physics validation meeting w. pokorski / cern

16/04/2003 Simulation Application for the LHCb Experiment

Physics validation meeting

W. Pokorski / CERN

Simulation Application for the LHCb Experiment


Physics validation

comparison to the test-beam datavalidation of Rayleigh scattering, Cherenkov radiation, photoelectric effect, energy loss in the Silicon for RICH detectors

studies of different hadronic physics models in hadronic calorimeter simulations

comparison to the Geant 3 simulationoccupancies, momentum distributions, time of flight, energy deposition distributions, etc

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• To identify charged particles in the momentum range 1-150 GeV/c.• Two detectors: RICH1, RICH2.

RICH1: Aerogel 210 GeV/c C4F10 < 70 GeV/c RICH2: CF4 <150 GeV/c.

• Photo Detectors: Baseline solution- HybridPhotodiodes (HPD).

• RICH test beam presented: To test the performance of the Aerogel radiator.

Momentum range

S. Easo

RICH detectors in LHCb


TestTest beam Set-up at CERNTestTest beam Set-up at CERN

Beam from CERN-PS: πˉ and p/π in the range 6 – 10 GeV/c (Δp/p = 1%)

S. Easo


Simulation of the Testbeam Setup.

Mirror Rad. of Curvature=1185 mm.Four Pad Hpds are used.

Mirror

Hpd

Aerogel

Filter

Vessel

S. Easo


Red lines: Charged particleGreen lines : Photons.

Transmission in Aerogel, Cherenkov radiation, Rayleigh scattering, etc, simulated properly

S. Easo

A Typical event in the Testbeam


Thickness No filter Filter D263

θc σθ θc σθ

4 cm 250.0 5.4248.7 4.0

247.1 5.0246.8 3.1

8 cm 246.8 5.8245.0 3.9

245.4 4.8243.7 3.0

DataMC

Aerogel fromNovosibirsk

• Results per single photoelectronsingle photoelectron in (mrad):

DataMC

Cherenkov Angle reconstruction

Components of σθ

in mrad for the case with filter.

Pixel size : 1.3Chromatic: 2.5Emission Pt: 1.1

Beam divergence: 0.7

Misalignment: ~ 2.2 (not included in σθ MC )

MC resolutionWithoutMisalignment


•Standard Geant4 processes not applicable in this case (tabularized quantum efficiency data available from the manufacturer)

•A Special class created to generate the photoelectrons, which is derived from a GEANT4 base class.

•This process uses the quantum efficiency data and the results of Fountain focussing tests. Electron Energy: High Voltage applied.

Direction: From Fountain focussing.

• The quantum efficiency data includes the loss of photons by reflection at the Hpd quartz window surface.

S. Easo

Photoelectric Effect at the HPD


• Implemented using a special process class since the standard Geant4 procedure too complex for this purpose

• the only important point: photoelectrons loose all their energy in the Si

• The backscattering causes a loss of efficiency in creating hits Parameterized efficiency = 1.0 - B* N/S

where N = threshold cut in terms of width of the pedestal = 4 S= Signal to noise ratio=10 B= backscattering probability=0.18.

S. Easo

Hit Creation in the Si Detector


RICH1 with SingleParticleGun

Pion with 7 GeV/c. Cherenkov PhotonsIn Aerogel and C4F10.

RICH1 Event

Rayleigh scatteringSwitched off forIllustration.

S. Easo


RICH Simulation Plans.

• At least one test beam expected in October 2003 with gas radiators and new versions of the Photodetectors.

• Another testbeam with new versions of Aerogel also possible in October.

• All these will be simulated using GEANT4.

• In addition, we are expecting the LHCb-RICH simulation within the GAUSS framework to be in production by the end of 2003.

S.Easo, RAL,14-04-2003


• HCAL is a sampling device made out of steel as absorber and scintillating tiles are active material.

• The scintillating tiles run parallel to the beam axis.

• It will provide data for the LHCb hadron trigger.

• Testbeam studies of the response to particles incident at various angles is studied

• comparison to simulation I. Belyaev +A. Berdiouguine et al.

HCAL Test beam


Response to 50 GeV/c Pions

• Testbeam (1) Data , GEANT3 (MICAP +FLUKA).• HCAL TDR.

•Testbeam (2) Data, GEANT4.

Histogram : Real DataDots: Simulation

I. Belyaev +A. Berdiouguine et al.

Energy Response in HCAL


Energy Resolution of HCAL

• Testbeam Data, GEANT3• GEANT3 with GEISHA, FLUKA,MICAP

• Testbeam Data , GEANT4• G4+GEISHA agrees with G3+GEISHA.• Need help to understand and use G4 with QGS+CHIPS

• Data G4 (QGS+CHIPS) G4(GEISHA)

Data and G3

Data and G4

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I. Belyaev +A. Berdiouguine et al.


Calorimeters test-beam

ALL LHCb calorimeters Spd/Prs/Ecal/HCal will have test beam periods this summer between the middle of June and end of August

very detailed and realistic Xml description of all our complex modules calorimeters in Gauss (the LHCb simulation application) - no plans to perform a stand alone G4 simulation for our calorimeters

if needed, addition (simplified) geometry will be implemented to be used within Gauss

full simulation of test beam setups will be performed with Geant4 (Gauss) and the data will compared

I. Belyaev


Vertex Locator physics validation (1/2)

Geant3Geant4

Number of hits per event Energy deposition in the silicon (eV)

Geant3

Geant4

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Vertex Locator physics validation (2/2)

Geant3

Geant4

Geant3

Geant4

Time of Flight (ns) Particle energy (GeV)

13


Outer Tracker physics validation (1/2)

Geant3Geant4

XY distributionNumber of hits per event

14


Outer Tracker physics validation (2/2)

Time Of Flight (ns)Momentum distribution (GeV)

Geant3Geant4

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16/04/2003 Simulation Application for the LHCb Experiment 16

Summary

LHCb puts no further effort on developing G3 based application, all of it has been moved to G4 based one

we can run GEANT4 simulation with all the subdetectors included (complete LHCb detector geometry), realistic Pythia events and Geant4 proposed physics list

we are testing/validating subdetector specific code and physics processes

we are planning large test productions starting from the summer

definite move from the old Geant3 simulation to the new Geant4 based one, early next year

conclusion: we are serious about Geant4 and we are very interested in the physics validation

physics validation meeting w. pokorski / cern

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