Parametric simulation

Talks

• Software meeting 2018-06-29, Friday, File:Sctau papas v2 20180629.pdf
• Workshop on future Super c-tau factories 2021-11-16 Parametric simulation of the SCT detector

SctParSim

A parametric simulation is a tool to receive a detector response without detailed description of interaction of particles with matter.

Implemented detector subsystems:

• drift chamber
• FARICH PID system
• calorimeter
• muon system

The parametric simulation yields the detector response in the SCT EDM format thus allowing to analyze its result in the same manner as the result of the full simulation.

How-to use the parametric simulation is demonstrated here

Detector configuration

The detector parameters can be changed in the run script (see Configuration section). The detector parameters and their default values can be viewed here.

SctParSimAlg

Name to change parameter	Description	Default value
B	Detector magnetic field	1.5
mostProbMass	The mass of most probable particle	0.13957

TrackSystemTool

Name to change paramater	Description	Default value
trackRhoMin	Inner radius of barrel tracker, m	0.1
trackRhoMax	Outer radius of barrel tracker, m	0.8
trackZMin	Inner z coordinate of endcup tracker, m	0
trackZMax	Outer z coordinate of endcup tracker, m	1
trackMinPt	Minimum momentum, GeV	0.05
trackPtProb	Registration probabilities for different momentum, {GeV, prob}	{{0.1, 0.8}, {0.3, 0.9}, {1, 0.95), {10, 0.99}}
trackRadLen	Radiation length in the track system, m	187
trackResParPT	Parameterizaton parameters for xy projection	0.00212
trackResParPZ	Parameterization parameters for z projection	{0.001281, 0.00308}
trackLayerAx	The radius of layers anf the location radius of the anod layers, mm	{{6.306, 217.306}, {6.644, 227.1}, {7.165, 246.906}, {6.564, 341.938}, {6.794, 352.06}, {7.14, 371.992}, {7.388, 382.95}, {6.651, 467.57}, {6.823, 477.718}, {6.968, 488.097}, {7.12, 498.701}, {7.274, 509.535}, {6.768, 636.322}, {6.898, 646.501}, {7.007, 656.957}, {7.121, 667.581}, {6.791, 750.730}, {6.902, 761.027}, {6.995, 771.472}, {7.091, 782.061}}
trackLayerSt	The radius of layers and the location radius of the stereo layers, mm	{{6.473, 280.136}, {6.747, 290.136}, {7.182, 310.863}, {7.486, 321.938}, {6.603, 405.941}, {6.799, 416.04}, {7.104, 436.741}, {7.314, 447.606}, {6.741, 533.35}, {6.859, 543.615}, {7.026, 554.088, {7.161, 564.762}, {6.778, 584.801}, {6.919, 595.108}, {7.039, 605.606}, {7.163, 6169.289}, {6.746, 689.948}, {6.865, 700.185}, {7.041, 720.09}, {7.165, 730.775}}

FARICHSystemTool

Name to change paramater	Description	Default value
farichRhoMin	Inner radius of barrel FARICH system, m	0.82
farichRhoMax	Outer radius of barrel FARICH system, m	0.9
farichZMin	Inner z coordinate of endcup FARICH system, m	1.02
farichZMax	Outer z coordinate of encup FARICH system, m	1.273
farichHoleR	Hole radius of FARICH system	0.3
parSimFarichFileName	The path to the file with response histograms of FARICH	./pi_ms_f1_mppc2_px3_d200_mla4_graph2d.root

CaloSystemTool

Name to change paramater	Description	Default value
caloRhoMin	Inner radius of barrel calorimeter, m	1.09
caloRhoMax	Outer radius of barrel calorimeter, m	1.55
caloZMin	Inner z coordinate of endcup calorimeter, m	1.293
caloZMax	Outer z coordinate of endcup calorimeter, m	1.86
caloCosthmax	Maximum cosine	0.9
caloClSize	Calorimeter cluster size, m	0.045
caloClSizeEGamma	Calorimeter cluster size for gamma, m	0.15
caloEMinBarrel	Minimal energy, GeV	0.015
caloEMinEndcup	Minimal energy, GeV	0.015
caloResPar	Parameterization parameters	{1.34e-2, 0.066e-2, 0.0, 0.82e-2}

MuonSystemTool

Name to change paramater	Description	Default value
muonRhoMin	Inner radius of barrel muon system, m	1.87
muonRhoMax	Outer radius of barrel muon system, m	2.15
muonZMin	Inner z coordinate of endcup muon system, m	1.88
muonZMax	Outer z coordinate of endcup muon system, m	2.16
parSimMuonFileNameMu	The path to the file with response histograms of muon system (muon)	./g4beamline_mu_plus_100k_parse.root
parSimMuonFileNamePi	The path to the file with response histograms of muon system (pion)	./g4beamline_pi_plus_100k_parse.root

Parameterization

Drift chamber

The track resolution is described here.

The parametric simulation has two options in the tracker to the particle identification: an ionisation clusters counting (dNcl/dx) and dE/dx. The model of calculation the specific number of ionization clusters is taken from a TraPID option by F. Gracagnolo (The presentation on "Joint Workshop on Future tau-charm factory" in December 4--7, 2018). An energy losing is calculated using the resolution model from BaBar experiment. The The $\sigma \left( \frac{dE}{dx} \right)$ is parameterized as

$\sigma \left( \frac{dE}{dx} \right) = \alpha \left( \frac{dE}{dx} \right) ^\beta dx^\gamma$

where α, β, γ is tuned on BaBar data.

• 

  Momentum resolution as a function of momentum depending on polar angle for π+

• 

  The dependence of the dE/dx on the momentum in the tracker system

• 

  The dependence of the specific number of ionization clusters on the momentum in the tracker system

FARICH PID system

The FARICH PID system works using the results of the full GEANT4 simulation. The system output is the particle speed and number of photons.

• 

  The dependence of the particle β factor on the momentum in the FARICH PID system

• 

  The dependence of the number of photoelectron on the βγ factor in the FARICH PID system for different angles (black - 10°, red - 30°, green - 45°)

Calorimeter

The calorimeter resolution is sigma_E = e0 + e1 / E + e2 / sqrt(E) + e3 / E^0.25, the coefficients (e0, e1 etc.) are taken from the D. Epifanov presentation on Super C-Tau factory workshop in May 27, 2018.

There are two cluster sizes to gammas / electrons and other particles.

Reconstruction

The cross-linking data obtained by the track system and the calorimeter is implemented. This is implemented taking into account the geometric intersection of the calorimeter clusters.

The algorithm for the cross-linking data obtained by the track system and the calorimeter:

• union of geometrically intersecting calorimetric clusters
• finding a match between calorimetric clusters and tracks
• recalculating cluster characteristics (time, energy, cluster size, conversion point)

• 

  The reconstruction efficiency for different particle types

Muon system

The muon system works using the results of a reconducted stand-alone simulation on G4BeamLine. The system is a cylinder of eight absorber and sensitive polystyrene layers. The absorber is iron.

• 

  The probability distribution for muons and pions to reach a certain layer in the muon system

Output collection

The output ROOT-file contains:

• allGenParticles - MC particles
  • pdgId
  • charge
  • vertex - x, y, and z coordinates
  • p4 - momentum (px, py, pz) and mass

• Particles - the particle characteristics after the parametric simulation
  • pdgId
  • charge
  • vertex - x, y, z coordinates
  • p4 - measured momentum (px, py, pz) and the most probability particle mass
  • dedx
  • dedx_err
  • dncldx - cluster counting
  • dedxPid
  • dncldxPid
  • farichPid
  • muPid

• TrackState - the helix characteristics (the track)
  • phi
  • theta
  • qOverP
  • d0
  • z0
  • referencePoint - x, y and z coordinates

• CaloClusters
  • energy
  • time
  • position - x, y and z coordinates of the calorimeter entry point

• MuonHits
  • layer - the last layer that registered a particle

• FARICHHits
  • cellId
  • energy
  • time
  • beta
  • beta_err
  • nphe0
  • nphe

The more characteristics have intuitive names.

SctParSim (Python)

How to run

Login to stark or proxima machine.

ssh stark -X
setupSCTAU; asetup SCTauSim,master,latest
mkdir workarea
cd workarea
mkdir run
cd run
cp /home/razuvaev/public/misc/pi_ms_f1_mppc2_px3_d200_mla4_graph2d.root .
cp /home/razuvaev/public/misc/gun1.cfg .
cp /home/razuvaev/public/misc/g4beamline_pi_plus_100k_parse.root .
cp /home/razuvaev/public/misc/g4beamline_mu_plus_100k_parse.root .
cp /home/whitem/public/misc/pi_p.root .
cp /home/whitem/public/misc/pi_m.root .
cp /home/whitem/public/misc/mu_p.root .
cp /home/whitem/public/misc/mu_m.root .
runparsim.py

Options

Option	Run example	Description
-b, --batch	runparsim.py -b	Turn on the batch mode. Suppress EventDisplay execution.
-c, --change	runparsim.py -c my_cfg_file.dat	Change some parameters of the detector.
-n, --neve	runparsim.py -n 31415	The number of events to process.
-g, --gun	runparsim.py -g	Turn on the particle gun mode.
-ig, --input-gun	runparsim.py -g -ig my_gun.dat	Input particle gun configuration file.
-i, --input	runparsim.py -i gen_dkpipi0.root	Specify the input file.
-o, --output	runparsim.py -o parsim_dkpipi0.root	Specify the output file.
--profile	runparsim.py --profile	Turn on the cProfile to analyse the performance.

Event display

The event display has two projections: x-y and y-z. All detector subsystems are presented. Some of them overlay, especially PIDs, it is not important for parametric simulation, but let's study several options at once. All particles from AllGenParticles branch are presented at the plot by lines of different styles, colours and thicknesses. Somehow the line thickness corresponds to the particle mass, the wide line --- the more massive particle. Warm colours are devoted to positive charged particles and cold to negative ones. Also, particle lines are labeled.

The event display is switched on by default. To switch it off run simulation with -b option.

Detector configuration

The detector parameters can be changed via a configuration file my_cfg_file.dat placed in the main simulation folder. The file has a simple structure --- one parameter and its value(s) per line. A parameter's name and value should be separated by spaces. Arrays should be written in [] brackets. The values in arrays should be separated by commas. Empty lines and lines contained incorrectly parameter names are ignored.

In the example below the parameter at the first line and the second line is one number, while the parameter at the third line is an array.

trck.minPt 0.05
trck.corrMtx.pij -0.08
calo.resPar [0.167,0.0,0.011]

The parameters can be given in any order.

All detector parameters can be viewed in the configuration files:

Subsystem	Congiguration file	Name to change parameters
ASHIPH	ashiphpars_std01.json	ashiph1030
Calorimeter	calopars_std01.json	calo
FARICH	farichpars_std01.json	farich
FDIRC	fdircpars_std01.json	fdirc
Muon system	muonpars_std01.json	muon
ToF	tofpars_std01.json	tof
ToP	toppars_std01.json	top
Tracker	trkpars_std01.json	tracker

The detector subsystems sizes are stored in detlayout_std01.json. They can be changed in the same way.

Pictures

• 

  FDIRC angle vs true momentum.

PAPAS (Old)

About papas, heppy et cetra

Particle propagation is done by geometry calculation. To valid the calculation several different cases were plotted.

Helix.

Configure detector parameters

The detector parameters can be changed via a configuration file CTauPapas.cfg placed in the main papas simulation folder. The file has a simple structure --- one parameter and its value(s) per line. A parameter's name and value(s) should be separated by spaces. Empty lines and lines beginning with # are ignored.

In the example below the parameter at the first line is one number, while the parameter at the second line is an array.

ecal_emin_barrel 0.05

ecal_eres 1.34e-2 0.066e-2 0 0.82e-2

The parameters can be given in any order.

Configure detector parameters

The file ctau_input_sim.txt contains two lines. The first line is the path to a primary simulation file (see MC Data Sets page). The second line is an integer number of events to be processed.

How to run papas

Copy a directory with papas on stark the machine and go to this directory.

cd

cp -rf ~razuvaev/myheppy .

cd myheppy

There are a directory output for output files, detector configuration file CTauPapas.cfg, file ctau_input_sim.txt with a path to the file with primary generator events, and the folder heppy with heppy code itself. Let's go into it and tune environment.

cd heppy

source init.sh

Now it is time to run papas. You may be asked a question because the output directory is not empty. So just input y or clean the folder.

cd test

./heppy_loop.py ../../output/ ctau_cfg1.py

If it don't want to run try source ~razuvaev/.bashrc and source ../init.sh because it can be caused by the problem with environment variables.

When papas simulation has been done one need to present papas output to a suitable form and also add initial generator information.

cd ../../

./txt2tree.py

The output root tree is available in the file myheppy/output/txt2tree.root.

Output tree

The output tree contains branches which can be divided in several groups:

• reconstructed particle parameters;
• generated particle parameters;
• generated vertices;
• connection between reconstructed particles, generated particles and generated vertices.

The table below presents branches and description of their content.

Name	Type	Length	Description
Reconstructed particles
n	int	1	The number of reconstructed particles.
px	float []	n	The reconstructed particle momentum: x coordinate.
py	float []	n	The reconstructed particle momentum: y coordinate.
pz	float []	n	The reconstructed particle momentum: z coordinate.
Generated particles
n0	int	1	The number of generated particles.
px0	float []	n0	The generated particle momentum: x coordinate.
py0	float []	n0	The generated particle momentum: y coordinate.
pz0	float []	n0	The generated particle momentum: z coordinate.
Generated vertices
nv0	int	1	The number of generated vertices.
vx0	float []	nv0	The generated vertex: x coordinate.
vy0	float []	nv0	The generated vertex: y coordinate.
vz0	float []	nv0	The generated vertex: z coordinate.
Links
recgen	int []	n	Transform a reconstructed particle index to the generated particle index.
genver	int []	n0	Transform a generated particle index to the generated vertex index.

Analysis example

Here a short analysis example of $D^0 \to K_S^0 \pi^+ \pi^-$ is presented. The things are performed with PyROOT.

The data a taken from the available exclusive sample.

The code can be taken from github [1] or find at the stark cluster: /home/razuvaev/myheppy/search_dkspipi.py.

• 

  $K_S^0$ mass vs $D^0$ mass.

• 

  $D^0$ mass vs its momentum.