The Compressed Baryonic Matter (CBM) experiment at FAIR

1
The Compressed Baryonic Matter (CBM) experiment
at FAIR

• Claudia Höhne, GSI Darmstadt
• CBM collaboration

• Outline
• physics case
• CBM experiment
• feasibility studies of key observables

supported by EU/FP6 HadronPhysics
2
Introduction

• milestone in mapping the QCD phase diagram would
  be the (unambiguous) discovery of either the
  critical point or the 1st order phase transition
• top SPS, RHIC, LHC
• high T, low mB region
• most probably crossover
• high mB region !
• onset of deconfinement?
• 1st order phase transition?
• critical point?
• high baryon density!
• lower SPS, AGS
• limited in observables,
• statistics
• ? SIS 300 _at_ FAIR
• 2nd generation experiment! ? charm,
  dileptons, fluctuations, correlations

3
Dense baryonic matter

• baryon density in central cell (AuAu, b0 fm)
  in transport calculations HSD (mean field,
  hadrons resonances strings), QGSM similar
  results
• enormous energy and baryon densities reached! (e
  gt ecrit)

CBM physics group, C. Fuchs priv. com.
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Phase diagram

• UrQMD calculation of T, mB as function of
  reaction time
• (open symbols nonequilibrium,
• full symbols appr. pressure equilibrium)
• phase border crossed already at rather low
  energies
• (see also results from 3-fluid hydrodynamics)
• critical point in reach?

CBM energy range 15 - 35 AGeV for AuAu
Bratkovskaya et al., PRC 69 (2004) 054907
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Physics of CBM
rare probes ? high interaction rates!
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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
• not necessarily fixed layout!
• more like facility

STS
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open charm production

• D0 ? K-p (ct 124 mm), minimum bias AuAu
  collisions at 25 AGeV
• ltD0gt 4 10-5
• 50 mm secondary vertex resolution
• proton identification via TOF
• even better signal for
• D ? K-pp
• (3-particle 2nd vertex)

see poster of I. Vassiliev (HK21.40)
Mishra et al ., Phys. Rev. C 69, 015202 (2004)
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Dileptons

• dileptons are penetrating probes!
• modifications in hot and dense matter expected
  
• see CERES, NA50, NA60, HADES

best way to measure? ee- ? mm-
Rapp, Wambach, Adv. Nucl. Phys. 25 (2000) 1,
hep-ph/9909229
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dileptons - electrons

• low-mass vector mesons develop sophisticated
  cut strategy
• J/y cut on pt (1GeV) seems sufficient
• so far no track reconstruction, PID included

see poster of T. Galatyuk (HK 21.10)
central AuAu, 25 AGeV
J/??ee-
pt gt100 MeV
?
f
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dileptons - muons

• study alternative CBM setup with active muon
  absorbers (Fe C detector layers)
• minimum bias AuAu, 25 AGeV
• low efficiency for soft muons
• challenging muon detectors

J/??µµ-
?
f
?
see poster of A. Kiseleva (HK 21.43)
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dynamical fluctuations

• UrQMD central AuAu collisions at 25 AGeV, no
  track reconstruction

4 ? acceptance identified particles
K/ ? 3.2 ? 0.3 2.6 ? 0.6
p/ ? -5.3 ? 0.07 -5.9 ? 0.1
see poster of D. Kresan (HK 21.42)

• resonance contribution?
• little influence of limited detector acceptance
• measurement feasible if dyn. fluctuations gt 2

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CBM status and outlook

• FAIR recently approved by german cabinet
• CBM offers a very interesting physics program
• detector development under way
• increasingly realistic feasibility studies are
  performed
• open charm measurement well possible
• dilepton spectrum via dielectrons or dimuons?
• particle ratio fluctuations measurable down to
  2

talks at DPG F. Uhlig HK 13.3 J. Heuser HK
32.6 C. Steinle HK 32.7 posters at DPG T.
Galatyuk HK 21.10 I. Vassiliev HK 21.40 D.
Kresan HK 21.42 A. Kiseleva HK 21.43 M. Hoppe
HK 21.64 E. Cordier HK 21.65 S. Amar-Youcefi HK
21.79
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CBM collaboration
CBM Collaboration 40 institutions, gt 350
Members
Croatia RBI, Zagreb China Wuhan Univ. Hefei
Univ. Cyprus Nikosia Univ.   Czech
Republic CAS, Rez Techn. Univ. Prague France
IReS Strasbourg Hungaria KFKI Budapest Eötvös
Univ. Budapest India VECC Kolkata    
Romania NIPNE Bucharest Russia IHEP
Protvino INR Troitzk ITEP Moscow KRI, St.
Petersburg Kurchatov Inst., Moscow LHE, JINR
Dubna LPP, JINR Dubna LIT, JINR Dubna MEPHI
Moscow Obninsk State Univ. PNPI Gatchina SINP,
Moscow State Univ. St. Petersburg Polytec.
U. Ukraine Shevshenko Univ. , Kiev
Korea Korea Univ. Seoul Pusan National
Univ. Norway Univ. Bergen Germany Univ.
Heidelberg, Phys. Inst. Univ. HD, Kirchhoff Inst.
Univ. Frankfurt Univ. Kaiserslautern Univ.
Mannheim Univ. Münster FZ Rossendorf GSI
Darmstadt Poland Krakow Univ. Warsaw
Univ. Silesia Univ. Katowice   Portugal LIP
Coimbra
supported by EU/FP6 HadronPhysics, INTAS
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multiplicities

• AuAu, 25 AGeV

Particle Ncentral Nmbias
? 38 15.2
? 1.28 0.512
?0 28 9.2
J/y 1.92 10-5 7.7 10-6
D0 4 10-5
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EOS in dense baryonic matter

• strong indications for soft EOS below 3r0 from
  SIS (subthreshold K, flow)
• ... and at 8r0 with e gt ecrit ??
• consequences?
• ? dileptons, charm!?

C. Fuchs, priv. com.
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Feasibility studies

• study feasibility of measurement of key
  observables by means of full scale simulations of
  the CBM detector and event reconstruction
• tracking efficiency and momentum resolution in
  STS (2 MAPS, 1 hybrid pixel, 4 strip detectors)