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Vector meson study for the CBM experiment at FAIR/GSI

Vector meson study for the CBM experiment at FAIR/GSI. Anna Kiseleva GSI Germany, PNPI Russia. Motivation The muon detection system of CBM Vector meson identification (ρ 0 , ω, φ, J/ψ) The low-mass vector meson problem (soft muons) acceptance of ρ 0 at MUCH

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Vector meson study for the CBM experiment at FAIR/GSI

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  1. Vector meson study for the CBM experiment at FAIR/GSI Anna Kiseleva GSI Germany, PNPI Russia • Motivation • The muon detection system of CBM • Vector meson identification (ρ0, ω, φ, J/ψ) • The low-mass vector meson problem (soft muons) • acceptance of ρ0 at MUCH • possible solution • preliminary results • Outlook

  2. Dilepton Sources in Heavy-Ion Collisions Signatures of the quark-gluon plasma: anomalous suppression of charmonium In-medium spectral function using penetrating probes

  3. Di-electron measurements(CERES/CERN) Calculations by R. Rapp: thick dashed line: unmodified rho thick dashed-dotted line: in-medium dropping rho mass thick solid line: in-medium spread rho width D.Adamova et al., PRL 91 (2003) 042301

  4. Di-muon measurements(NA60) In+In 158 AGeV 5-week-long run in Oct.–Nov. 2003 ~ 4 × 1012 ions delivered in total

  5. CBM detector: e+e- setup A+A collisions at 10 – 45 AGeV 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

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

  7. 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

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

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

  10. Bg  p+  p- Cuts for background suppression Single particle cut: transverse momentum pt J/ψμ+μ- μ+ pt J/ψ z Bg pt μ- GeV/c J/ψμ+μ-

  11. μ+ J/ψ  z μ-   p- p+•   p+ p+   p- p- Cuts for background suppression Pair cuts: 1. opening angle  J/ψμ+μ- Bg º 2. scalar product J/ψμ+μ- μ+ J/ψ z Bg μ- (GeV/c)2

  12. Comparison of J/ψ to ρ0 opening angle (°) transverse momentum (GeV/c) scalar product (GeV/c)2 J/ψ Bg ρ0 Bg Bg J/ψμ+μ- ρ0μ+μ-

  13. 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

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

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

  16. Momentum distribution much 1m Fe 1.3 1.3

  17. Momentum Dependent Track Selection (MDTS)

  18. MUCH detector model for MDTS study μ- π- μ+ π+

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

  20. Application: preliminary results 2 hard muons μ+ ρ0 μ- 65 cm ~ 1m Fe

  21. μ+ Application: preliminary results 1 hard + 1 soft muons ρ0 μ- 65 cm ~ 1m Fe

  22. Application: preliminary results μ+, μ- π+, π- 100 absorber thickness, cm 65 0.9 1.3

  23. Application: preliminary results J.Vassiliev full STS and MUCH tracking 2 hard muons 1 soft + 1 hard muon

  24. ρ0 acceptance J.Vassiliev 2.234 2.231 2 hard muons 2.477 1 soft + 1 hard muon

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

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