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The C ompressed B aryonic M atter experiment at the future accelerator facility in Darmstadt

The C ompressed B aryonic M atter experiment at the future accelerator facility in Darmstadt. Claudia Höhne GSI Darmstadt, Germany. RHIC. SPS. SIS300. hadronic phase. nuclei. Motivation. Phase diagram of strongly interacting matter.

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The C ompressed B aryonic M atter experiment at the future accelerator facility in Darmstadt

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

  2. RHIC SPS SIS300 hadronic phase nuclei Motivation Phase diagram of strongly interacting matter lattice QCD : Fodor / Katz, Nucl. Phys. A 715 (2003) 319 • 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 • Critical point? • Deconfinement? dense baryonic medium dilute hadron gas

  3. Motivation Phase diagram of strongly interacting matter SIS300 light, heavy ions • 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 • Critical point? • Deconfinement? and region of maximum of relative strangeness production

  4. critical point * mq/T=1 Motivation • recent improvements in lattice-QCD allow for calculations at finite mB : • large baryon-number density fluctuations at the phase border for mq/T=1 • critical point at TE=162  2 MeV, mE=360  40 MeV * •  intermediate range of phase diagram! [Allton et al., Phys. Rev. D68, 014507 (2003)] [Allton et al., Phys. Rev. D66, 074507 (2002)] *[Fodor, Katz, JHEP 0404, 050 (2004)]

  5. Known so far ... Low energy run at SPS (20, 30, 40 AGeV): Relative strangeness production shows ... [J. Phys. G 30, 701 (2004)] [J. Phys. G 30, 1381 (2004)] NA49 NA49 • sharp maximum in energy dependence: transition from hadronic to partonic phase? • dynamical fluctuations which increase towards lower energies: critical point?

  6. Known so far ... Low energy run at SPS (40 AGeV): r, w, f 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 ? •  need more and better measurements also at lower energies!

  7. K+ RBBU KN Pot. no KN Pot. Known so far ... A+A collisions at SIS : strangeness production in medium KAOS Collaboration [M. Lutz, Phys. Lett. B 426, 12 (1998)] • experimental evidence for modification of kaon energy in medium! • yields, rapidity spectra, azimuthal distributions ...

  8. Open questions ... various QCD inspired models predict a change of the D-mass in a hadronic medium [Mishra et al ., Phys. Rev. C 69, 015202 (2004) ] • in analogy to kaon mass modification, but drop for both, D+ and D- • substantial change (several 100 MeV) already at =0 • effect for charmonium is substantially smaller

  9. Open questions ... Consequence of reduced D mass: DD threshold drops below charmonium states [Mishra et al., Phys. Rev. C 69, 015202 (2004) ] • decay channels into DD open for ’, c, J/y • broadening of charmonium states • suppression of J/y  lepton pair channel (large fraction of J/y from higher states) • (slight) enhancement of D mesons

  10. Open questions ... ... but even charm production near threshold is not known [Gorenstein et al J. Phys. G 28 (2002) 2151] Predictions of open charm yield for central A+A collisions differ by orders of magnitude for different production scenarios, especially at low energies [W. Cassing et al., Nucl. Phys. A 691, 753 (2001)] central Au+Au

  11. 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 CBM experiment

  12. 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 CBM experiment observables detector requirements tracking in high track density environment (~ 1000) hadron ID lepton ID myons, photons secondary vertex reconstruction (resolution  50 mm) large statistics: high beam intensity (109 ions/sec.) high interaction rates (10 MHz) fast, radiation hard detector efficient trigger all-in-one device suitable for every purpose

  13. CBM detector layout • tracking, vertex reconstruction: radiation hard silicon pixel/strip detectors (STS) in a magnetic dipole field • electron ID: RICH1 & TRD (& ECAL)  p suppression  104 • hadron ID: TOF (& RICH2) • photons, p0, m: ECAL • high speed DAQ and trigger ECAL RICHs magnet beam TOF TRDs target STS

  14. 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 Compressed baryonic matter

  15. Tracking with STS • Experimental conditions: • 5cm (1st STS) up to 2 hits/mm2 per event • 100cm (7th STS) < 0.01 hits/mm2 •  7 planar layers of pixel/ strip detectors: • high precision vertex reconstruction: 2 pixel layers at 5cm, 10 cm downstream of target • fast strip detectors for outer stations (20, 40, 60, 80, 100 cm from target) fraction of reconstructed tracks Reconstruction efficiency > 95 % Momentum resolution ≈ 0.6 % p [GeV/c]

  16. STS • 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!)

  17. electron ID with RICH 1 radiator gas: N2 gth = 41 , pp,th = 5.7 GeV/c  (almost) hadron blind photodetectors: photomultipliers (or gas detectors) aim: p suppression ~ 104 - 103 p-spectrum at for central Au+Au collision at 25 AGeV (UrQMD)

  18. RICH 1 two mirrors: beryllium covered with glass, R = 450 cm two focal planes (3.6 m2 each) separated vertically, shielded by magnet yoke layout RICH: side view rings in focal plane y z (beam)

  19. 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 p efficiency < 1% reachable with 9 layers: • Requirements: • high counting rate (up to 150 kHz/cm2) • fast readout (10 MHz) • large area • position resolution ~ 200 mm • R&D • for most of the system state-of-the art is appropriate (ALICE) • inner part: R&D on fast gas detectors in progress (drift chamber/ GEM/ straw tubes)

  20. Hadron ID with TOF identification probability of K- for sTOF = 80 ps bulk of hadrons (p, K, p) can be well identified with sTOF = 80 – 100 ps

  21. RPC as TOF detector 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)

  22. RICH 2 (?) Kaon ID by TOF quickly deteriorates above 4 GeV identification probability of K- for sTOF = 80 ps Momentum distribution of kaons from D0 decays Kaon ID by RICH for p > 4 GeV would be desirable Option for RICH2 ? e.g. thr = 30  p,thr = 4.2 GeV, pK,thr=15 GeV problem: ring finding in high hit density environment

  23. 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 & trigger architechture • Requirements • efficient detection of rare probes (D, J/y, low-mass dilepton pairs): event rate 25 kHz •  evaluation of complex signatures • fast: 1st level trigger at full design interaction rate of 10MHz •  reconstruct ~ 109 tracks/s, secondary vertices ... • data volume in 1st level trigger ~ 50 Gbytes/s • event size ~ 40kbyte essential performance limitation not latency but throughput

  24. Feasibility Study: D0 D0 K-p+ (ct=124.4 mm, BR 3.9  0.1%) Key variable to suppress background: secondary vertex position central Au+Au @ 25 AGeV (HSD): <D0> ~ 10-3 simulation including various cuts (vz !)  S/B ~ 1  detection rate ~ 13k/h at 1MHz interaction rate • Crucial detector parameters • material in STS • single hit resolution

  25. Feasibility Study: J/y  e+e- extremely rare signal (central Au+Au @ 25 AGeV ~ 10-5 /event) 6% branching ratio  e+e- background from various sources: conversion, Dalitz decays of p0 and h, r, misidentified p, ... very efficient cut on single electron pt, pair opening angle S/B > 1 should be feasible

  26. Feasibility Study: r, w, f e+e- branching ratio ~ 4.44 10-5 (r) – 3.1 10-4 (f) background from various sources: conversion, Dalitz decays of p0 and h, misidentified p, ... no easy pt-cut as for J/y  sophisticated cutting strategy necessary depends crucially on elimination of conversion pairs by tracking and charged pion discrimination by RICH and TRD ( 104 !) • idealized simulation: • no momentum resolution • no p misidentification • cut on pt, pair opening angle, prim. vertex track • S/B 0.5-1

  27. Status of project • So far ... • November 2001 Conceptual Design Report, Cost estimate 675 M € • July 2002 German Wissenschaftsrat recommends realisation • February 2003 German Federal Gouvernment decides to build the facility, will pay 75% • January 2004 CBM Letter of Intent submitted • CBM collaboration is formed: 250 scientiest from 39 institutions • work in progress: detector design and optimization • R&D on detector components • feasibility studies of key observables • next step: Technical Proposal January 2005 • could run in 2012!

  28. 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

  29. CBM time schedule Milestones: 1. Technical Proposal begin of 2005 2. Technical Design Report end of 2007

  30. experimental conditions Hit rates for 107 minimum bias Au+Au collisions at 25 AGeV: Rates of > 10 kHz/cm2 in large part of detectors !  main thrust of our detector design studies

  31. CBM R&D working packages Feasibility, Simulations Design & construction of detectors Data Acquis., Analysis GEANT4:GSI Silicon Pixel IReS Strasbourg Frankfurt Univ., GSI Darmstadt, RBI Zagreb, Univ. Krakow Fast TRD JINR-LHE, Dubna GSI Darmstadt, Univ. Münster INFN Frascati Trigger, DAQ KIP Univ. Heidelberg Univ. Mannheim GSI Darmstadt JINR-LIT, Dubna Univ. Bergen KFKI Budapest Silesia Univ. Katowice Univ. Warsaw ,ω, e+e- Univ. Krakow JINR-LHE Dubna Straw tubes JINR-LPP, Dubna FZ Rossendorf FZ Jülich Tech. Univ. Warsaw D  Kπ(π) GSI Darmstadt, Czech Acad. Sci., Rez Techn. Univ. Prague Silicon Strip SINP Moscow State U. CKBM St. Petersburg KRI St. Petersburg Analysis GSI Darmstadt, Heidelberg Univ, J/ψ e+e- INR Moscow ECAL ITEP Moscow GSI Darmstadt Univ. Krakow RPC-TOF LIP Coimbra, Univ. Santiago de Com., Univ. Heidelberg, GSI Darmstadt, Warsaw Univ. NIPNE Bucharest INR Moscow FZ Rossendorf IHEP Protvino ITEP Moscow Hadron ID Heidelberg Univ, Warsaw Univ. Kiev Univ. NIPNE Bucharest INR Moscow RICH IHEP Protvino GSI Darmstadt Magnet JINR-LHE, Dubna GSI Darmstadt Tracking KIP Univ. Heidelberg Univ. Mannheim JINR-LHE Dubna

  32. Acceptance of D0 and J/y D0 J/ψ pt [GeV/c]

  33. p misidentification 0 % 0.01 % 0.1 % 1 %

  34. 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 of 25-200 • total area ~200m2 • Lead-scintillator calorimeter: • 0.5 – 1 mm thick tiles • 25 X0 total length • PM read out Distance between electron and closest track in the innermost region Granularity: inner region 2x2 cm2 intermediate region 5x5 cm2 outer region 10x10 cm2 Tests of detector module prototype: July 2004 at CERN

  35. FAIR @ GSI

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