====== Calorimeter studies using a fast simulation ======

[[http://atlaswww.hep.anl.gov/hepsim/ | HepSim]] repository provides a number of truth-level MC samples for signal and background that can be used as inputs for a fast simulation. The analysis can be done as explained in  [[https://atlaswww.hep.anl.gov/asc/wikidoc/doku.php?id=community:refhepsim |this manual]]. 
To simplify the setup, we have prepared a package that includes [[https://cp3.irmp.ucl.ac.be/projects/delphes | Delphes]], [[http://atlaswww.hep.anl.gov/asc/promc/ | ProMC]] and HS-TOOLs. 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>
If installed correctly, setup the environment:

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

Next, go to the analysis code and compile it:

<code bash>
cd analysis
make
</code>

This compiles the analysis program (analysis.cc) that fills pT and jet mass histograms. Before running this program, we will describe what detector geometry can be studied. They are explained in the sections below.

===== ATLAS-like geometry =====

This card:
<code>
examples/hcal/fcc_towers.tcl
</code>

Creates jets from "combined towers", i.e. from HCAL and ECAL towers.  This card also apples a simple scale correction for jets  1.06+400/(pt*pt*) (this was done after a study of jet resolution plots). 

For the initial test, we assume the following segmentation:

  * HCAL has 64 modules in Phi and Eta=0.1 in the central region
  * ECAL has  x4 better segmentation
  * 60% of energy of charged pions and all baryons are in HCAL 

This  HCAL geometry has a well balanced segmentation in 2D (same angle of 5.625 deg in Phi and Theta).

<code bash>
# ECAL:
# ----
#   -1.6<Eta<1.6.                      Segment: 0.025 eta x 1.40625 deg phi  
#   -4.5<Eta<-1.7 and 1.7<Eta<4.5      Segment: 0.05  eta x 10 deg phi  
#   -6.0<Eta<4.6      and 4.6<Eta<6    Segment: 0.2 eta x 20 deg phi
# 
# HCAL (64 modules in Phi):
# ----
#   -1.6<Eta<1.6.                      Segment: 0.1 eta x 5.625 deg phi  
#   -4.5<Eta<-1.7 and 1.7<Eta<4.5      Segment: 0.2 eta x 11.25 deg phi  
#   -6.0<Eta<4.6      and 4.6<Eta<6    Segment: 0.2 eta x 20 deg phi
</code>
Electrons and photons (pi0!) do not leak to HCAL.  


===== 0.05(eta) cells =====

This card:
<code bash>
examples/hcal/fcc_towers_eta05.tcl
</code>

It is similar to the ATLAS-like, but eta has x2 better segmentation in eta (0.05). Phi is the same as before.
ECAL also did not change. The geometry has the following segmentation:


<code bash>
# ECAL:
# ----
#   -1.6<Eta<1.6.                      Segment: 0.025 eta x 1.40625 deg phi  
#   -4.5<Eta<-1.7 and 1.7<Eta<4.5      Segment: 0.05  eta x 5.625   deg phi  
#   -6.0<Eta<4.6      and 4.6<Eta<6    Segment: 0.2 eta x 10        deg phi
# 
# HCAL (64 modules in Phi):
# ----
#   -1.6<Eta<1.6.                      Segment: 0.05 eta x 5.625  deg phi  
#   -4.5<Eta<-1.7 and 1.7<Eta<4.5      Segment: 0.2 eta x 11.25   deg phi  
#   -6.0<Eta<4.6      and 4.6<Eta<6    Segment: 0.2 eta x 20 deg  phi
</code>

Note: In this case, segmentation in terms of the polar angle is x2 better  (2.864 deg) than in terms of phi angle (5.625 deg).

=====  0.025(eta) cells=====

This card:
<code bash>
examples/hcal/fcc_towers_eta025.tcl
</code>

It is similar to the ATLAS-like, but eta has x4 better segmentation (0.025). Phi is the same.
The geometry has the following segmentation:


<code bash>
# HCAL (64 modules in Phi):
# ----
#   -1.6<Eta<1.6.                      Segment: 0.025 eta x 5.625 deg phi  
#   -4.5<Eta<-1.7 and 1.7<Eta<4.5      Segment: 0.2 eta x 11.25 deg phi  
#   -6.0<Eta<4.6      and 4.6<Eta<6    Segment: 0.2 eta x 20 deg phi
</code>

===== 0.05(eta)x0.05(phi) cells =====

This card:
<code bash>
examples/hcal/fcc_towers_eta05phi05.tcl
</code>

It is similar to the ATLAS-like, but eta has x2 better segmentation in Eta(0.05) and Phi (5.625/2). 
This option has similar angular segmentation in Eta and Phi (~2.8 degree)
The geometry has the following segmentation:

<code bash>
# HCAL (64 modules in Phi):
# ----
#   -1.6<Eta<1.6.                      Segment: 0.05 eta x 5.625/2 deg phi  
#   -4.5<Eta<-1.7 and 1.7<Eta<4.5      Segment: 0.1 eta x 11.25 deg phi  
#   -6.0<Eta<4.6      and 4.6<Eta<6    Segment: 0.2 eta x 20 deg phi
</code>

This geometry has similar segmentation in terms of polar angle. (0.05 corresponds to 2.864 deg, and this is the same as the phi segmentation)

=====  0.025(eta)x0.025(phi) cells =====

This card:
<code bash>
examples/hcal/fcc_towers_eta025phi025.tcl
</code>

It is similar to the ATLAS-like, but eta has x4 better segmentation in Eta (0.025) and Phi (1.40625 deg). 
This is another example of a good angular segmentation in 2D (~ 1.4 deg).
The geometry has the following segmentation:


<code bash>
# HCAL (64 modules in Phi):
# ----
#   -1.6<Eta<1.6.                      Segment: 0.1/4 eta x 5.625/4 deg phi  
#   -4.5<Eta<-1.7 and 1.7<Eta<4.5      Segment: 0.2/2 eta x 11.25/2 deg phi  
#   -6.0<Eta<4.6      and 4.6<Eta<6    Segment: 0.2 eta x 20 deg phi
</code>

This segmentation has similar angle in phi and eta.

===== How to run =====

We need to bring truth-level data from [[http://atlaswww.hep.anl.gov/hepsim/| HepSim]] and put them somewhere. 
We will use [[https://atlaswww.hep.anl.gov/hepsim/info.php?item=57 | TTBar sample]] generated with pT>2.5 TeV and look at the jet mass.
Go to "analysis" directory and copy a few truth-level files:
<code bash>
hs-get http://mc.hep.anl.gov/asc/hepsim/events/pp/100tev/ttbar_pt2500_mg5  data 2 10
</code>
This copies 10 files in 2 threads and put them to the directory "data". Now we are ready to run over these 10 files.

Let us make 2 runs: One run  will use the first geometry layout, and the second run will use the 2nd input card.
We will do fast a simulation on the fly using antiKT5 jets and  pT(jet)>2.5 TeV:

<code bash>
./Make_input data  # creates inputdata.txt
./analysis  examples/hcal/fcc_towers.tcl             histo1.root inputdata.txt
./analysis  examples/hcal/fcc_towers_eta05phi05.tcl  histo2.root inputdata.txt
</code>

The first command creates a file "inputdata.txt" with input data. 
Then the program "analysis" reads the configuration file, truth-level data and generates "histo1.root"
with output histograms. 

To make plot, run {{:vlhc:mass.py|}} script. This will show 2 jets masses for boosted top  for different HCAL segmentation.



{{:vlhc:mass_towers.eps.png?400|}}


Note: the eflow option has much better resolution for jet masses.

===== Using particle flows (eFlow) =====


You can also use particle flows in the same way. Just replace "towers" by "eflow" in the name of input card.
Examples when using eflows:

<code bash>
./Make_input data  # creates inputdata.txt
./analysis  examples/hcal/fcc_eflow.tcl             histo1e.root inputdata.txt
./analysis  examples/hcal/fcc_eflow_eta05phi05.tcl  histo2e.root inputdata.txt
</code>


To make plot, again run {{:vlhc:mass.py|}} script. 


Now let's try to run using "eFlow" cards:

{{:vlhc:mass_eflow.eps.png?400|}}

{{:vlhc:tau32_eflow.eps.png?400|}}

===== Next steps =====


  * Change energy fractions for HCAL and ECAL (say, 70% goes to HCAL and 30 to ECAL). I do not know how to make energy dependent fractions.

Try several physics channels:

  * Higgs to bbar. Look at the mass resolution of 2 b-jets and make Higgs mass. Use the sample [[http://atlaswww.hep.anl.gov/hepsim/info.php?item=79]]
  * Exited fermions.  Look at the mass resolution of 2 jets from q*. Use the sample [[http://atlaswww.hep.anl.gov/hepsim/info.php?item=81]]
  * Boosted top. Look at the jet mass (should give top mass). Use the sample [[http://atlaswww.hep.anl.gov/hepsim/info.php?item=22]]
  * Inclusive jets: look at jet pT resolution. Look at [[https://atlaswww.hep.anl.gov/hepsim/info.php?item=13]].

 --- //[[chekanov@anl.gov|Sergei Chekanov]] 2014/11/11 14:16//