Muon simulations

1. Muon simulations Anna Kiseleva

2. Outline • Muon system 2006 • New Muon Chamber system (MuCh) • Track finding und selection • Results for low-mass vector mesons • J/ψ simulations • Detector resolution study: preliminary results • Conclusions and next steps

3. MuCh system 2006 • Outside of the magnet • Detector in front of the system • First thin absorber • Thick last absorber • 10 cm gap • Distance – 5.5 m 51020 30 120 cm W Fe C 551cm 0 cm 150 cm 10 cm

4. Problems STS for MuCh MuCh at 25 AGeV 1 2 MAPS? 0 123 4 5 6 Track reconstruction 3 ωat 25 AGeV: S/B = 8×10-2 efficiency = 4.4% too many μ from weak decays! ● 50 KeV E-cutoff

5. Problems Track reconstruction 3 ωat 25 AGeV: S/B = 8×10-2 efficiency = 4.4% too many μ from weak decays! μ π

6. Modifications STS for MuCh Increasing of the pipe hole 1 2 no MAPS! 5.7˚(0.1 rad) 3.0˚ 0 1 23 4 5 6 ωat 15 AGeV: MAPS no MAPS S/B 8×10-2 7×10-2 efficiency 2.4% 2.2% More compact MuCh! ωat 25 AGeV: old new S/B 8×10-2 8×10-2 efficiency 4.4% 3.6% 3

7. MuCh detector 2007 • Fist absorber inside of the magnet • Last STS as a first detector • First thick absorber • 5 cm gap • Distance – 2.6 m (instead of 5.5 m) 20 20 20 30 35 cm 260cm Fe Fe Fe Fe Fe 5 cm 0 cm 102.5 cm

8. Max rate of particles 0 1 2 3 4 5 Energy of beam ● 15 AGeV ● 25 AGeV ● 35 AGeV

9. STS Hybrid (750 μm) 30 cm 40 cm Strip (400 μm) 50 cm 60 cm 75 cm 100 cm

10. CBM setup STS MuCh TRD ToF

11. Simulations • Signals (Pluto): • ρ, ω, φ, η and ηDalitz • J/ψ • Background (UrQMD): • central Au+Au at 15, 25 and 35 AGeV • Statistics: • 25 AGeV – 20k events • 15 and 35 AGeV – 10k events

12. Hit producers • STS: • stsDigiVersion = "v05a" • 2 hybrid + 4 strip detectors • MuCh: • 100 μm space resolution • 80 πsec time resolution • ToF: • 0.2 cm space resolution • 80 πsec time resolution

13. Tracking • STS track reconstruction: • ≥ 4 STS hits • χ2primary vertex cut • MuCh track finder: • track selection – hard and soft • χ2track • ToF hit finder: • χ2hit position

14. CBM STS MuCh TRD ToF

15. Tacking into account ToF information PMuCh – Kalman Filter track extrapolation MuCh ToF L PToF = mμ × β × γ β = , t = TToF – TMuCh γ = L c × t 1 √1 – β2

16. PToF vs. Plast MuCh φ signal background

17. PToF vs. Plast MuCh: cuts 1 – branch cut φ signal background 2 – cone cut

18. 25 AGeV Results without cuts Branch cut Cone cut ————— S/B ratio ——————————————————————— ω φ η ηDalitz ρ ω φ η ηDalitz ρ = 0.2 = 0.05 = 0.004 = 0.05 = 0.003 = 2.6 = 5.2 = 1.2 = 0.3 = 2.2 = 0.4 = 0.2 = 0.008 = 0.1 = 0.005 = 1.3 = 2.6 = 0.6 = 0.2 = 1.0 = 0.5 = 0.2 = 0.01 = 0.2 = 0.007 = 1.1 = 2.2 = 0.5 = 0.2 = 0.7 [0.2; 0.3] GeV/c2 [0.2; 0.9] GeV/c2 ————— Efficiency (%) —————————————————————

19. 25 AGeV Invariant mass spectrum signals: ρ ω φ η ηDalitz — background — background+signals branch time cut

20. 25 AGeV Invariant mass spectrum signals: ρ ω φ η ηDalitz — background — background+signals branch time cut

21. 25 AGeV Rapidity of reco ρ0 need more statistics!

22. Types of tracks μ hard μ soft

23. 25 AGeV L β = c × t Cuts for the soft tracks reconstructed on STS momentum β parameter from time measurements mean ± 2σ mean ± 2σ —ρ signal — background — gauss fit —ω signal — background — gauss fit

24. 25 AGeV Results (h-s pairs) hard μ: with branch time cut soft μ: with momentum cut without time with time information information without cuts ————— S/B ratio ——————————————————————— ω φ η ηDalitz ρ ω φ η ηDalitz ρ = 0.02 = 0.006 = 0.0007 = 0.009 = 0.0003 = 2.2 = 3.0 = 1.4 = 0.4 = 1.6 = 0.09 = 0.04 = 0.002 = 0.02 = 0.0008 = 1.4 = 1.8 = 0.9 = 0.3 = 0.9 = 0.15 = 0.06 = 0.003 = 0.02 = 0.001 = 1.2 = 1.6 = 0.8 = 0.2 = 0.8 [0.2; 0.3] GeV/c2 [0.2; 0.9] GeV/c2 ————— Efficiency (%) —————————————————————

25. 25 AGeV Rapidity of reco ρ0 — hard-hard (h-h) pairs — hard-soft (h-s) pairs —h-h + h-s 2 times more statistics!

26. 25 AGeV Efficiency of ρ0RECO (h-h+h-s)  ▼  ▲ ▲   full ptρ(GeV/c): < 0.2 [0.2, 0.4] [0.4, 0.6] [0.6, 0.8] [0.8, 1.0] > 1.0

27. 15 AGeV 25 AGeV 35 AGeV h-s h-h h-s h-h h-s h-h ————— S/B ratio ————————————————————————— ω φ η ηDalitz ρ ω φ η ηDalitz ρ 0.19 0.4 0.03 0.07 0.004 0.008 0.04 0.05 0.002 0.003 1.0 1.0 1.0 1.4 0.7 0.4 0.3 0.06 0.8 0.4 0.15 0.4 0.06 0.2 0.003 0.008 0.02 0.1 0.001 0.005 1.2 1.3 1.6 2.6 0.8 0.6 0.2 0.2 0.8 1.0 0.14 0.4 0.05 0.1 0.002 0.006 0.03 0.04 0.001 0.003 1.3 1.5 1.7 2.7 0.7 0.6 0.4 0.1 0.9 0.8 [0.2; 0.3] GeV/c2 [0.2; 0.9] GeV/c2 ————— Efficiency (%) ——————————————————————— Results hard μ: with branch time cut soft μ: with momentum and time cut

28. Invariant mass spectra hard-hard pairs: background + signals  35 AGeV  25 AGeV  15 AGeV — background

29. 20 20 20 30 35 100 cm Fe Fe Fe Fe Fe Fe J/ψ simulations: add 1m Fe central Au+Au collisions at 25 AGeV meangauss± 2σ • STS track reconstruction: • ≥ 4 STS hits • χ2primary vertex cut • MuCh track finder: • track selection – hard tracks • χ2track no cut on pt and opening angle!

30. J/ψ simulations: cuts without cuts —pt > 1 GeV/c —pt > 1 GeV/c + αopening> 12˚ central Au+Au collisions at 25 AGeV

31. Acceptance of reco J/ψ 4π without cuts % pt > 1 GeV/c %

32. MuCh position resolution position resolution: —— 100μm —— 300μm —— 600μm ——900μm tracking: errorstrack extrapolation~ resolutiondetector

33. Next steps Conclusions on muon detection in CBM • Promising results for low-mass vector mesons • Excellent S/B ratio for J/ψ • GEANE for MuCh track propagation • Global tracking MuCh→TRD→ToF • Pile-up of secondary electrons • Realistic MuCh hit producer

34. Thank you for your attention!