Particle identification in ECAL

Alexander Artamonov, Yuri KharlovIHEP, Protvino

CBM collaboration meeting 14-17.10.2008

PID in CBM In CBM, the particle identification (PID) is realized in TOF, TRD,

RICH and ECAL

The main object of ECAL PID is to discriminate photons and e+- from other particles

The ECAL PID is based mainly on an investigation of transverse shower shape analysis

A subject of this study is to perform the ECAL PID by using just longitudinal shower shape analysis

The most simple case has been studied when ECAL module consists of 2 longitudinal segments

This case is very close to the current design of ECAL, since it consists of preshower and ECAL modules

Method used is to analyse 2D plot, namely an energy deposition in the 1st segment of ECAL module versus an energy deposition in the whole ECAL module

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PID in ECAL

Photon can be identified in ECAL by several methods:

Track matching with ECAL cluster Time of flight measured by ECAL Lateral shower shape Longitudinal shower profile

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Framework – cbmroot as a new detector module segcal 1 ECAL module with 160 layers (Pb 0.7 mm + Sci 1.0 mm) 20 longitudinal segments, each one consists of 8 layers Effective radiation length of the ECAL module: 1.335 cm Total radiation length of the ECAL module: 20.4 X0 A single primary particle (photon, muon, pion, kaon, proton,

neutron, antineutron and Lambda(1115)) with energies 1, 2, 3, ..., 23, 24, 25 GeV

Simulation model

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Various combinations of segment thickness:

1 X0 (in 1st segment) + 19 X0 (in 2nd segment) 2 X0 (in 1st segment) + 18 X0 (in 2nd segment) 3 X0 (in 1st segment) + 17 X0 (in 2nd segment) 4 X0 (in 1st segment) + 16 X0 (in 2nd segment) 5 X0 (in 1st segment) + 15 X0 (in 2nd segment) 6 X0 (in 1st segment) + 14 X0 (in 2nd segment) 7 X0 (in 1st segment) + 13 X0 (in 2nd segment) 8 X0 (in 1st segment) + 12 X0 (in 2nd segment) 9 X0 (in 1st segment) + 11 X0 (in 2nd segment) 10 X0 (in 1st segment) + 10 X0 (in 2nd segment)

11 X0 (in 1st segment) + 9 X0 (in 2nd segment) 12 X0 (in 1st segment) + 8 X0 (in 2nd segment) 13 X0 (in 1st segment) + 7 X0 (in 2nd segment) 14 X0 (in 1st segment) + 6 X0 (in 2nd segment) 15 X0 (in 1st segment) + 5 X0 (in 2nd segment) 16 X0 (in 1st segment) + 4 X0 (in 2nd segment) 17 X0 (in 1st segment) + 3 X0 (in 2nd segment) 18 X0 (in 1st segment) + 2 X0 (in 2nd segment) 19 X0 (in 1st segment) + 1 X0 (in 2nd segment)

Particle identification is based on relation between the total energy and the energy in the first segment:

E1 vs Etot

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ECAL energy resolution as a function of photon energy.

Energy resolution

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The energy deposition in the whole module caused by 2 GeV photon and 1,2,3,4 GeV/c neutron

Neutron contamination to photon spectrum: 1D case

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The energy deposition in the 1st segment versus the full energy deposition. Black points correspond to 2 GeV photons, red points correspond to 1 GeV/c neutrons. Segmentation: 10 X0 (1st segment) + 10 X0 (2nd segment)

Neutron contamination to photon spectrum 2D case

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The energy deposition in the 1st segment versus the energy deposition in the whole module. The same plot but with one additional population originated from 2 GeV/c neutrons (blue points)

Neutron contamination to photon spectrum 2D case

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The energy deposition in the 1st segment versus the energy deposition in the whole module. The same plot but with one additional population originated from 3 GeV/c neutrons (green points)

Neutron contamination to photon spectrum 2D case

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The energy deposition in the 1st segment versus the energy deposition in the whole module. The same plot but with one additional population originated from 4 GeV/c neutrons (magenta points)

Neutron contamination to photon spectrum 2D case

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Probabilities for neutron to fake 2 GeV photon. This plot corresponds to the following segment structure: 10X0+10X0

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Probabilities for neutron to fake 2 GeV photon (red curve), 3 GeV photon (green curve) and 4 GeV photon (blue curve). Segment structure: 10X0+10X0

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Probabilities for neutron to fake 2 GeV photon (red curve), 3 GeV photon (green curve), 4 GeV photon (blue curve), 5 GeV photon (yellow curve), 6 GeV photon (magenta curve), 7 GeV photon (cyan curve) and 8 GeV photon (deep green curve). Segment structure: 10X0+10X0

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Probabilities for neutron to fake 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ..., 23, 24 and 25 GeV photons. Segment structure: 10X0+10X0

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Probabilities for neutron to fake 2 GeV photon in module with 2 segments 10X0+10X0 (red curve) and the whole module (black curve)

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Probabilities for neutron to fake 4 GeV photon in module with 2 segments 10X0+10X0 (red curve) and the whole module (black curve)

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Probabilities for neutron to fake 10 GeV photon in module with 2 segments 10X0+10X0 (red curve) and the whole module (black curve)

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Expected behaviour of probability for neutron with momentum P [GeV/c] to fake, for example, 2 GeV photon (where P > 2 GeV)

To obtain a probability for neutron with ANY momentum to fake the 2 GeV photon, one needs to use the following convolution integral:

Expected behaviour of the probability for neutron with ANY momentum to fake the 2 GeV photon

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Momentum distribution for various particle species from UrQMD

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Definition of convolution integral

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Probabilities for neutron with any momentum to fake photon with a given energy in module with 2 segments 10X0+10X0 (red curve) and the whole module (black curve)

Integral contamination of photon spectrum by neutrons

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Ratio of probabilities for neutron with any momentum to fake photon with a given energy

1-segmented modules vs 2-segmented one

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Probabilities and their ratios for neutron with any momentum to fake photon with a given energy for various segment thickness14.10.2008 24PID in ECAL

Probabilities and their ratios for neutron with any momentum to fake photon with a given energy for various segment thickness14.10.2008 25PID in ECAL

Probabilities and their ratios for K0L and proton with any momentum to fake

photon with a given energy14.10.2008 26PID in ECAL

Probabilities and their ratios for (1115) and antineutron with any momentum to fake photon with a given energy14.10.2008 27PID in ECAL

Probabilities and their ratios for + and - with any momentum to fake photon with a given energy14.10.2008 28PID in ECAL

The 1st practical realization of the well known procedure for performing the ECAL PID in the 1D case (whole ECAL module) and the 2D case (ECAL module with 2 segments) were done

The probabilities for hadrons and muons of various momenta P to fake a photon of various energies E were obtained. For example, in the segment structure 14X0+6X0, 5 GeV photon can be faked by 5.3e-03 of 6 GeV/c neutrons, by 2.9e-02 of 6 GeV/c K0L, by 4.8e-02 of 6 GeV/c antineutrons, by 5.1e-03 of 6 GeV/c Lambda(1115), by 4.7e-02 of 6 GeV/c pi-, by 3.4e-02 of 6 GeV/c pi+, by 5.4e-03 of 6 GeV/c protons, by 6.0e-05 of 7 GeV/c muons

The probabilities for hadrons of ANY momenta P (integrated over momenta of the hadrons) to fake a photon of various energies E were obtained. For example, in the segment structure 14X0+6X0, 5 GeV photon can be faked by

9.110-4 of neutrons, 1.7 10-4 of K0

L, 3.5 10-6 of antineutrons, 1.5 10-4 of Lambda(1115), 1.210-3 of -, 9.8 10-4 of +, 8.810-4 of protons

PID has been studied for 19 combinations of segment thickness. The most optimum segment combinations are 14X0+6X0 and 15X0+5X0.

Conclusion

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