Table of Contents

Calorimeter studies using a fast simulation

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 this manual. To simplify the setup, we have prepared a package that includes Delphes, ProMC and HS-TOOLs. Follow these steps: 

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

If installed correctly, setup the environment: 

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

Next, go to the analysis code and compile it: 

cd analysis
make

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: 

examples/hcal/fcc_towers.tcl

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:

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

# 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

Electrons and photons (pi0!) do not leak to HCAL.

0.05(eta) cells

This card: 

examples/hcal/fcc_towers_eta05.tcl

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: 

# 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

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: 

examples/hcal/fcc_towers_eta025.tcl

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: 

# 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

0.05(eta)x0.05(phi) cells

This card: 

examples/hcal/fcc_towers_eta05phi05.tcl

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: 

# 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

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: 

examples/hcal/fcc_towers_eta025phi025.tcl

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: 

# 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

This segmentation has similar angle in phi and eta.

How to run

We need to bring truth-level data from HepSim and put them somewhere. We will use 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: 

hs-get http://mc.hep.anl.gov/asc/hepsim/events/pp/100tev/ttbar_pt2500_mg5  data 2 10

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: 

./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

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 mass.py script. This will show 2 jets masses for boosted top for different HCAL segmentation.

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: 

./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

To make plot, again run mass.py script.

Now let's try to run using “eFlow” cards:

Next steps

Try several physics channels:

— Sergei Chekanov 2014/11/11 14:16