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


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.]


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


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!


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


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) ]


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- ↔ +-


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


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)


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%


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


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


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]


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)

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

Documents

au slide

fair claudia hhne

kresan hk

galatyuk hk

kiseleva hk

au collisions

mev slide

steinle hk