The CBM experiment - exploring the QCD phase diagram at high net baryon densities - Claudia Höhne, GSI Darmstadt CBM collaboration The CBM experiment physics.

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 - Claudia Höhne, GSI Darmstadt CBM collaboration The CBM experiment physics.

Documents

high density

agev slide

high baryon

agev central au

high track density

high hit densities

agev beam energy slide

preparation slide