Particle identification in ECAL

1. Particle identification in ECAL Alexander Artamonov, Yuri Kharlov IHEP, Protvino CBM collaboration meeting 14-17.10.2008

2. PID in ECAL 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

3. PID in ECAL 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

4. PID in ECAL Simulation model • 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

5. PID in ECAL 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

6. PID in ECAL Energy resolution ECAL energy resolution as a function of photon energy.

7. PID in ECAL Neutron contamination to photon spectrum: 1D case The energy deposition in the whole module caused by 2 GeV photon and 1,2,3,4 GeV/c neutron

8. PID in ECAL Neutron contamination to photon spectrum 2D case 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)

9. PID in ECAL Neutron contamination to photon spectrum 2D case 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)

10. PID in ECAL Neutron contamination to photon spectrum 2D case 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)

11. PID in ECAL Neutron contamination to photon spectrum 2D case 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)

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

13. PID in ECAL 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

14. PID in ECAL 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

15. PID in ECAL 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

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

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

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

19. PID in ECAL 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

20. PID in ECAL Momentum distribution for various particle species from UrQMD

21. PID in ECAL Definition of convolution integral

22. PID in ECAL Integral contamination of photon spectrum by neutrons 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)

23. PID in ECAL 1-segmented modules vs 2-segmented one Ratio of probabilities for neutron with any momentum to fake photon with a given energy

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

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

26. PID in ECAL Probabilities and their ratios for K0L and proton with any momentum to fake photon with a given energy

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

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

29. PID in ECAL Conclusion • 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 • 9.110-4 of neutrons, • 1.7 10-4 of K0L, • 3.5 10-6 of antineutrons, • 1.5 10-4 of Lambda(1115), • 1.210-3 of -, • 9.8 10-4 of +, • 8.810-4 of protons • PID has been studied for 19 combinations of segment thickness. The most optimum segment combinations are 14X0+6X0 and 15X0+5X0.