Vector meson identification via dimuon measurements at CBM/FAIR

1. Vector meson identification via dimuon measurements atCBM/FAIR A. Kiseleva Gesellschaft für Schwerionenforschung mbH, Darmstadt International conference «NUCLEUS-2007» Voronezh, Russia, June 25 – 29, 2007

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 primary beams • 5∙1011/s; 1.5-2 GeV/u; 238U28+ • factor 100-1000 increased intensity • 4x1013/s 90 GeV protons • 1010/s 238U 35 GeV/u (Ni 45 GeV/u) secondary beams • rare isotopes 1.5 - 2 GeV/u; • factor 10 000 increased intensity • antiprotons 3(0) - 30 GeV storage and cooler rings accelerator technical challenges • beams of rare isotopes • e – A Collider • 1011 stored and cooled antiprotons • 0.8 - 14.5 GeV • 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 • Nucleus-nucleus collisions: compressed baryonic matter • baryonic matter at highest densities (neutron stars) • phase transitions and critical endpoint • in-medium properties of hadrons CBM experiment

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

7. Dilepton sources in heavy-ion collisions Investigation of dense baryonic matter using penetrating probes In-medium modifications of low-mass vector mesons: • shift ? • broadening ? • melting ? • ... ? Searching for the onset of deconfinement • J/ψ dissociation in the QGP ? • sequential melting of ψ’ and J/ψ ? • modifications of pt distribution ? • collective flow of charmonium ? • … ?

8. Experimental requirements • high statistics • large signal-to-background ratio • good mass resolution • large acceptance • high reconstruction efficiency Central Au+Au collision at 25 AGeV (UrQMD + GEANT4) 160 p 400 - 400 + 44 K+ 13 K- • up to 107 Au+Au reactions/sec (beam intensities up to 109 ions/s with 1 % interaction target) • determination of (displaced) vertices with high resolution ( 50 m) • identification of leptons and hadrons

9. Yields for central Au+Au at 25 AGeV CBM π+ φ J/ψ multiplicity branching ratio (μμ) pion-to-charmonium ratio ~ 109 ! yield per event W. Cassing, E. Bratkovskaya, A. Sibirtsev Nucl. Phys. A 691 (2001) 745

10. CBM for dimuon measurements ECAL ToF Fe Fe Fe Fe Fe TRD3 20 20 20 30 35 cm TRD2 TRD1 MuCh STS STS track, vertex and momentum reconstruction MuCh muon identification TRD identification of high-energy electrons, global tracking RPC-ToF time-of-flight measurement ECAL electron and photon identification

11. Muon detector segmentation 5% occupancy min pad 1.4  2.8 mm2 space resolution: x – 400 μm, y – 800 μm max pad 44.8  44.8 mm2 space resolution: x – 12.8 mm, y – 12.8 mm Mikhail Ryzhinskiy, Saint-Petersburg State Polytechnical University

12. Simulations • Signals: multiplicities from The Hadron-String Dynamics (HSD) • ρ, ω, φ, η and ηDalitz • J/ψ, Ψ' • Background: The Ultrarelativistic Quantum Molecular Dynamics (UrQMD) • central Au+Au at 25 AGeV www.th.physik.uni-frankfurt.de/~brat/hsd.html www.th.physik.uni-frankfurt.de/~urqmd/

13. Muon reconstruction μ+ ρ μ- S. Gorbunov, GSI I. Kisel, Kirchhoff Inst. f. Physik, Universität Heidelberg

14. signals ρ ω φ η ηDalitz S/B ratio eff. (%) ω 0.11 4 φ 0.06 7 ρ0.002 2.8 S/B ratio eff. (%) J/ψ 18 13 Ψ' 0.8 16 Results

15. Preliminary results of detector segmentation study S/B = 0.15, eff. = 2.2 % min pad 1.4  2.8 mm2 space resolution: x – 400 μm, y – 800 μm max pad 44.8  44.8 mm2 space resolution: x – 12.8 mm, y – 12.8 mm min pad 0.35  0.7 mm2 space resolution: x – 100 μm, y – 200 μm max pad 11.2  11.2 mm2 space resolution: x – 3.2 mm, y – 3.2 mm small pads S/B = 0.37, eff. = 2.1 %

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

17. Next steps • Continue of detector layout study • Study of possible muon system solution: • detector requirements: • high rate capability (up to 1 MHz/cm2) • high granularity (up to 1 hit/cm2s-1 for central Au+Au collisions) • position resolution < 300 μm • detector options: • GEM(Gas Electron Multiplier) • Micromegas(Micro Mesh Gaseous Detector)

18. China Croatia Cyprus Czech Republic France Germany Hungaria India Korea Norway Poland Portugal Romania Russia Ukraine CBM Thank you for your attention! 47 institutions, more than 400 members (April 2007) www.gsi.de/fair/experiments/CBM/index.html