the cbm experiment - exploring the qcd phase diagram at high net baryon densities -

The CBM experiment- exploring the QCD phase diagram at high net baryon densities -

Claudia Höhne, GSI Darmstadt

CBM collaboration

The CBM experiment

• physics case, observables

• detector layout

• feasibility studies and R&D of detector components

2 Claudia Höhne DPG Frühjahrstagung, Gießen, März 2007

Physics caseCompressed Baryonic Matter @ FAIR – high B, 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 starting in 2015

• physics program complementary to ALICE

• measurement of charm production at threshold A.

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High density matter

• high baryon and energy densities created in central Au+Au collisions

• remarkable agreement between different models

• max. net baryon densities from 5 - 40 AGeV ~ 1 - 2 fm-3 ~ (6 – 12) 0

(net baryon density = 1 fm-3 ~60)

• max. excitation energy densities from 5 - 40 AGeV ~ (0.8 – 6) GeV/fm3

(* = – mN, total energy density)

net baryon density excitation energy density

[CBM physics group, J. Randrup priv. com.]


Physics topics and Observables

Onset of chiral symmetry restoration at high B

• in-medium modifications of hadrons (,, e+e-(μ+μ-), D)

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

The equation-of-state at high B

• collective flow of hadrons• particle production at threshold energies (open charm)

QCD critical endpoint• excitation function of event-by-event fluctuations (K/π,...)

• mostly new measurements• CBM Physics Book (theory) in preparation


The CBM experiment• tracking, momentum determination, vertex reconstruction: radiation hard silicon pixel/strip detectors (STS) in a magnetic dipole field

• hadron ID: TOF (& RICH)• photons, 0, : ECAL

• electron ID: RICH & TRD suppression 104

• PSD for event characterization• high speed DAQ and trigger → rare probes!

• muon ID: absorber + detector layer sandwich move out absorbers for hadron runs

MVD + STS

aim: optimize setup to include both, electron and muon ID (not necessarily simultaneously)


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


STS tracking

Challenge: high track density 600 charged particles in 25o

Task

• track reconstruction:

0.1 GeV/c < p 10-12 GeV/c

p/p ~ 1% (p=1 GeV/c)

• primary and secondary vertex reconstruction (resolution 50 m)

• V0 track pattern recognition

D+ → ++K- (c = 317 m)

D0 → K-+ (c = 124 m)

silicon pixel

and strip detectors


Open charm production• D0 → K-+ (c= 124 m)

• <D0> = 4∙ 10-5

• first MAPS detector at 10cm

• ~53 m secondary vertex resolution

• proton identification with TOF

1.6 107 central Au+Au collisions, 25 AGeV

central Au+Au, 25 AGeV


4"280 µm

Microstrip Sensors Tracking Stations

layout studies

module design

J. Heuser HK 22.2

Silicon Strip Sensor R&D


Fast self-triggered readout electronics

NXYTER chip produced; DETNI − GSI

test system under construction

micro-strip sensor

K. Solvag HK 34.8


Dileptons - electrons

• low-mass vector mesons: try to reject large physical background (-conversion, Dalitz decays) by high performance tracking

• J/: cut on pt (1.2 GeV/c)

• high purity of electron identification needed! (-suppr. > 104 achievable)

S/B=1.7

eff. 12%

J/ mesonlow-mass vector mesons

S/B = 0.2eff. 7.5%

T. Galatyuk HK 19.3

100k events = 10s of beam time

central Au+Au, 25 AGeV

1010 events


Dileptons - muons

• low efficiency for soft muons → investigate momentum dependent identification

• phantastic J/(pt > 1 GeV/c), even ' should be accessible

• however: high hit densities in detectors!

J/ meson

(add 1m Fe)

low-mass vector mesons (1.25 m Fe)

S/B = 0.4eff. 1.3% eff. 20%

A. Kiseleva HK 19.4central Au+Au, 25 AGeV

4∙108 events


First test beam data → hit density?

without Pb converter

with Pb converter (1.5 cm ~ 3X0)

• hit densities after absorbers? (reliability of simulation?)

• first results from test beam (6 GeV/c) at CERN, PS on high granularity gas detectors (ALICE prototypes):

→ increase hit density in GEANT 3 appr. by factor 2

ADC counts


CBM collaboration

Russia:IHEP ProtvinoINR TroitzkITEP MoscowKRI, St. Petersburg

China:CCNU WuhanUSTC Hefei

Croatia: RBI, Zagreb

Portugal: LIP Coimbra

Romania: NIPNE Bucharest

Poland:Krakow Univ.Warsaw Univ.Silesia Univ. KatowiceNucl. Phys. Inst. Krakow

LIT, JINR DubnaMEPHI MoscowObninsk State Univ.PNPI GatchinaSINP, Moscow State Univ. St. Petersburg Polytec. U.

Ukraine: Shevchenko Univ. , Kiev

Cyprus: Nikosia Univ.

Univ. Mannheim Univ. MünsterFZ RossendorfGSI Darmstadt

Czech Republic:CAS, RezTechn. Univ. Prague

France: IPHC Strasbourg

Germany: Univ. Heidelberg, Phys. Inst.Univ. HD, Kirchhoff Inst. Univ. FrankfurtUniv. Kaiserslautern

Hungaria:KFKI BudapestEötvös Univ. Budapest

India:VECC KolkataSAHA KolkataIOP BhubaneswarUniv. ChandigarhUniv. VaranasiIlT Kharagpur

Korea:Korea Univ. SeoulPusan National Univ.

Norway:Univ. Bergen

Kurchatov Inst. MoscowLHE, JINR DubnaLPP, JINR Dubna

46 institutions

> 400 members

Strasbourg, September 2006

CBM related talks:

M. Klein-Bösing HK 16.8 T. Galatyuk HK 19.3A. Kiseleva HK 19.4 J. Heuser HK 22.2K. Solvag HK 34.8 D. Gonzalez-Diaz HK 47.4S. Gorbunov HK 53.1 C. Steinle HK 53.4

CBM related poster:

C. Müntz HK 49.23

the cbm experiment - exploring the qcd phase diagram at high net baryon densities -

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