Claudia Höhne GSI Darmstadt, Germany

1. The Compressed Baryonic Matter experiment at the future accelerator facility FAIR in Darmstadt Claudia Höhne GSI Darmstadt, Germany

2. Outline • FAIR • motivation for CBM • detector layout • physics topics and observables • data available so far • CBM feasibility studies • outlook

3. SIS 100 Tm SIS 300 Tm U: 35 AGeV p: 90 GeV CBM @ FAIR • Facility for Antiproton and Ion Research • „next generation“ accelerator facility: • double-ring synchrotron • simultanous, high quality, intense primary and secondary beams • cooler/ storage rings (CR, NESR, HESR) Cooled antiproton beam: hadron spectroscopy Ion and Laser induced plasmas: High energy density in matter Structure of nuclei far from stability low-energy antiproton beam: antihydrogen Compressed baryonic matter

4. critical endpoint: [Z.Fodor, S.Katz, JHEP 0404:050 (2004)] [S.Ejiri et al., hep-lat/0312006] Motivation Mapping the QCD phase diagram of strongly interacting matter with heavy ion collisions • high T, low mB •  top SPS, RHIC, LHC • low T, high mB •  SIS • intermediate range ?  low energy runs SPS, AGS  SIS 300 @ GSI ! • Highest baryon densities! • → in medium properties of hadrons • Critical point? • Deconfinement? SIS100/300

5. physics topics observables deconfinement at high rB ? softening of EOS ? strangeness production: K, L, S, X, W charm production: J/y, D flow excitation function in-medium properties of hadrons  onset of chiral symmetry restoration at high rB r, w, f e+e- open charm Critical point ? event-by-event fluctuations Physics topics and observables

6. tracking in high track density environment (~ 1000) hadron ID lepton ID myons, photons secondary vertex reconstruction (resolution  50 mm) large statistics: large integrated luminosity: high beam intensity (109 ions/sec.) and duty cycle beam available for several months per year high interaction rates (10 MHz) fast, radiation hard detector efficient trigger strangeness production: K, L, S, X, W charm production: J/y, D flow excitation function rare signals! r, w, f e+e- open charm event-by-event fluctuations detector requirements observables detector requirements & challenges Systematic investigations: A+A collisions from 8 to 45 (35) AGeV, Z/A=0.5 (0.4) (up to 8 AGeV: HADES) p+A and p+p collisions from 8 to 90 GeV

7. The CBM experiment • tracking, momentum determination, vertex reconstruction: radiation hard silicon pixel/strip detectors (STS) in a magnetic dipole field • electron ID: RICH & TRD (& ECAL)  p suppression  104 • hadron ID: TOF (& RICH) • photons, p0, m: ECAL • high speed DAQ and trigger ECAL (12 m) RICH magnet beam target TOF (10 m) STS (5, 10, 20, 40, 60, 80, 100 cm) TRDs (4,6, 8 m)

8. Silicon Pixel Detector • Requirements: • radiation hardness • low material budget: d < 200 mm • fast read out • good position resolution < 20 mm MIMOSA IV IReS/ LEPSI Strasbourg • R&D on Monolithic Active Pixel Sensors (MAPS): • pitch 20 mm • thickness < 100 mm • single hit resolution ~ 3mm • problem: radiation hardness and readout speed ( event pile up in first 2 STS) • fallback solution: hybrid detectors (problem: thickness, granularity!)

9. Silicon Strip detector Tracking Stations Nr. 4 and 6 4 Strip tracking stations Double sided Si-Strip detectors: thickness 100 μm pitch 25 μm Stereo angle 15o

10. tracking Challenge: high track density  600 charged particles in  25o

11. RICH detector design goals: electron ID for p < 10-12 GeV/c (e from low-mass vector meson decays) pion ID for p > 4-5 GeV/c: improve K/p separation for higher momenta! e/p rejection factor > 100 design: two Be+glass mirrors, r=450cm two photodetector planes, shielded by magnet yoke radiator with   38 (e.g. nitrogen =41) rings in focal plane layout RICH: side view y z (beam)

12. TRD Task: e/p separation > 100, tracking Setup: 9 layers in three stations (4m, 6m, 8m from target) area per layer 25, 50, 100 m2 • Requirements: • high counting rate (up to 150 kHz/cm2) • fast readout (10 MHz) • large area • position resolution ~ 200 mm • R&D • for outer region state-of-the art is appropriate (ALICE, ATLAS) • inner part: R&D on fast gas detectors in progress (drift chamber/ GEM/ straw tubes) • successful test of prototypes (MWPC, GEM) in July 2004 at SIS/GSI

13. TOF → RPC Challenge for TOF : high counting rate (25 kHz/cm2) large area (130 m2 @ 10 m) time resolution ~ 80 ps R&D Coimbra, Portugal prototype: single gap counters with metal and plastic electrodes (resistivity 109Wcm)

14. Design of ECAL • Design goals of sampling calorimeter: • energy resolution of 5/E (%) • high-rate capability up to 15 kHz/cm2 • e/p/(m) discrimination • total area ~200m2 • Lead-scintillator calorimeter: • 0.5 – 1 mm thick tiles • 25 X0 total length • PM read out • (see HERA-B, PHENIX, LHCb) Granularity: inner region 3x3 cm2 intermediate region 6x6 cm2 outer region 12x12 cm2 Tests of detector module prototype: July 2004 at CERN

15. self-triggered hit detection pre-processing feature extraction Detectors each hit transported as address/ timestamp/ value Frontend electronics clock Buffer pool extraction of physical signatures trigger decision storage (1Gbyte/s) Event builder and selector DAQ • Requirements • efficient detection of rare probes (D as key factor): event rate for storage 25 kHz •  reduction factor 400 needed! • fast: 1st level trigger at full design interaction rate of 10MHz •  reconstruct ~ 109 tracks/s, secondary vertices ... • data volume in 1st level trigger ~ 500 Gbytes/s • event size ~ 40kbyte essential performance limitation not latency but throughput

16. Strangeness production [C.Blume et al., nucl-ex/0409008] maximum of strangeness production at 30 AGeV

17. CBM: Particle identification by TOF simulations: central Au+Au at 25 AGeV, UrQMD GEANT3 with magnetic field, CBM setup time resolution 80ps, TOF wall in 10m distance to target Squared mass measured with TOF Mass2 distribution for p = 6 GeV/c p K π

18. CBM: improve K/p separation nitrogen radiator RICH detector with p-threshold p ~ 6 GeV/c

19. CBM: acceptance including TOF-ID yCM 15 AGeV 1.75 25 AGeV 2. 35 AGeV 2.16   

20. K/p fluctuations [C.Roland et al., nucl-ex/0403035] • dynamical fluctuations of the K/p ratio increasing towards lower energies • p/p due to resonance decays, reproduced by UrQMD

21. data mixed events CBM: dynamical fluctuations UrQMD: central Au+Au collisions at 25 AGeV

22. charm production Predictions of open charm yield for central A+A collisions differ by orders of magnitude for different production scenarios, especially at low energies [Gorenstein et al J. Phys. G 28 (2002) 2151] [W. Cassing et al., Nucl. Phys. A 691, 753 (2001)] central Au+Au

23. D0 K-,+signal Background Reconstructed events Z-vertex(cm) CBM: D0→ K-p+ (ct = 124mm) Simulations: UrQMD (incl. hyperons) + D meson track reconstruction (Kalman filter) without magnetic field, dp/p = 1%

24. CBM: online event selection of D0 using track information from Silicon Tracker only (no particle ID) secondary vertex resolution 57mm (no magnetic field), 65mm (magnetic field) event reduction by factor 1000: 10 MHz  10 kHz (no magnetic field so far!) D0+ D0 multiplicity from HSD: 1.5·10-4 per central Au+Au event at 25 AGeV

25. 10 50 120 210 Elab [GeV] J/ production central collisions 25 AGeV Au+Au 158 AGeV Pb+Pb J/ multiplicity 1.5·10-5 1·10-3 beam intensity 1·109/s 2·107/s interactions 1·107/s (1%) 2·106/s (10%) central collisions 1·106/s 2·105/s J/ rate 15/s 200/s 6% J/e+e- (+-) 0.9/s 12/s spill fraction 0.8 0.25 acceptance 0.25  0.1 J/ measured 0.17/s  0.3/s  1·105/week 1.8·105/week

26. p-suppression 10-4 CBM: charmonium measurement e+e- e+e- channel (m+m- also under investigation) assumptions: ideal tracking momentum resolution 1% 2·1010 central Au + Au UrQMD 25 AGeV + GEANT3 different p-suppression, pt> 1 GeV p-suppression 10-4 10-2 10-3 10-4 no p (red)

27.    → e+e- CERES [Phys. Rev. Lett. 91, 042301 (2003)] • enhancement of low-mass dilepton pairs, larger at 40 AGeV compared to 158 AGeV • in medium modification of r ?

28. CBM: low mass e+e- pairs problem: tracking and momentum determination for low momenta (p < 2 GeV)?  so far only generic study assuming ideal tracking, no magnetic field Background: URQMD Au+Au 25 AGeV + GEANT3 • Cuts: • 1. remove low-mass pairs • 2. single electron: • pt > 0.1 GeV/c • d < 50 mm • 3. electron pair: • vz < 0.1 cm • vt< 0.01 cm • D < 0.01 cm • Θ> 10° included: 0.01% misidentified pions 90% electron efficiency

29. D-mesons in medium [W. Cassing, E. Bratkovskaya, A. Sibirtsev, Nucl. Phys. A 691 (2001) 745] SIS100/ 300 SIS18

30. Outlook • detector design and optimization • R&D on detector components • feasibility studies of key observables • CBM collaboration formed and still increasing • technical Status Report submitted in January 2005 • be ready in 2014 for new and exciting physics!

31. CBM collaboration Croatia: RBI, Zagreb Cyprus: Nikosia Univ. Czech Republic: Czech Acad. Science, Rez Techn. Univ. Prague France: IReS Strasbourg Germany: Univ. Heidelberg, Phys. Inst. Univ. HD, Kirchhoff Inst. Univ. Frankfurt Univ. Mannheim Univ. Marburg Univ. Münster FZ Rossendorf GSI Darmstadt Romania: NIPNE Bucharest Russia: CKBM, St. Petersburg IHEP Protvino INR Troitzk ITEP Moscow KRI, St. Petersburg Kurchatov Inst., Moscow LHE, JINR Dubna LPP, JINR Dubna LIT, JINR Dubna PNPI Gatchina SINP, Moscow State Univ. Spain: Santiago de Compostela Univ. Ukraine: Univ. Kiev Hungaria: KFKI Budapest Eötvös Univ. Budapest Italy: INFN Frascati Korea: Korea Univ. Seoul Pusan National Univ. Norway: Univ. Bergen Poland: Jagiel. Univ. Krakow Silesia Univ. Katowice Warsaw Univ. Warsaw Tech. Univ. Portugal: LIP Coimbra