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Soft muon identification

Soft muon identification. Anna Kiseleva GSI Germany, PNPI Russia. Results of the last collaboration meeting (ρ 0 , ω, φ, J/ψ) The low-mass vector meson problem (soft muons) acceptance of ρ 0 at MUCH possible solution results Absorber study: motivation Outlook.

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Soft muon identification

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  1. Soft muon identification Anna Kiseleva GSI Germany, PNPI Russia • Results of the last collaboration meeting (ρ0, ω, φ, J/ψ) • The low-mass vector meson problem (soft muons) • acceptance of ρ0 at MUCH • possible solution • results • Absorber study: motivation • Outlook

  2. CBM detector: e+e- setup ECAL TRD1 TOF RICH TRD3 TRD2 STS STS: track and vertex reconstruction RICH: electron identification. TRD: identification of high-energy electrons RPC-TOF: time-of-flight measurement ECAL: electron and photon identification

  3. CBM detector: μ+μ- setup ECAL TOF TRD3 TRD1 TRD2 MUCH STS

  4. 5 10 20 30 120 cm STS Fe C MUonCHamber system (MUCH) • First design study • absorbers: • 4 Fe + 1 C • increasing thickness • full thickness ~ 1m Fe • detectors: • 2 layers between absorbers • 1 – in front of MUCH • 2 – behind last absorber

  5. Tracks π- π+ 1 central Au+Au event at 25 AGeV beam energy (top view of the STS + MUCH system)

  6. Yields for central Au+Au at 25 AGeV multiplicity branching ratio of  channel per event

  7. J/ψ ω φ ρ0 Invariant mass spectra • full STS tracking: • STS digitization • track finding • momentum reconstruction • primary vertex cut • MUCH tracking: • 100μm position resolution • STS track extrapolation • track finding and matching

  8. J/ψ acceptance 4π sts much 1m Fe pt> 1GeV/c sts: > 4 sts hits much: sts + first much 1m Fe: behind 1m Fe

  9. 6% 2.599 2% 2.438 2% 2.424 0.3% 2.255 10.5% 2.525 8.5% 2.55 8% 2.525 11% 2.525 Acceptance of RECO ρ0 1 2 3 4 2 hard μμ 1hard + 1soft μμ 1hard + 1soft-soft μμ  2 soft μμ 1+2 1+2+3 1+2+3+4 1+2+4 3000 ρ0➙μ+μ- 5 6 7 8

  10. ρ0 acceptance 4π sts much 1m Fe sts: > 4 sts hits much: sts + first much 1m Fe: behind 1m Fe

  11. Momentum distribution much 1m Fe

  12. Momentum Dependent Track Selection (MDTS)

  13. MUCH detector model for MDTS study 25 Fe × 5cm p  [0.5, 1.5] GeV/c μ- π- μ+ π+

  14. Δabsorber cm MUCH detector model for MDTS study 25 Fe × 5cm p  [0.5, 1.5] GeV/c

  15. Absorber thickness vs. momentum π+, π- μ+, μ- absorber thickness, cm absorber thickness, cm

  16. Absorber thickness vs. momentum p = 1 GeV/c counts ● π+, π- ■μ+, μ-

  17. N of hits at the MUCH system: ρ0➙μ+μ- NMUCH hitsμ- 5 μ- 4 3 2 ρ0 μ+ 5 7 NMUCH hitsμ+ 9 11

  18. Type of muon pairs 2 hard muons μ+ ρ0 μ- 65 cm ~ 1m Fe p (GeV/c)

  19. Type of muon pairs 1 hard + 1 soft muons μ+ ρ0 μ- 65 cm ~ 1m Fe p (GeV/c)

  20. Type of muon pairs 1 hard + 1 soft-soft muons μ+ ρ0 μ- 35 65 cm ~ 1m Fe p (GeV/c)

  21. Type of muon pairs 2 soft muons μ+ ρ0 μ- 65 cm ~ 1m Fe p (GeV/c)

  22. MDTS: possible pairs NMUCH hitsμ- 2 hard muons 1hard + 1soft muons 1hard + 1soft-soft muons 2 soft muons NMUCH hitsμ+

  23. ρ0 acceptance 2 hard μμ 1hard + 1soft μμ 1hard + 1soft-soft μμ 2 soft μμ

  24. MDTS: possible pair combinations NMUCH hitsμ- 2 hard muons 1hard + 1soft muons 1hard + 1soft-soft muons 2 soft muons NMUCH hitsμ+

  25. MDTS: possible pair combinations NMUCH hitsμ- 2 hard muons 1hard + 1soft muons 2 soft muons NMUCH hitsμ+

  26. ρ0 acceptance 1 + 2 1 + 2 + 3 2 hard μμ 1hard + 1soft μμ 1hard + 1soft-soft μμ 2 soft μμ 1 + 2 + 3 + 4 1 + 2 + 4

  27. Reconstruction • full STS tracking: • STS digitization • track finding • momentum reconstruction • primary vertex cut • MUCH tracking: • 100μm position resolution • STS track extrapolation • track finding and matching

  28. RECO background 2 hard μμ 1hard + 1soft μμ 1hard + 1soft-soft μμ  2 soft μμ 1+2 1+2+3 1+2+3+4 1+2+4

  29. ω➙μ+μ- : S/B ratio S/B 2 hard μμ 1hard + 1soft μμ 1hard + 1soft-soft μμ  2 soft μμ 1+2 1+2+3 1+2+3+4 1+2+4

  30. Invariant mass spectra 2 hard μμ 2 hard μμ + 1hard + 1soft μμ 2 hard μμ + 1hard + 1soft μμ + 2 soft μμ ■ρ ■ω ■φ ■ρ ■ω ■φ ■ρ ■ω ■φ counts/(events×10GeV/c2) minv (GeV/c2)

  31. Outlook • Tuning of momentum dependent muon identification • Study of different absorber materials, for example tungsten (W)

  32. Absorber study: preliminary results MUCH detector behind 5cm W

  33. Fe Fe Fe Fe Fe W W W W W W Fe Fe Fe Fe W W Fe Fe Fe Hit density of central UrQMD event 5cm

  34. Thank you for your attention!

  35. ρ0 parameters opening angle (°) transverse momentum (GeV/c) scalar product (GeV/c)2 ρ0 bg bg ρ0➙μ+μ-

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