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===== Creating Delphes files  =====

Here we describe how to make fast detector simulation files 
using separate external libraries, without installing FastHepSim.
Use the [[https://cp3.irmp.ucl.ac.be/projects/delphes | Delphes]] fast detector simulation program to process the MC events. Delphes can read [[http://atlaswww.hep.anl.gov/asc/promc/ | ProMC]] files directly. First, make sure that ProMC and ROOT library is installed:
<code bash>
echo $PROMC $ROOTSYS
</code>
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 [[http://cp3.irmp.ucl.ac.be/downloads/Delphes-3.3.0.tar.gz | Delphes-3.3.0.tar.gz]] (or higher) and compile it as: 
<code bash>
wget http://cp3.irmp.ucl.ac.be/downloads/Delphes-3.2.0.tar.gz
tar -zvxf Delphes-3.3.0.tar.gz
cd Delphes-3.3.0
./configure
make
</code>
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" 
<code bash>
cp cards/delphes_card_FCC_basic.tcl delphes_card_FCC_notau.tcl
</code>
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 [[ http://mc.hep.anl.gov/asc/hepsim/events/?dir=pp/100tev | 100 HepSim repository]].
For example, get a file with 5000 ttbar events generated for a 100 TeV collider:
<code bash>
wget http://mc.hep.anl.gov/asc/hepsim/events/pp/100tev/ttbar_mg5/mg5_ttbar_100tev_001.promc
</code>

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

<code bash>
./DelphesProMC delphes_card_FCC_notau.tcl  mg5_ttbar_100tev_001.root mg5_ttbar_100tev_001.promc
</code>
The conversion typically takes 30 seconds.


===== On the fly reconstruction =====
HepSim can be used to create ROOT (Delphes) files 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 [[http://atlaswww.hep.anl.gov/asc/hepsim/soft/FastHepSim.tgz| FastHepSim package]]
that includes [[http://cp3.irmp.ucl.ac.be/downloads/Delphes-3.2.0.tar.gz | Delphes-3.2.0]] and ProMC 1.5, as well as an example analysis program.
You can find a description of the [[https://atlaswww.hep.anl.gov/asc/wikidoc/doku.php?id=vlhc:hcal|current HCAL studies]] that use such an approach.

Follow these steps:

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

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

<code bash>
cd .. # go to the root directory
source setup.sh
</code>

Next, go to the analysis example:

<code bash>
cd analysis
make
</code>
 
This compiles the analysis program (analysis.cc) that fills jetPT and muonPT histograms. 
Now we need to bring  data from [[http://atlaswww.hep.anl.gov/hepsim/| HepSim]] and put them somewhere. For this example,
we will copy data to the "data" directory:

<code bash>
hs-get http://mc.hep.anl.gov/asc/hepsim/events/pp/100tev/higgs_ttbar_mg5 data 2 3
</code>
This copies 3 files in 2 threads and put them to the directory "data". Now we are ready to run over these 3 files:

<code bash>
./Make_input data  # creates inputdata.txt
./analysis delphes_card_FCC_basic_notau.tcl histo.root inputdata.txt
</code>

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 [[https://cp3.irmp.ucl.ac.be/projects/delphes/wiki/WorkBook/Arrays | 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:
<code bash>
../libraries/Delphes/DelphesProMC  delphes_card_FCC_basic_notau.tcl  output.root data/mg5_Httbar_100tev_001.promc
</code>
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.













====== A note for ANL cluster  ======

For ANL cluster, you do not need to install Delphes. Simply run the reconstruction as:
<code bash>
source /share/sl6/set_asc.sh
$DELPHES/DelphesProMC delphes_card_FCC_notau.tcl mg5_ttbar_100tev_001.root mg5_ttbar_100tev_001.promc
</code>
The cards are located in $DELPHES/examples.

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

<code bash>
java -cp hepsim.jar hepsim.Exec DelphesProMC delphes.tcl output.root [URL] [Nfiles]
</code>
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:
<code bash>
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
</code>
which processes 5 files from [[http://atlaswww.hep.anl.gov/hepsim/info.php?item=2|Higgs to TTbar sample]]. 
Skip "5" at the end to process all files. 



====== Record slimming ======
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:

<code python>
(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 
</code>
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.
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