1 THE MUON DETECTION SYSTEM FOR THE CBM EXPERIMENT AT FAIR/GSI A. Kiseleva Helmholtz International Summer School Dense Matter In Heavy Ion Collisions and Astrophysics (DM2008) July 14 – 26, 2008

2 Outline FAIR project CBM experiment: – – setup – – observables The muon detection system for CBM – – layout – – feasibility studies for: ρ, ω, φ J/ψ Conclusions and next steps

3 FAIR: the international Facility for Antiproton and Ion Research GSI: Gesellschaft für Schwerionenforschung GSI/FAIR

4 FAIR: the international Facility for Antiproton and Ion Research storage and cooler rings beams of rare isotopes e – A Collider stored and cooled antiprotons GeV primary beams 5∙10 11 /s; GeV/u; 238 U 28+ factor increased intensity 4x10 13 /s 90 GeV protons /s 238 U 35 GeV/u (Ni 45 GeV/u) secondary beams rare isotopes GeV/u; factor increased intensity antiprotons 3(0) - 30 GeV accelerator technical challenges rapidly cycling superconducting magnets high energy electron cooling dynamical vacuum, beam losses

5 Research programs at FAIR Rare isotope beams: nuclear structure and nuclear astrophysics nuclear structure far off stability nucleosynthesis in stars and supernovae Beams of antiprotons: hadron physics quark-confinement potential search for gluonic matter and hybrids hypernuclei Nucleus-nucleus collisions: compressed baryonic matter baryonic matter at highest densities (neutron stars) phase transitions and critical endpoint in-medium properties of hadrons Short-pulse heavy ion beams: plasma physics matter at high pressure, densities, and temperature fundamentals of nuclear fusion Atomic physics, FLAIR, and applied research highly charged atoms low energy antiprotons radiobiology Accelerator physics high intensive heavy ion beams dynamical vacuum rapidly cycling superconducting magnets high energy electron cooling CBM experiment Nucleus-nucleus collisions: compressed baryonic matter baryonic matter at highest densities (neutron stars) phase transitions and critical endpoint in-medium properties of hadrons

6 Physics case crossover transition from partonic to hadronic matter at small  B and high T critical endpoint in intermediate range of the phase diagram first order deconfinement phase transition at high  B but moderate T heat compression Predictions from lattice QCD:

7 CBM physics topics and abservables In-medium modifications of hadrons In-medium modifications of hadrons onset of chiral symmetry restoration at high densities ρ B onset of chiral symmetry restoration at high densities ρ B measure: ρ, ω, φ → e + e - / μ + μ - measure: ρ, ω, φ → e + e - / μ + μ - open charm (D mesons) open charm (D mesons) Strangeness in matter (strange matter?) Strangeness in matter (strange matter?) enhanced strangeness production ? enhanced strangeness production ? measure: K, Λ, Σ, Ξ. Ω measure: K, Λ, Σ, Ξ. Ω Indications for deconfinement at high ρ B Indications for deconfinement at high ρ B anomalous charmonium suppression ? anomalous charmonium suppression ? measure: J/ψ, ψ' → e + e - / μ + μ -, D 0 → Kπ, D ± → Kππ measure: J/ψ, ψ' → e + e - / μ + μ -, D 0 → Kπ, D ± → Kππ softening of EOS softening of EOS measure flow excitation function measure flow excitation function Critical point event-by-event fluctuations Color superconductivity Color superconductivity precursor effects ? precursor effects ?

8 Dilepton sources in heavy-ion collisions Searching for the onset of deconfinement Investigation of dense baryonic matter using penetrating probes shift? broadening? melting?...? In-medium modifications of low-mass vector mesons: J/ψ dissociation in the QGP ? sequential melting of ψ’ and J/ψ ? modifications of p t distribution ? collective flow of charmonium ? …?

9 Yields for central Au+Au at 25 AGeV J/ψ (3095 MeV) ρ 0 (770 MeV) ω (782 MeV) φ (1020 MeV) 1.95× %4.6× × ×10 -4 ~1×10 -6 ~1× × ×10 -4 multiplicity branching ratio (μμ) yield per event φ J/ψ π+π+π+π+ CBM pion-to-charmonium ratio ~ 10 9 ! W. Cassing, E. Bratkovskaya, A. Sibirtsev Nucl. Phys. A 691 (2001) 745

10 Experimental requirements high statistics high statistics large signal-to-background ratio large signal-to-background ratio good mass resolution good mass resolution large acceptance large acceptance high reconstruction efficiency high reconstruction efficiency 160 p 400   + 44 K + 13 K - Central Au+Au collision at 25 AGeV (UrQMD + GEANT3) up to 10 7 Au+Au reactions/sec (beam intensities up to 10 9 ions/s with 1 % interaction target) determination of (displaced) vertices with high resolution (  50  m) identification of leptons and hadrons

11 CBM for dimuon measurements STSMuChTRDToF STS track, vertex and STS track, vertex and momentum reconstruction momentum reconstruction MuCh muon identification MuCh muon identification TRD global tracking TRD global tracking RPC-ToF time-of-flight measurement RPC-ToF time-of-flight measurement Measurements: charmonium – standard MuCh (13.5λ I ) low-mass vector mesons – compact MuCh (7.5λ I ) GEANT3 model STS

12 Muon detector segmentation max pad 44.8  44.8 mm 2 space resolution: x – 12.8 mm, y – 12.8 mm min pad 1.4  2.8 mm 2 space resolution: x – 400 μm, y – 800 μm Mikhail Ryzhinskiy, Saint-Petersburg State Polytechnical University 5% occupancy

13 Simulations Signals: multiplicities from Hadron-String Dynamics (HSD) – – ρ, ω, φ, η and η Dalitz – – J/ψ, Ψ' Background: Ultrarelativistic Quantum Molecular Dynamics (UrQMD) – – central Au+Au at 25 AGeV

14 Muon reconstruction J/ψ μ+μ+ μ-μ- S. Gorbunov, Kirchhoff Inst. f. Physik, Universität Heidelberg I. Kisel, GSI

15 Results Signal-to- Efficiency Mass Background (%) resolution Background (%) resolution (S/B) ratio (MeV) (S/B) ratio (MeV) ω ω φ φ J/ψ J/ψ Ψ' Ψ' Central Au+Au collisions at 25 AGeV signals  J/ψ  Ψ' signals  J/ψ  Ψ'  background signals  ρ  ω  φ  η  η Dalitz signals  ρ  ω  φ  η  η Dalitz  background

16 Analysis of background composition compact MuCh (7.5λ I )standard MuCh (13.5λ I ) Masse of particles: μ – 106 MeV, π – 140 MeV, Κ – 498 MeV, p – 938 MeV Central Au+Au collisions at 25 AGeV

17 Background rejection via mass determination m 2 = β = γ = m 2 = P 2  ( - 1) L c × t √1 – β 2 1 (β × γ) 2 P2P2 β2β2 1 (L, t) → β ToF m 2 (GeV 2 /c 4 ) P (GeV/c)

18 Improved results with pID ToF 6   without ToFwith ToF Central Au+Au collisions at 25 AGeV compact MuCh (7.5λ I ) S/B ratio eff.% S/B ratio eff.% ωφωφ

19 Results for different collision systems central 25 AGeV central 8 AGeV central 30 AGeV ω ToF pID J/ψ ω ToF pID J/ψ ω S/B (0.09)* –11147 ε, % (1.2)* –423 * in order to increase the acceptance of reconstructed ω we can use different type of tracks

20 Study of possible detector solutions Detector requirements: high rate capability (up to 1 MHz/cm 2 ) high rate capability (up to 1 MHz/cm 2 ) high granularity (up to 1 hit/cm 2 s -1 for central Au+Au collisions) high granularity (up to 1 hit/cm 2 s -1 for central Au+Au collisions) position resolution < 300 μm position resolution < 300 μm Detector options: GEM () GEM (Gas Electron Multiplier) Micromegas ( Micromegas (Micro Mesh Gaseous Detector)

21 Detector prototypes: GEMs LHE JINR Dubna PNPI St. Petersburg VECC Kolkata Support structure Pads Fasteners Spacer PCB Readout electronics Argon GEM foils

22 Conclusions Promising results for low-mass vector mesons Promising results for low-mass vector mesons Good result for J/ψ Good result for J/ψ ψ' identification seems possible ψ' identification seems possible

23 Next steps Implementation of muon trigger Implementation of muon trigger Realistic detector response: Realistic detector response: –clustering –realistic detector inefficiency Muon system optimization: Muon system optimization: –necessary number of detector layers –additional absorber in STS –detector resolution study

24 Thank you for your attention! China Croatia Cyprus Czech Republic France Germany Hungaria India Korea Norway Poland Portugal Romania Russia Ukraine China Croatia Cyprus Czech Republic France Germany Hungaria India Korea Norway Poland Portugal Romania Russia Ukraine 52 institutions, more than 400 members (May 2008)

25 Backup

26 Signal acceptance J/ψ→μ + μ - ρ→μ + μ - Pluto STS 1m Fe Central Au+Au collisions at 25 AGeV

27 Signal parameters: J/ψ J/ψ Bg J/ψ 2 (central Au+Au at 25AGeV)

28 Signal parameters: ρ 0 ρ0ρ0 Bg ρ0ρ0 2 (central Au+Au at 25AGeV)

29 Hard-soft pairs ρ 0 →μ + μ - — hard-hard (h-h) pairs — hard-soft (h-s) pairs — h-h + h-s μ hard μ soft

30 Digitization algorithm primary electrons sec. electrons Advanced digitization and cluster finding in MuCh, M. Ryzhinskiy