<<O>>  Difference Topic AlgoritmoParticleFlow (r1.4 - 23 Dec 2008 - Main.iglesias)

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4. Algoritmo Particle Flow en la zona hacia delante

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4.a.i. Introduccion

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El algoritmo Particle Flow empezo a desarrollarse en la era LEP, y tambien ha sido utilizado en Tevatron y en el LHC, tanto en CMS como en ATLAS (ver mi web de ATLAS: http://ific.uv.es/~iglesias), y para el futuro acelerador lineal ILC, los detectores ILD y SiD? adoptaran un diseño basado en el Particle Flow, porque este concepto promete alcanzar la resolucion en energia de los jets que se quiere conseguir.
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El algoritmo Particle Flow empezo a desarrollarse en la era LEP, y tambien ha sido utilizado en Tevatron y en el LHC, tanto en CMS como en ATLAS (ver mi web de ATLAS: http://ific.uv.es/~iglesias), y para el futuro acelerador lineal ILC, los detectores ILD y SiD adoptaran un diseño basado en el Particle Flow, porque este concepto promete alcanzar la resolucion en energia de los jets que se quiere conseguir.

Pero para este fin, Particle Flow requerie que se desarrolle una nueva tecnologia de detectores ademas de unos nuevos algoritmos de reconstruccion mas sofisticados.

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4.a.ii.Concepto de Particle Flow

As you know, in a typical jet, we have:
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  • 64% of jet energy in charged hadrons (mainly pion ±)
  • 25 % in photons (mainly from 0 decays)
  • 11 % in neutral hadrons (: mainly KL and neutrons)
About 2/3 of the jet energy are carried by charged particles (p,K...). However jet algorithm makes no use of tracking information
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  • 64% of jet energy in charged hadrons (mainly π±)
  • 25 % in photons (mainly from π→γγ decays)
  • 11 % in neutral hadrons (mainly KL and neutrons)
About 2/3 of the jet energy are carried by charged particles (protons, kaons...). However jet algorithm makes no use of tracking information

Particle Flow algorithm make an optimal use of the detector information combining the measurement of the energy deposition in calorimeter cells with the reconstructed track in the inner detector to improve jet energy resolution and ETMiss.

For ILC energies, the tracker is more precise than the calorimeters. As you can see in this picture, tracking is better than:

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  • ECAL for Epart < 120 GeV?
  • EHAD for Epart < 370 GeV?
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  • ECAL for Epart < 120 GeV
  • EHAD for Epart < 370 GeV

So for charged particles, their energy resolution will be sustituted by the track momentum resolution in order to have a better resolution in jet ET.
Energy_resolution_ILC.jpg
 <<O>>  Difference Topic AlgoritmoParticleFlow (r1.3 - 22 Dec 2008 - Main.iglesias)

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4. Algoritmo Particle Flow en la zona hacia delante

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Traditional calorimetric approach:

  • Measure all components of jet energy in ECAL/HCAL !
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  • ~70 % of energy measured in HCAL:
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  • ~70 % of energy measured in HCAL: HCAL_energy_resolution.jpg

  • Intrinsically “poor”HCAL resolution limits jet energy resolution


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The idea is, for a detector ideal in separating the different particles:

  • The charged tracks will be measured from the tracker
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  • The photons from the Ecal:
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  • The photons from the Ecal: ECAL_energy_resolution.jpg

  • And only the neutral hadrons will be measured in the Hcal (and possibly in Ecal)
So, only 10 % of jet energy from HCAL  much improved resolution
Line: 76 to 76

4.a.v. La calorimetria con Particle Flow

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In practice, particle flow performance depends on the ability to associated energy deposits without double counting or merging energy deposits. This places stringent requirements on the granularity of ECAL and HCAL and, consequently, Particle Flow performance is one of the main factors driving the overall detector design.

The jet energy resolution obtained is the combination of the detector and PFA software performance.


4.a.vi.Como funciona el Particle Flow?

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The crucial step of the particle flow algorithm is the correct assignment of calorimeter hits to the charged particles and the efficient discrimination of close-by showers produced by charged and neutral particles.

The main steps in the Particle Flow algorithm are:

  • Track Reconstruction
  • Extrapolate track to calorimeters
  • Assign MIP to stubs to tracks
  • Clustering in calorimeters
  • Particle ID for Charged particle
  • Removed charged particle hits in calorimeter
  • Clustering of neutral hits
  • Particle ID for neutral


howPFworks.jpg


-- Main.iglesias - 22 Dec 2008

Line: 88 to 111

META FILEATTACHMENT Energy_resolution_ILC.jpg attr="" comment="" date="1229949384" path="C:\Users\iglesias\Documents\My_Work_USC\My_Work\ILC_my_work\Presentaciones\Plot_Particle_Flow_SiLC_Meeting\Energy_resolution_ILC.jpg" size="12315" user="iglesias" version="1.1"
META FILEATTACHMENT Particle_Flow_Paradigm.jpg attr="" comment="" date="1229949568" path="C:\Users\iglesias\Documents\My_Work_USC\My_Work\ILC_my_work\Presentaciones\Plot_Particle_Flow_SiLC_Meeting\Particle_Flow_Paradigm.jpg" size="31561" user="iglesias" version="1.1"
META FILEATTACHMENT Part_Flow_Reconstruction.jpg attr="" comment="" date="1229949960" path="C:\Users\iglesias\Documents\My_Work_USC\My_Work\ILC_my_work\Presentaciones\Plot_Particle_Flow_SiLC_Meeting\Part_Flow_Reconstruction.jpg" size="29842" user="iglesias" version="1.1"
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META FILEATTACHMENT howPFworks.jpg attr="" comment="" date="1229957853" path="C:\Users\iglesias\Documents\My_Work_USC\My_Work\ILC_my_work\Presentaciones\Plot_Particle_Flow_SiLC_Meeting\how PF works.jpg" size="21605" user="iglesias" version="1.1"
META FILEATTACHMENT HCAL_energy_resolution.jpg attr="" comment="" date="1229958494" path="C:\Users\iglesias\Documents\My_Work_USC\My_Work\ILC_my_work\Presentaciones\Plot_Particle_Flow_SiLC_Meeting\HCAL_energy_resolution.jpg" size="3272" user="iglesias" version="1.1"
META FILEATTACHMENT ECAL_energy_resolution.jpg attr="" comment="" date="1229958504" path="C:\Users\iglesias\Documents\My_Work_USC\My_Work\ILC_my_work\Presentaciones\Plot_Particle_Flow_SiLC_Meeting\ECAL_energy_resolution.jpg" size="3328" user="iglesias" version="1.1"
 <<O>>  Difference Topic AlgoritmoParticleFlow (r1.2 - 22 Dec 2008 - Main.iglesias)

META TOPICPARENT WebHome
Changed:
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>
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4. Algoritmo Particle Flow en la zona hacia delante

4.a. Algoritmo Particle Flow

4.a.i. Introduccion


El algoritmo Particle Flow empezo a desarrollarse en la era LEP, y tambien ha sido utilizado en Tevatron y en el LHC, tanto en CMS como en ATLAS (ver mi web de ATLAS: http://ific.uv.es/~iglesias), y para el futuro acelerador lineal ILC, los detectores ILD y SiD? adoptaran un diseño basado en el Particle Flow, porque este concepto promete alcanzar la resolucion en energia de los jets que se quiere conseguir.

Pero para este fin, Particle Flow requerie que se desarrolle una nueva tecnologia de detectores ademas de unos nuevos algoritmos de reconstruccion mas sofisticados.

Line: 11 to 15

  • requisitos de la calorimetria: alta granularidad y cobertura a todo angulo
  • requisitos del detector de trazas: buena resolucion el momento de las trazas, incluso a muy bajos angulos.
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      • Concepto de Particle Flow
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4.a.ii.Concepto de Particle Flow

As you know, in a typical jet, we have:
  • 64% of jet energy in charged hadrons (mainly pion ±)
  • 25 % in photons (mainly from 0 decays)
  • 11 % in neutral hadrons (: mainly KL and neutrons)
About 2/3 of the jet energy are carried by charged particles (p,K...). However jet algorithm makes no use of tracking information

Particle Flow algorithm make an optimal use of the detector information combining the measurement of the energy deposition in calorimeter cells with the reconstructed track in the inner detector to improve jet energy resolution and ETMiss.

For ILC energies, the tracker is more precise than the calorimeters. As you can see in this picture, tracking is better than:

  • ECAL for Epart < 120 GeV?
  • EHAD for Epart < 370 GeV?
So for charged particles, their energy resolution will be sustituted by the track momentum resolution in order to have a better resolution in jet ET.
Energy_resolution_ILC.jpg

4.a.iii. Metodo de calorimetria tradiccional vs Paradigma de Particle Flow

Traditional calorimetric approach:

  • Measure all components of jet energy in ECAL/HCAL !
  • ~70 % of energy measured in HCAL:
  • Intrinsically “poor”HCAL resolution limits jet energy resolution


Particle_Flow_Paradigm.jpg


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      • Metodo de calorimetria tradiccional vs Paradigma de Particle Flow

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      • Reconstruccion con Particle Flow
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Particle Flow Paradigm:

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      • La calorimetria con Particle Flow
>
>
The idea is, for a detector ideal in separating the different particles:
  • The charged tracks will be measured from the tracker
  • The photons from the Ecal:
  • And only the neutral hadrons will be measured in the Hcal (and possibly in Ecal)
So, only 10 % of jet energy from HCAL  much improved resolution

4.a.iv. Reconstruccion con Particle Flow

But for a real detector two effects play a role:

  • 1- Particles travelling at small angles to the beam axis will not be detected.
  • 2- It is not possible to perfectly associate all energy deposits with the correct particles:
    • a- The existence of an effective threshold on
      • Charged particles due to the high magnetic field needed for background, precision and separation
      • photons due to cell threshold and physical background
    • b- The probability of confusion:
      • efficiency of track reconstruction
      • vertex misidentification
      • wrong associations between tracks and calorimeter cells

In this way, for the recontruction of a particle flow calorimeter we must to avoid double counting of energy from same particles, as well as we have to separate energy deposits from different particles, because, as you can see in the picture…
Part_Flow_Reconstruction.jpg

So, the energy resolution of the jet will be determinates by the level of mistakes and confusion not only by the intrinsic calorimeter performance of ECAL and hadronic calorimeter.

4.a.v. La calorimetria con Particle Flow

4.a.vi.Como funciona el Particle Flow?


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      • Como funciona el Particle Flow?

-- Main.iglesias - 22 Dec 2008
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META FILEATTACHMENT Area_analisis_forward_ILD.jpg attr="" comment="" date="1229948850" path="C:\Users\iglesias\Documents\My_Work_USC\My_Work\ILC_my_work\Presentaciones\Plot_Particle_Flow_SiLC_Meeting\Area_analisis_forward_ILD.jpg" size="64244" user="iglesias" version="1.1"
META FILEATTACHMENT Energy_resolution_ILC.jpg attr="" comment="" date="1229949384" path="C:\Users\iglesias\Documents\My_Work_USC\My_Work\ILC_my_work\Presentaciones\Plot_Particle_Flow_SiLC_Meeting\Energy_resolution_ILC.jpg" size="12315" user="iglesias" version="1.1"
META FILEATTACHMENT Particle_Flow_Paradigm.jpg attr="" comment="" date="1229949568" path="C:\Users\iglesias\Documents\My_Work_USC\My_Work\ILC_my_work\Presentaciones\Plot_Particle_Flow_SiLC_Meeting\Particle_Flow_Paradigm.jpg" size="31561" user="iglesias" version="1.1"
META FILEATTACHMENT Part_Flow_Reconstruction.jpg attr="" comment="" date="1229949960" path="C:\Users\iglesias\Documents\My_Work_USC\My_Work\ILC_my_work\Presentaciones\Plot_Particle_Flow_SiLC_Meeting\Part_Flow_Reconstruction.jpg" size="29842" user="iglesias" version="1.1"
 <<O>>  Difference Topic AlgoritmoParticleFlow (r1.1 - 22 Dec 2008 - Main.iglesias)
Line: 1 to 1
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META TOPICPARENT WebHome
El algoritmo Particle Flow empezo a desarrollarse en la era LEP, y tambien ha sido utilizado en Tevatron y en el LHC, tanto en CMS como en ATLAS (ver mi web de ATLAS: http://ific.uv.es/~iglesias), y para el futuro acelerador lineal ILC, los detectores ILD y SiD? adoptaran un diseño basado en el Particle Flow, porque este concepto promete alcanzar la resolucion en energia de los jets que se quiere conseguir.

Pero para este fin, Particle Flow requerie que se desarrolle una nueva tecnologia de detectores ademas de unos nuevos algoritmos de reconstruccion mas sofisticados.

Paricle Flow tiene ademas unas altas exigencias tanto a nivel de calorimetria como del detector de trazas:

  • requisitos de la calorimetria: alta granularidad y cobertura a todo angulo
  • requisitos del detector de trazas: buena resolucion el momento de las trazas, incluso a muy bajos angulos.

      • Concepto de Particle Flow

      • Metodo de calorimetria tradiccional vs Paradigma de Particle Flow

      • Reconstruccion con Particle Flow

      • La calorimetria con Particle Flow

      • Como funciona el Particle Flow?
-- Main.iglesias - 22 Dec 2008
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Revision r1.1 - 22 Dec 2008 - 09:30 - Main.iglesias
Revision r1.4 - 23 Dec 2008 - 11:50 - Main.iglesias