepSim. Use the Delphes fast detector simulation program to process the MC events. Delphes can read ProMC files directly. First, make sure that ProMC and ROOT library is installed:

echo $PROMC $ROOTSYS

This should point to the installation paths of ProMC and ROOT.

Here are the steps to perform a fast detector simulation using ProMC files from the HepSim repository:

1) Download Delphes-3.2.0.tar.gz (or higher) and compile it as:

wget http://cp3.irmp.ucl.ac.be/downloads/Delphes-3.2.0.tar.gz
tar -zvxf Delphes-3.2.0.tar.gz
cd Delphes-3.2.0
./configure
make

This creates the converter “DelphesProMC” (among others), if “PROMC” environmental variable is detected.

2) For FCC studies, copy and modify the detector configuration file “delphes_card_FCC_basic.tcl”

cp cards/delphes_card_FCC_basic.tcl delphes_card_FCC_notau.tcl

Then remove the line “TauTagging”. Do the same when using the card “cards/delphes_card_ATLAS.tcl” (for ATLAS). We do not use the tau tagging module since it requires complete event records with all mother particles. Since ProMC files are often slimmed by removing some unstable low pT particles and showered partons, Delphes will fail on this line. If you need tau tagging, please use ProMC files with complete particle record.

3) Download Monte Carlo files from the 100 HepSim repository. For example, get a file with 5000 ttbar events generated for a 100 TeV collider:

wget http://mc.hep.anl.gov/asc/hepsim/events/pp/100tev/ttbar_mg5/mg5_ttbar_100tev_001.promc

and then create a ROOT file with reconstructed objects after a fast detector simulation (FCC detector):

./DelphesProMC delphes_card_FCC_notau.tcl  mg5_ttbar_100tev_001.root mg5_ttbar_100tev_001.promc

The conversion typically takes 30 seconds.

Currently, the full detector simulation can be done using the SLIC software. You will need to convert ProMC files to LCIO files and use these files for the “sclic” Geant4-based program.

The physics performance studies are listed here. They are based on Jas4pp program.

How to convert ProMC to LCIO files is described in converting_to_lcio

One can mix events from a signal ProMC file with inelastic (minbias) events using a “pileup” mixing program:

hs-pileup pN signal.promc minbias.promc output.promc

Here “p” indicates that N events from minbias.promc will be mixed with every event from signal.promc using a Poisson distribution. If “p” is missing, then exactly N events from minbias.promc will be mixed with single event from signal.promc. Use large number of events in minbias.promc to minimise reuse of the same events from the minbias.promc. The barcode of particles inside output.promc indicates the event origin.

Here is an example to create events with pileup for the paper http://arxiv.org/abs/1504.08042 Phys. Rev. D 91, 114018 (2015): We mix h→ HH signal file with MinBias Pythia8 (A2 tune) sample using <mu>=200 (Poisson mean):

wget http://atlaswww.hep.anl.gov/asc/hepsim/soft/hs-toolkit.tgz -O - | tar -xz;
source hs-toolkit/setup.sh
wget http://mc.hep.anl.gov/asc/hepsim/events/pp/100tev/minbias_a2_pythia8_l3/tev100_pythia8_MinBias_l3__A2_001.promc
wget http://mc.hep.anl.gov/asc/hepsim/events/pp/100tev/s0higgshiggs_alltau/tev100_s0higgshiggs_alltau_0001.promc
hs-pileup p200 tev100_s0higgshiggs_alltau_0001.promc tev100_pythia8_MinBias_l3__A2_001.promc output.promc 

Look at the “output.promc” with the browser to see how events are filled. Now you can use DELPHES to create fast simulation files using events with pileup.

Note: pileup mixer is implemented in Java, therefore it uses 64bit zip. For C++ programs, please use ProMCBook(“file.promc”, “r”, true) to open ProMC files (notice “true” as a new argument). For example, for the Delphes program, change the line

inputFile = new ProMCBook(argv[i], "r");       # 32bit zip

in readers/DelphesProMC.cpp to

inputFile = new ProMCBook(argv[i], "r", true); # 64bit zip

A file can be reduced in size by extracting N events as this:

hs-extract signal.promc N

where signal.promc is the original file, and N is the number of events to extract.

HepSim maintains analysis scripts that can be used for comparing Monte Carlo simulations with data from Durham HepData database. For example, click the link with AAD 2013 (Search for new phenomena in photon+jet events collected in proton–proton collisions at sqrt(s) = 8 TeV with the ATLAS detector) paper

• Navigate to “DataMelt” and use right-mouse and select “Copy link location”
• Start DMelt if you did not yet, and select [File]-[Read script from URL]. Copy and paster the URL link from the HepData database
• Click “run”.

HepData maintain Jython scripts that use the same syntax as HepSim. You can start from a HepSim validation script, and before the “export” command, append the scripts with data from Durham HepData database. Or you can start from a HepData “SCaVis” script and add parts from HepSim validation script that reads data from HepSim. Note that SCaVis and DMelt are equivalent.

There are several methods to create ProMC files from MC simulations. The most complete description is given here. Here are several examples:

• If you use Pythia8, look at the example “main46.cc” inside Pythia8 package.
• For other generators, such as Herwig++ and Madgraph, write events in either lhe files or hepmc files. Then use the converters “stdhep2promc” or “hepmc2promc” that are shipped with ProMC (inside $PROMC/examples).

If are working on a description of how to fill ProMC files from Jetphox or MCFM. At this moment, contact us to get help.

We have very limited support for other formats, since they are typically 1) large files (such as HEPMC); 2) cannot be used for streaming over the network; 3) are not suited in a multi-platform environments (i.e. Windows).

For ANL cluster, you do not need to install Delphes. Simply run the reconstruction as:

source /share/sl6/set_asc.sh
$DELPHES/DelphesProMC delphes_card_FCC_notau.tcl mg5_ttbar_100tev_001.root mg5_ttbar_100tev_001.promc

The cards are located in $DELPHES/examples.

If you want to run over multiple ProMC files without manual download, use this command:

java -cp hepsim.jar hepsim.Exec DelphesProMC delphes.tcl output.root [URL] [Nfiles]

where [URL] is HepSim location of files and [Nfiles] is the number of files for processing. The output ROOT will be located inside the “hepsim_output” directory. Here is a small example:

java -cp hepsim.jar hepsim.Exec DelphesProMC delphes.tcl output.root  http://mc.hep.anl.gov/asc/hepsim/events/pp/100tev/higgs_ttbar_mg5 5

which processes 5 files from Higgs to TTbar sample. Skip “5” at the end to process all files.

ProMC files with single particles can be created using the ProMC. Download the recent ProMC package and look at the directory:

wget http://atlaswww.hep.anl.gov/asc/promc/download/current.php -O ProMC.tgz
tar -zvxf ProMC.tgz
cd examples/particle_gun
source setup.sh
javac promc_gun.java
java promc_gun pions.promc 100 211 1000 # E=0-100 GeV, PID=211, events=1000

This creates file “pions.promc” with 2 particles per event, with the maximum energy of 100 GeV (randomly distributed from 0 to 100). The particles are pions (pi+, pid=211). The total number of events 1000. The phi and theta distributions are flat After file creation, look at the events using the file browser. You can also modify the java code to change the single-particle events.

ProMC files can be converted to LCIO files for full detector simulation. This is an example of such conversions:

wget http://atlaswww.hep.anl.gov/asc/promc/download/current.php -O ProMC.tgz
tar -zvxf ProMC.tgz
cd examples/promc2lcio
source setup.sh
javac promc2lcio.java
java promc2lcio file.promc file.slcio

Look at other directories in “examples/”. You can convert ProMC files to many other formats (most converters require installation of the ProMC C++ package).

Particle records from the generators based on LO/NLO+parton showers calculations (PYTHIA, HERWIG, MADGRAPH) are often “slimmed” to reduce file sizes. In the case when records are slimmed, the following algorithm is used:

(status=1 && pT>0.3 GeV ) or   # keep final states with pT>0.3 GeV 
(PID=5 || PID=6)  or           # keep b or top quark 
(PID>22 && PID<38)  or         # keep exotics and Higgs
(PID>10 && PID<17)  or         # keep all leptons and neutrinos 

where PID is absolute value of particle codes. Leptons ane neutrinos are also affected by the slimming pT cut. Note: for 100 TeV collisions, the pT cut is increased from 0.3 to 0.4 GeV. For NLO calculations with a few partons + PDF weights, the complete event records are stored.

In the case when the slimming is applied, file sizes are reduced by x2 - x3. In some situation, slimming can affect detector simulation. For example, you should turn of tau reconstruction in Delphes when slimming is used.