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THE MUON DETECTION SYSTEM FOR THE CBM EXPERIMENT AT FAIR/GSI

A. Kiseleva

Helmholtz International Summer SchoolDense Matter In Heavy Ion Collisions and Astrophysics (DM2008)

July 14 – 26, 2008

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Outline

FAIR project CBM experiment:

– setup– observables

The muon detection system for CBM– layout– feasibility studies for:

ρ, ω, φ J/ψ

Conclusions and next steps

3

FAIR: the international Facility for Antiproton and Ion Research

GSI: Gesellschaft für Schwerionenforschung

GSI/FAIR

4

FAIR: the international Facility for Antiproton and Ion Research

storage and cooler rings

• beams of rare isotopes• e – A Collider

• 1011 stored and cooled antiprotons

0.8 - 14.5 GeV

primary beams

• 5∙1011/s; 1.5-2 GeV/u; 238U28+

• factor 100-1000 increased intensity• 4x1013/s 90 GeV protons• 1010/s 238U 35 GeV/u (Ni 45 GeV/u)

secondary beams

• rare isotopes 1.5 - 2 GeV/u; factor 10 000 increased intensity • antiprotons 3(0) - 30 GeV

accelerator technical challenges

• rapidly cycling superconducting magnets• high energy electron cooling• dynamical vacuum, beam losses

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Research programs at FAIR

Rare isotope beams: nuclear structure and nuclear astrophysicsnuclear structure far off stabilitynucleosynthesis in stars and supernovae

Beams of antiprotons: hadron physicsquark-confinement potentialsearch for gluonic matter and hybridshypernuclei

Nucleus-nucleus collisions: compressed baryonic matter baryonic matter at highest densities (neutron stars) phase transitions and critical endpointin-medium properties of hadrons

Short-pulse heavy ion beams: plasma physicsmatter at high pressure, densities, and temperaturefundamentals of nuclear fusion

Atomic physics, FLAIR, and applied researchhighly charged atomslow energy antiprotonsradiobiology

Accelerator physicshigh intensive heavy ion beamsdynamical vacuumrapidly cycling superconducting magnetshigh energy electron cooling

CBM experiment

Nucleus-nucleus collisions: compressed baryonic matter baryonic matter at highest densities (neutron stars) phase transitions and critical endpoint in-medium properties of hadrons

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Physics case

• crossover transition from partonic to hadronic matter at small B and high T

• critical endpoint in intermediate range of the phase diagram • first order deconfinement phase transition at high B but moderate T

hea

t

compression

Predictions from lattice QCD:

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CBM physics topics and abservables

In-medium modifications of hadronsIn-medium modifications of hadrons • onset of chiral symmetry restoration at high densities onset of chiral symmetry restoration at high densities ρρBB

• measure: measure: ρρ, , ωω, , φφ → e → e++ee-- / / μμ++μμ--

• open charm (D mesons) open charm (D mesons)

Strangeness in matter (strange matter?)Strangeness in matter (strange matter?)• enhanced strangeness production ?enhanced strangeness production ?• measure: K, measure: K, ΛΛ, , ΣΣ, , ΞΞ. . ΩΩ

Indications for deconfinement at high Indications for deconfinement at high ρρBB • anomalous charmonium suppression ?anomalous charmonium suppression ?• measure: J/measure: J/ψψ, , ψψ' ' → e→ e++ee-- / / μμ++μμ--,, D D00 → K → Kππ, D, D±± →→ K Kππππ • softening of EOS softening of EOS • measure flow excitation function measure flow excitation function

Critical point Critical point • event-by-event fluctuations

Color superconductivityColor superconductivity• precursor effects ?precursor effects ?

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Dilepton sources in heavy-ion collisions

Searching for the onset of deconfinement

Investigation of dense baryonic matter using penetrating probes

shift

? broadening

? melting

? ...

?

In-medium modifications of low-mass vector mesons:

J/ψ dissociation in the QGP

? sequential melting of

ψ’ and J/ψ

? modifications of pt

distribution ? collective flow of

charmonium

? …

?

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10-1 100 101 102 103 10410-6

10-4

10-2

100

102

104

AGS SPS RHIC HSD ' 99

__

D(c)

J/D(c)

KK+

+

Mul

tipl

icit

y

Au+Au (central)

Energy [A GeV]

Yields for central Au+Au at 25 AGeV

J/ψ(3095 MeV)

ρ0

(770 MeV)

ω(782 MeV)

φ(1020 MeV)

1.95×10-5 23 38 1.28

6%4.6×10-

5 9×10-5 2.9×10-

4

~1×10-6 ~1×10-

3

3.4×10-3

3.7×10-

4

multiplicity

branching ratio (μμ)

yield per event

φφJ/J/ψψ

ππ++

CBM

pion-to-charmonium ratio ~

109 !

W. Cassing, E. Bratkovskaya, A. SibirtsevNucl. Phys. A 691 (2001) 745

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Experimental requirements

high statisticshigh statistics large signal-to-background ratiolarge signal-to-background ratio good mass resolutiongood mass resolution large acceptance large acceptance high reconstruction efficiencyhigh reconstruction efficiency

160 p400 -

400 +

44 K+

13 K-

Central Au+Au collision Central Au+Au collision at 25 at 25 AAGeVGeV

(UrQMD + GEANT3)(UrQMD + GEANT3)

• up to 107 Au+Au reactions/sec (beam intensities up to 109 ions/s with 1 % interaction target)

• determination of (displaced) vertices with high resolution ( 50 m)

• identification of leptons and hadrons

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CBM for dimuon measurements

STSSTS MuChMuCh TRDTRD ToFToF

STSSTS track, vertex and track, vertex and momentum reconstruction momentum reconstruction

MuChMuCh muon identification muon identification

TRDTRD global tracking global tracking

RPC-ToFRPC-ToF time-of-flight measurement time-of-flight measurement

Measurements:charmonium – standard MuCh (13.5λI)

low-massvector mesons – compact MuCh (7.5λI)

GEANT3 model

STS

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Muon detector segmentation

max pad 44.8 44.8 mm2

space resolution: x – 12.8 mm, y – 12.8 mm

min pad 1.4 2.8 mm2

space resolution: x – 400 μm, y – 800 μm

Mikhail Ryzhinskiy, Saint-Petersburg State Polytechnical University

5% occupancy

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Simulations

Signals: multiplicities from Hadron-String Dynamics (HSD)

– ρ, ω, φ, η and ηDalitz

– J/ψ, Ψ'

Background: Ultrarelativistic Quantum Molecular Dynamics (UrQMD)

– central Au+Au at 25 AGeV

www.th.physik.uni-frankfurt.de/~brat/hsd.html

www.th.physik.uni-frankfurt.de/~urqmd/

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Muon reconstruction

J/ψμ+

μ-

S. Gorbunov, Kirchhoff Inst. f. Physik, Universität HeidelbergI. Kisel, GSI

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Results

Signal-to- Efficiency MassSignal-to- Efficiency Mass

Background (%) resolution Background (%) resolution

(S/B) ratio (MeV)(S/B) ratio (MeV)

ω ω 0.09 0.09 2 10 2 10

φφ 0.03 0.03 4 12 4 12

J/ψJ/ψ 18 13 21 18 13 21

Ψ'Ψ' 0.8 16 27 0.8 16 27

Central Au+Au collisions at 25 AGeV

signals

J/ψ

Ψ'

signals

J/ψ

Ψ'

background

signals

ρ

ω

φ

η

ηDalitz

signals

ρ

ω

φ

η

ηDalitz

background

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Analysis of background composition

compact MuCh (7.5λI) standard MuCh (13.5λI)

Masse of particles:μ – 106 MeV, π – 140 MeV, Κ – 498 MeV, p – 938 MeV

Central Au+Au collisions at 25 AGeV

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Background rejection via mass determination

m2 =

β =

γ =

m2 = P2 ( - 1)

Lc × t

√1 – β2

1

(β × γ)2

P2

β2

1

(L, t) → (L, t) → ββ

ToF

m2 (GeV2/c4)

P (

GeV

/c)

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Improved results with pIDToF

610-3

510-4

without ToF with ToF

Central Au+Au collisions at 25 AGeV

compact MuCh (7.5λI)

S/B ratio eff.%

0.09 2.0

0.03 4.1

S/B ratio eff.%

0.17 1.5

0.06 3.0

ω

φ

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Results for different collision systems

central Au+Au central Au+Au @ 25 @ 25 AAGeVGeV

central Au+Au @ central Au+Au @

8 8 AAGeVGeV

central central p+C p+C

@ 30 @ 30 AAGeVGeV

ωωToF pIDToF pID J/J/ψψ ωωToF pIDToF pID J/J/ψψ ωω J/J/ψψ

S/BS/B 0.170.17 1818 0.14 0.14 (0.09)*(0.09)*

–– 1111 147147

εε, , %%

1.51.5 1313 0.8 0.8 (1.2)*(1.2)* –– 44 2323

* in order to increase the acceptance of reconstructed ω we can use different type of tracks

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Study of possible detector solutions

Detector requirements:Detector requirements: high rate capability (up to 1 MHz/cmhigh rate capability (up to 1 MHz/cm22) ) high granularity (up to 1 hit/cmhigh granularity (up to 1 hit/cm22ss-1 -1 for central Au+Au for central Au+Au

collisions)collisions) position resolution < 300 position resolution < 300 μμmm

Detector options:Detector options: GEMGEM

((Gas Electron Multiplier))

MicromegasMicromegas ((Micro Mesh Gaseous Detector)

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Detector prototypes: GEMs

LHE JINR Dubna

PNPI St. PetersburgPNPI St. Petersburg

VECC KolkataVECC Kolkata

Support structure

PadsPads

FastenersFasteners

SpacerSpacer

PCBPCB Readout electronicsReadout electronics

ArgonArgon

GEM foilsGEM foils

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Conclusions

Promising results for low-mass Promising results for low-mass vector mesons vector mesons

Good result for J/Good result for J/ψψ

ψψ' identification seems possible ' identification seems possible

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Next steps

Implementation of muon triggerImplementation of muon trigger Realistic detector response:Realistic detector response:

– clustering clustering – realistic detector inefficiencyrealistic detector inefficiency

Muon system optimization:Muon system optimization:– necessary number of detector layersnecessary number of detector layers– additional absorber in STSadditional absorber in STS– detector resolution studydetector resolution study

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Thank youfor your attention!

China

Croatia

Cyprus

Czech Republic

France

Germany

Hungaria

India

Korea

Norway

Poland

Portugal

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Russia

Ukraine

China

Croatia

Cyprus

Czech Republic

France

Germany

Hungaria

India

Korea

Norway

Poland

Portugal

Romania

Russia

Ukraine52 institutions, more than 400 members (May 2008)

www.gsi.de/fair/experiments/CBM/index.html

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Signal acceptance

J/ψ→μ+μ-

ρ→μ+μ-

Pluto

Pluto

STS

STS

1m Fe

1m Fe

Central Au+Au collisions at 25 AGeV

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Signal parameters: J/ψ

J/ψ

Bg

Bg J/ψ

2

(central Au+Au at 25AGeV)

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Signal parameters: ρ0

ρ0

Bg

Bg ρ0

2

(central Au+Au at 25AGeV)

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Hard-soft pairsρ0→μ+μ-

— hard-hard (h-h) pairs

— hard-soft (h-s) pairs

— h-h + h-s

μhard

μsoft

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Digitization algorithm

primary electrons

sec. electron

s

Advanced digitization and cluster finding in MuCh, M. Ryzhinskiy