the compressed baryonic matter (cbm) experiment at fair claudia höhne, gsi darmstadt cbm...

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 Claudia Höhne DPG Frühjahrstagung, München, März 2006

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 B region –

most probably crossover

• high B region !

onset of deconfinement?

1st order phase transition?

critical point?

high baryon density!

• lower SPS, AGS:

limited in observables,

statistics

→ SIS 300 @ FAIR

2nd generation experiment! → charm, dileptons, fluctuations, correlations

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Dense baryonic matter

• baryon density in central cell (Au+Au, b=0 fm) in transport calculations HSD (mean field, hadrons + resonances + strings), QGSM similar results

• enormous energy and baryon densities reached! ( > crit)

[CBM physics group, C. Fuchs priv. com.]

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Phase diagram

[Bratkovskaya et al., PRC 69 (2004) 054907]

• UrQMD calculation of T, B 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 Au+Au

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Physics of CBM

physics topics

deconfinement at high B ?

softening of EOS ?

order of phase transition ?

Critical point ?

in-medium properties of hadrons

onset of chiral symmetry restoration at high B

observables

strangeness production: K,

charm production: J/, D

flow excitation function

event-by-event fluctuations

e+e-

open charm

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) suppression 104

• hadron ID: TOF (& RICH)

• photons, 0, : ECAL

• high speed DAQ and trigger

• not necessarily fixed layout!

• more like „facility“

STS

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open charm production• D0 → K-+ (c= 124 m), minimum bias Au+Au collisions at 25 AGeV

• <D0> = 4∙ 10-5

• ~50 m secondary vertex resolution

• proton identification via TOF

• even better signal for D+ → K-++

(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

[Rapp, Wambach, Adv. Nucl. Phys. 25 (2000) 1, hep-ph/9909229]

• dileptons are penetrating probes!

• modifications in hot and dense matter expected –

see CERES, NA50, NA60, HADES

best way to measure? e+e- ↔ +-

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dileptons - electrons• low-mass vector mesons: develop sophisticated cut strategy

• J/: cut on pt (1GeV) seems sufficient

• so far no track reconstruction, PID included

see poster of T. Galatyuk (HK 21.10)

J/ψ→e+e-

central Au+Au, 25 AGeV

pt >100 MeV

φω

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dileptons - muons

• study alternative CBM setup with active muon absorbers (Fe + C + detector layers)

• minimum bias Au+Au, 25 AGeV

• low efficiency for soft muons

• challenging muon detectors

J/ψ→μ+μ-

ρ φωsee poster of A. Kiseleva (HK 21.43)

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dynamical fluctuations

4 acceptance identified

particles

K/ 3.2 0.3 2.6 0.6

p/ -5.3 0.07 -5.9 0.1

datamixed events

2 2dyn data mixed

• UrQMD: central Au+Au collisions at 25 AGeV, no track reconstruction

see poster of D. Kresan (HK 21.42)

• resonance contribution?

• little influence of limited detector acceptance

• measurement feasible if dyn. fluctuations > 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 collaborationCBM Collaboration : 40 institutions, > 350 Members

Croatia: RBI, Zagreb

China:Wuhan Univ.Hefei Univ.

Cyprus: Nikosia Univ.  Czech Republic:CAS, RezTechn. Univ. Prague

France: IReS Strasbourg

Hungaria:KFKI BudapestEötvös Univ. Budapest

India:VECC Kolkata

Romania: NIPNE Bucharest

Russia:IHEP ProtvinoINR TroitzkITEP MoscowKRI, St. PetersburgKurchatov Inst., MoscowLHE, JINR DubnaLPP, JINR DubnaLIT, JINR DubnaMEPHI MoscowObninsk State Univ.PNPI GatchinaSINP, Moscow State Univ. St. Petersburg Polytec. U.

Ukraine: Shevshenko Univ. , Kiev

Korea:Korea Univ. SeoulPusan National Univ.

Norway:Univ. Bergen

Germany: Univ. Heidelberg, Phys. Inst.Univ. HD, Kirchhoff Inst. Univ. FrankfurtUniv. KaiserslauternUniv. Mannheim Univ. MünsterFZ RossendorfGSI Darmstadt

Poland:Krakow Univ.Warsaw Univ.Silesia Univ. Katowice Portugal: LIP Coimbra

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multiplicities

• Au+Au, 25 AGeV

Particle Ncentral Nmbias

38 15.2

1.28 0.512

0 28 9.2

J/ 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 ~ 30 from SIS (subthreshold K+, flow)

• ... and at 80 with > crit ??

• consequences? → dileptons, charm!?

[C. Fuchs, priv. com.]

[W. Weise, Proc. Hirschegg 2001]

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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)