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The C ompressed B aryonic M atter experiment

The C ompressed B aryonic M atter experiment. Claudia Höhne, GSI Darmstadt CBM collaboration. Outline physics case, observables detector layout examples on feasibility studies R&D of detector components. CBM @ FAIR.

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The C ompressed B aryonic M atter experiment

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  1. The Compressed Baryonic Matter experiment Claudia Höhne, GSI Darmstadt CBM collaboration • Outline • physics case, observables • detector layout • examples on • feasibility studies • R&D of detector components

  2. CBM @ FAIR CBM will be a high-energy heavy-ion experiment using ion beams from the SIS 300 with energies from 10-45 GeV/nucleon

  3. Physics case heat compression Q: Why do we want to build yet another heavy-ion experiment? Use heavy-ion experiments as tools in order to study the QCD phase diagram! • What does theory expect? → 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

  4. Physics case (II) • What do we know from experiment? → Heavy-ion collisions: • chemical freeze-out curve • top SPS, RHIC (high T, low mB): • partonic degrees of freedom ? • lower SPS, AGS (intermediate T-mB): • intriguing observations around 30 AGeV! • missing: • high precision measurements, systematic investigations, correlations • rare probes: charm, dileptons • → in particularly sensitive to medium! [Andronic et al. Nucl. Phys. A 772, 167 (2006).

  5. Physics case (III) Q: Why do we want to build yet another heavy-ion experiment? • complementary to RHIC, LHC: • crossover at high T, low r • rare probes! • (not accessible at low energy RHIC & SPS) • CBM@FAIR – high mB, moderate T: • searching for the landmarks of the QCD phase diagram • first order deconfinement phase transition • chiral phase transition • QCD critical endpoint • in A+A collisions from 10-45 AGeV (√sNN = 4.5 – 9.3 GeV) at FAIR! ... and investigate hadronic properties at high baryon densities

  6. Dense baryonic matter Q: Do we reach (energy and) baryon densities high and long enough in order to reach a deconfined phase? • high baryon and energy densities created in central Au+Au collisions • max. net baryon densities from 5 - 40 AGeV ~ 1 - 2 fm-3 ~ (6 – 12) r0 r = 1 fm-3 ~ 6 times normal nuclear matter density net baryon density [CBM physics group, J. Randrup priv. com.]

  7. Dense baryonic matter (II) Q: How do particles (if still existing) behave at these high baryon densities ? • hadronic properties are expected to be effected by the enormous baryon densities • → for example the r-meson is expected to melt at high baryon densities [Rapp, Wambach, Adv. Nucl. Phys. 25 (2000) 1, hep-ph/9909229] r-meson

  8. Physics topics and Observables Q: How to measure? What to look for? Sketch of U+U collision at 23 GeV/nucleon (UrQMD simulation) at different time steps initial stage high density phase "freeze-out"

  9. Physics topics and Observables rare probes! systematic measurements! → comprehensive picture with CBM as 2nd generation experiment! Q: How to measure? What to look for? • The equation-of-state at high B • collective flow of hadrons • particle production at threshold energies (open charm) • Deconfinement phase transition at high B • excitation function and flow of strangeness (K, , , , ) • excitation function and flow of charm (J/ψ, ψ', D0, D, c) • sequential melting of J/ψ and ψ', charmonium suppression • QCD critical endpoint • excitation function of event-by-event fluctuations (K/π,...) • Onset of chiral symmetry restoration at high B • in-medium modifications of hadrons (,, e+e-(μ+μ-), D) CBM Physics Book (theory) in preparation

  10. D-mesons in matter [W. Cassing, E. Bratkovskaya, A. Sibirtsev, Nucl. Phys. A 691 (2001) 745] SIS100/ 300 SIS18 HSD simulations D-meson: charm + up/down quark measure D-meson production at threshold → expectation: D-mesons sensitive to medium charm quark as probe for dense matter created at FAIR

  11. Charmonium suppression Quarkonium dissociation temperatures – Digal, Karsch, Satz • cc production • at threshold for CBM energies! • cc produced in first inelastic interactions • pp: certain probability to form a J/y (or y') • AA: dissolved in medium? • ... difference for J/y and y'? • (sequential melting?) measure energy and system-size dependence!

  12. Dileptons  n  p p  ++ K e+, μ+ r e-, μ- Dileptons are penetrating probes! • data from HADES and CERES underline the importance of baryonic resonances in this context • measure in dependence on baryon density (energy)! lifetime of r-meson 1.3 fm/c → probe the early fireball! (ct of : w – 23 fm/c, f – 44 fm/c, J/y – 2.3 fm/c)

  13. Experimental Challenge Central Au+Au collision at 25 AGeV: URQMD + GEANT3 160 p 400 -400 + 44 K+ 13 K- ... and e.g. only 10-5 – 10-4 D-mesons → high beam intensities allowing for high interaction rates, e.g. 107 Au+Au reactions/s with 1% interaction target and 109 ions/s → radiation hard and fast detectors → high speed data aquisition, efficient triggers → precision, high resolution measurements! (e.g. 50 mm vertex resolution for D-mesons)

  14. The CBM experiment MVD + STS • tracking, momentum determination, vertex reconstruction: radiation hard silicon pixel/strip detectors (STS) in a magnetic dipole field • hadron ID: TOF (& RICH) • photons, p0, m: ECAL high interaction rate long beamtime → rare probes! • PSD for event characterization • high speed DAQ and trigger • electron ID: RICH & TRD •  p suppression  104 • muon ID: absorber + detector layer sandwich •  move out absorbers for hadron runs aim: optimize setup to include both, electron and muon ID (not necessarily simultaneously)

  15. CbmRoot simulation framework • detector simulation (GEANT3) • full event reconstruction: track reconstruction, add RICH, TRD and TOF info • result from feasibility studies in the following: central Au+Au collisions at 25 AGeV beam energy

  16. STS tracking Challenge: high track density  600 charged particles in  25o • Task • track reconstruction: • 0.1 GeV/c < p  10-12 GeV/c • Dp/p ~ 1% (p=1 GeV/c) • primary and secondary vertex reconstruction (resolution  50 mm) • V0 track pattern recognition silicon pixel and strip detectors D+→ p+p+K- (ct = 317 mm) D0 → K-p+ (ct = 124 mm)

  17. Open charm production central Au+Au, 25 AGeV • D0→ K-p+ and D0 → K+p-(ct = 124 mm), full event reconstruction • <D0 + D0> = 1.5 ∙ 10-4 (central Au+Au collisions, 25 AGeV) • first pixel detector (MAPS) at 10cm • ~53 mm secondary vertex resolution • proton identification with TOF 1012 central Au+Au collisions, 25 AGeV

  18. Dileptons - electrons central Au+Au, 25 AGeV • low-mass vector mesons: try to reject large physical background (g-conversion, Dalitz decays) by high performance tracking • J/y: cut on pt (1.2 GeV/c) • high purity of electron identification needed! (p-suppr. > 104 achievable) J/y meson low-mass vector mesons S/B=1.7 eff. 12% w S/B = 0.2 eff. 7.5% 100k events = 10s of beam time 1010 events

  19. central Au+Au, 25 AGeV Dileptons - muons • low efficiency for soft muons → investigate momentum dependent m identification • phantastic J/y (pt > 1 GeV/c), even y' should be accessible • however: high hit densities in detectors! low-mass vector mesons (1.25 m Fe) J/y meson (add 1m Fe) w S/B = 0.4 eff. 1.3% eff. 20% 4∙108 events

  20. R&D on fast gas detectors • R&D on fast gas detectors for TRD • → development of a test beam facility at GSI which will become important for all sorts of detector tests! close collaboration with ALICE TRD group!

  21. R&D on Silicon Strip Sensors  4"280 µm Microstrip Sensors Tracking Stations layout studies module design

  22. R&D on fast self-triggered readout electronics micro-strip sensor close collaboration with electronics division and detector lab! NXYTER chip produced; DETNI − GSI test system under construction 128 channels readout at 32 MHz

  23. CBM collaboration China: CCNU Wuhan USTC Hefei Croatia: RBI, Zagreb Split University Univ. Mannheim Univ. Münster FZ Rossendorf GSI Darmstadt Norway: Univ. Bergen Kurchatov Inst. Moscow LHE, JINR Dubna LPP, JINR Dubna Poland: Krakow Univ. Warsaw Univ. Silesia Univ. Katowice Nucl. Phys. Inst. Krakow LIT, JINR Dubna MEPHI Moscow Obninsk State Univ. PNPI Gatchina SINP, Moscow State Univ. St. Petersburg Polytec. U. Hungaria: KFKI Budapest Eötvös Univ. Budapest Cyprus: Nikosia Univ. India: VECC Kolkata SAHA Kolkata IOP Bhubaneswar Univ. Chandigarh Portugal: LIP Coimbra Romania: NIPNE Bucharest Czech Republic: CAS, Rez Techn. Univ. Prague France: IPHC Strasbourg Ukraine: Shevchenko Univ. , Kiev Univ. Varanasi IlT Kharagpur Korea: Korea Univ. Seoul Pusan National Univ. Russia: IHEP Protvino INR Troitzk ITEP Moscow KRI, St. Petersburg Germany: Univ. Heidelberg, Phys. Inst. Univ. HD, Kirchhoff Inst. Univ. Frankfurt Univ. Kaiserslautern 47 institutions ~ 380 members Strasbourg, September 2006

  24. Summary • unique physics case: • search for the landmarks of the CQD phase diagram • comprehensive investigation of rare probes • unique opportunity at FAIR: • high beam intensity, high availability of the beam, promising energy range • sophisticated feasibility studies of key observables: • charm, dilepton measurement possible at FAIR! • R&D to solve challenging detector requirements • fast, radiation hard detectors, ultra-thin Si-detectors, fast self-triggered readout electronics, high speed data aquisition

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