Muon simulations

16 October 2008 1 12th CBM Collaboration meeting Oct. 13-18 2008, JINR Dubna

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Muon simulations

Anna Kiseleva

16 October 2008 12th CBM Collaboration meeting Oct.

13-18 2008, JINR Dubna

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Outline• Muon simulations for different collision systems:

• SIS 300

• SIS 100

• Muon system optimizations:• material of pipe shielding

• thickness of first absorber

• alternative solutions of muon system

• Additional electrons from absorber:• comparison of different simulation tools

• enhanced "noise" from secondary electrons

• Conclusions• Next steps



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Simulations• cbmroot release v.APR08• signals: multiplicities from HSD, Pluto generator

• ω, J/ψ

• background: UrQMD central events• Au+Au at 15, 25 and 35 AGeV

• Au+Au at 8 AGeV

• p+C at 30 GeV

• muon magnet• standard STS• standard MuCh• MuCh hit producer without clusters• L1 (STS) and L1/Lit (MuCh) tracking



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C B MStandard Muon Chambers (MuCh) system

low-mass vector meson measurements(compact setup)

≡ 7.5 λI ≡ 13.5 λI

Fe

20 20 2

0 30

35 1

00 cm

shielding

5%occupancyfor central

Au+Au collisionsat 25 AGeV

w/o shielding

Total number

of channels:

480768

min pad 1.42.8 mm2

max pad 44.844.8 mm2



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C B MAu+Au at 25 AGeV*

Signal-to- Efficiency Mass

Background (%) resolution

(S/B) ratio (MeV)

ω 0.09 2 10

φ 0.03 4 12

J/ψ 18 13 21

Ψ' 0.8 16 27

signals

J/ψ

Ψ'

background

signals

ρ

ω

φ

η

ηDalitz

background

* 10th CBM Collaboration Meeting



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Lit tracking Andrey Lebedev "Track reconstruction in MUCH"

Standard MuCh: 6 Fe absorbers (225 cm)

18 detector stations

Compact MuCh: 5 Fe absorbers (125 cm)

10 detector stations

Events: URQMD central Au+Au at 25 AGeV

+5 mu+ and 5 mu- in each event

(p=1.5..10 GeV/c for compact and p=2.5..25 GeV/c for standard)

Compact Standard

all 96.2% 97.5%

ref 97.1% 97.6%

prim 96.4% 97.5%

sec 89.2% 89.0%

muons 96.8% 97.5%

ghost 1.5% 0.21%

clone 0.0% 0.0%



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Tracking proceduresReconstructed background:

L1 Lit

L1 Lit

S/B 0.091 0.095

ε, % 1.7 1.9

Andrey Lebedev "Track reconstruction in MUCH"

ω→μ+μ- + central Au+Au collisions at 25 AGeV


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SIS 100

Au+Au at 8 AGeV

p+C at 30 GeV



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Compact muon system

Au+Au at 8 AGeV

min. 9 hits tracks min. 12 hits tracks

Pluto

ω in Au+Au collisions at 8 AGeV



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Results of L1 reconstruction

ω

min. 9 hits min. 12 hits

S/B 0.05* 0.1*

ε, % 1.65 0.95

Au+Au at 8 AGeV

* we can improve results, if we will have ToF pID in MuCh and/or make some simple modifications of CBM setup (see backup slides)



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J/ψ + central p+C collisionsω + central p+C collisions

1 ω→μ+μ- in 105 central events 4 J/ψ→μ+μ- in 109 central events


p+C at 30 GeV

ω J/ψ

S/B 11 147

ε, % 4.3 22.7

comparison of HSD and Pluto generated J/psi - see backup slides


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Muon system optimization



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Material of pipe shieldingpa

rtic

les/

(eve

nt×

cm2)

part

icle

s/(e

vent

×cm

2)

1 2 3

4 5― Fe

― W

― Pb + Fe

central Au+Au

collisions at 25 AGeV


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Thickness of first absorber



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with pipeshielding

with pipeshielding

Motivation: decrease hit density in first detector layers



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Particle absorption

central Au+Au collisions at 25 AGeV



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C B MThickness of first absorber (Fe)

10 cm 100 cm

10 cm Fe

20 cm Fe

30 cm Fe

40 cm Fe



≥4STS+3MuCh

4

ghosts !



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Alternative muon systems

40 20 20 20 25

30 20 20 20 35

20 20 20 30 35

10 20 30 30 35

central Au+Au collisions at 25 AGeV 10 cm Fe

20 cm Fe

30 cm Fe

40 cm Fe



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MuCh 25 30 40 40

25 30 40

40

Nchannels 439 296 → 272 384



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Comparison


MuCh

20 20 20 30 35

MuCh

25 30 40 40

S/B 0.095 0.094

ε, % 1.9 1.8

― MuCh 20 20 20 30 35

― MuCh 25 30 40 40


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Additional electrons from absorber



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C B MParticle rate in first MuCh detector

TGEANT3: hadronic processTGEANT4: QGSP_BERT_EMVTFluka



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C B MParticle statistics (per event): 20 cm Fe

particles: GEANT3 GEANT4 Fluka

all 836 1001 1141

primary 106 105 105

secondary: 730 896 1037

e 521 607 705

p 91 121 139

π 98 159 174




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particles: GEANT3 GEANT4 Fluka

all 100 % + 23 % + 42 %

primary 100 % + 16.5 % + 33.8 %

secondary: 100 % + 33 % + 52.8 %

e 100 % + 62 % + 77.6 %

p 100 % + 23 % + 42 %

π 100 % + 16.5 % + 33.8 %

Particle statistics (per event): 20 cm Fe central Au+Au collisions

at 25 AGeV



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Problems• TFluka is unstable in cbmroot

• Present setup of TGEANT4 doesn't include muon production in thick material

• Is production of secondary particles in absorber material correctly described?



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C B MModeling additional electron hits

e

1. Create true hit (X0, Y0)2. If e, create new point (X0+∆X,

Y0+∆Y)3. Create noise hit (Xnoise, Ynoise)4. Possibility to create more then 1

noise hit from 1 true e



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Statistics (per event)

standard 1e 2e 3e 4e 5e 10e

MC points

2991

hits 2910 4161 5411 6660 7909 9158 15408


?



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Horizontal hit distribution

MC points

― standard hitsadditional e:

― +1

― +2

― +5

― +10




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Invariant mass spectraω→μ+μ- + central Au+Au collisions at 25 AGeV



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Results of Lit reconstruction

standard hits

1e 2e 3e

S/B 0.095 0.090 0.11 0.076

ε, % 1.92 1.58 1.575 1.4




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Background

+1e +2e +3e




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Conclusions• Simulation tools have been developed to design and

optimize CBM muon detection system.

• The present muon detector design is tested for different collision systems and beam energies (incl. SIS100).

• Simulations with enhanced yield of secondary electrons have been started. Track reconstruction efficiency decrease slightly with increasing number of secondary electrons up to a factor of 3 which corresponds to an increase of total hit density by more than a factor of 2. Simulations with higher hit densities are in progress.



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Next steps• Implementation of:

• realistic detector description • different type of the detectors

• inefficiency of the detectors

• muon trigger

• additional secondary electrons with correlated hits in detectors

• Muon system optimizations:• number of sensitive layers

• thickness of absorbers

• optimization tacking into account costs

• Test of possible solutions of muon system using LMVM and charmonium simulations


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Thank you for your attention!


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Backup slides



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ToF(80 ps)

Muon system with ToFm2 =

β =

γ =

m2 = P2 ( - 1)

Lc × t

√1 – β2

1

(β × γ)2

P2

β2

1

Au+Au at 8 AGeV



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m2 vs. Preco

signal μ background

9 hits

12 hits

15 hits

9, 12 and 15 hits tracks



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Results after ToF pID

ω

min. 9 hits min. 12 hits

S/B 0.05→0.09 0.1→0.14

ε, % 1.65→1.2 0.95→0.8

Au+Au at 8 AGeV


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Possible modifications for increasing of signal

acceptance

Au+Au at 8 AGeV



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1. Decreasing magnet fieldmagnet field: 100% 50% magnet field: 100% 50%

+ 12% μω

+ 22% ω

Au+Au at 8 AGeV



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C B M2. Decreasing the thickness of the absorbers

Au+Au at 8 AGeV



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C B MJ/ψ in p+C @ 30 GeV: Pluto and HSD

HSD Pluto

Pluto

HSD

p+C at 30 GeV



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Pluto HSD

S/B 147 115

ε, % 22.7 13.3

p+C at 30 GeV



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Reconstructed J/ψ

Pluto

HSD

p+C at 30 GeV



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C B MComparison of ideal with realistic detector resolution

beam energies

15AGeV 25AGeV 35AGeV

S/B 0.08 0.07 0.07

ε, % 2.4 3.6 4.7

beam energy

── 15 AGeV

── 25 AGeV

── 35 AGeV

σ =100 μm

Lit

S/B 0.095

ε, % 1.9

ω→μ+μ- + central Au+Au collisions

segmentation

Documents

Muon simulations