Muon simulationsMuon simulations

Anna Kiseleva

OutlineOutline

• Muon system 2006

• New Muon Chamber system (MuCh)

• Track finding und selection

• Results for low-mass vector mesons

• J/ψ simulations

• Detector resolution study: preliminary results

• Conclusions and next steps

• Muon system 2006

• New Muon Chamber system (MuCh)

• Track finding und selection

• Results for low-mass vector mesons

• J/ψ simulations

• Detector resolution study: preliminary results

• Conclusions and next steps

MuCh system 2006MuCh system 2006

5 10 20 30

120 cm

150 cm 10 cm

W Fe C

0 cm

551cm

1. Outside of the magnet2. Detector in front of the system3. First thin absorber4. Thick last absorber5. 10 cm gap 6. Distance – 5.5 m

ProblemsProblems

● 50 KeV E-cutoff

ω at 25 AGeV:S/B = 8×10-2

efficiency = 4.4%too many μ from weak decays!

MAPS?

MuCh at 25 AGeV STS for MuCh

Track reconstruction

0 12 3 4 5 6

ProblemsProblems

ω at 25 AGeV:S/B = 8×10-2

efficiency = 4.4%too many μ from weak decays!

Track reconstruction

π

μ

ModificationsModifications

no MAPS!

STS for MuCh

More compact MuCh!More compact MuCh!

0 1 2 3 4 5 6

ω at 25 AGeV: old new S/B 8×10-2 8×10-2

efficiency 4.4% 3.6%

5.7˚(0.1 rad)3.0˚

ω at 15 AGeV: MAPS no MAPS S/B 8×10-2 7×10-2

efficiency 2.4% 2.2%

Increasing of the pipe holeIncreasing of the pipe hole

MuCh detector 2007MuCh detector 2007

Fe Fe Fe Fe Fe

20 20 2

0 30

35 cm

102.5 cm0 cm5 cm

260cm

1. Fist absorber inside of the magnet2. Last STS as a first detector3. First thick absorber4. 5 cm gap 5. Distance – 2.6 m (instead of 5.5 m)

Max rate of particlesMax rate of particles

Energy of beam

● 15 AGeV

● 25 AGeV

● 35 AGeV

0 1 2 3 4 5

STSSTS

Hybrid (750 μm) 30 cm 40 cm

Strip (400 μm) 50 cm

60 cm75 cm

100 cm

Hybrid (750 μm) 30 cm 40 cm

Strip (400 μm) 50 cm

60 cm75 cm

100 cm

CBM setupCBM setup

STS MuCh TRD ToF

SimulationsSimulations

• Signals (Pluto):

– ρ, ω, φ, η and ηDalitz

– J/ψ

• Background (UrQMD):– central Au+Au at 15, 25 and 35 AGeV

• Statistics:– 25 AGeV – 20k events

– 15 and 35 AGeV – 10k events

• Signals (Pluto):

– ρ, ω, φ, η and ηDalitz

– J/ψ

• Background (UrQMD):– central Au+Au at 15, 25 and 35 AGeV

• Statistics:– 25 AGeV – 20k events

– 15 and 35 AGeV – 10k events

Hit producersHit producers

• STS:– stsDigiVersion = "v05a"– 2 hybrid + 4 strip detectors

• MuCh:– 100 μm space resolution– 80 πsec time resolution

• ToF:– 0.2 cm space resolution– 80 πsec time resolution

• STS:– stsDigiVersion = "v05a"– 2 hybrid + 4 strip detectors

• MuCh:– 100 μm space resolution– 80 πsec time resolution

• ToF:– 0.2 cm space resolution– 80 πsec time resolution

TrackingTracking

• STS track reconstruction:– ≥ 4 STS hits

– χ2primary vertex cut

• MuCh track finder:– track selection – hard and soft

– χ2track

• ToF hit finder:– χ2

hit position

• STS track reconstruction:– ≥ 4 STS hits

– χ2primary vertex cut

• MuCh track finder:– track selection – hard and soft

– χ2track

• ToF hit finder:– χ2

hit position

CBMCBM

STS MuCh TRD ToF

Tacking into account ToF information

Tacking into account ToF information

PPToFToF = m = mμμ × × ββ × × γγ

ββ = , t = T = , t = TToF ToF – T– TMuChMuCh

γγ = =

LLc × tc × t

√√1 – 1 – ββ22

11

PPMuChMuCh – Kalman Filter track extrapolation – Kalman Filter track extrapolation

MuChMuChL

ToFToF

PToF vs. Plast MuChPToF vs. Plast MuCh

φ signal background

PToF vs. Plast MuCh: cutsPToF vs. Plast MuCh: cuts

φ signal background

1 – branch cut1 – branch cut

2 – cone cut2 – cone cut

ResultsResults

= 0.5= 0.2= 0.01= 0.2= 0.007

= 1.1= 2.2= 0.5= 0.2= 0.7

= 0.4= 0.2= 0.008= 0.1= 0.005

= 1.3= 2.6= 0.6= 0.2= 1.0

= 0.2= 0.05= 0.004= 0.05= 0.003

= 2.6= 5.2= 1.2= 0.3= 2.2

————— S/B ratio ———————————————————————————— S/B ratio ———————————————————————

Branch cutBranch cut Cone cutCone cut

————— Efficiency (%) —————————————————————————— Efficiency (%) —————————————————————

ωφηηDalitz

ρ

ωφηηDalitz

ρ

ωφηηDalitz

ρ

ωφηηDalitz

ρ

[0.2; 0.9] GeV/c2

[0.2; 0.3] GeV/c2

without cutswithout cuts

25 AGeV25 AGeV

Invariant mass spectrumInvariant mass spectrum

signals:

ρ

ω

φ

η

ηDalitz

— background

— background+signals

branch time cut

25 AGeV25 AGeV

Invariant mass spectrumInvariant mass spectrum

signals:

ρ

ω

φ

η

ηDalitz

— background

— background+signals

branch time cut

25 AGeV25 AGeV

Rapidity of reco ρ0 Rapidity of reco ρ0

need more statistics!

25 AGeV25 AGeV

Types of tracksTypes of tracks

soft

μ

μ

hard

mean ± 2σmean ± 2σ

— ρ signal— background— gauss fit

Cuts for the soft tracksCuts for the soft tracks

— ω signal— background— gauss fit

mean ± 2σmean ± 2σ

reconstructed on STS momentum

β parameter from timemeasurements

ββ = =LL

c × tc × t

25 AGeV25 AGeV

ωφηηDalitz

ρ

ωφηηDalitz

ρ

ωφηηDalitz

ρ

ωφηηDalitz

ρ

[0.2; 0.9] GeV/c2

[0.2; 0.3] GeV/c2

Results (h-s pairs)Results (h-s pairs)

= 0.15= 0.06= 0.003= 0.02= 0.001

= 1.2= 1.6= 0.8= 0.2= 0.8

= 0.02= 0.006= 0.0007= 0.009= 0.0003

= 2.2= 3.0= 1.4= 0.4= 1.6

————— S/B ratio ———————————————————————————— S/B ratio ———————————————————————

————— Efficiency (%) —————————————————————————— Efficiency (%) —————————————————————

without cutswithout cuts

hard μ: with branch time cutsoft μ: with momentum cutwithout time with timeinformation information

hard μ: with branch time cutsoft μ: with momentum cutwithout time with timeinformation information

= 0.09= 0.04= 0.002= 0.02= 0.0008

= 1.4= 1.8= 0.9= 0.3= 0.9

25 AGeV25 AGeV

Rapidity of reco ρ0 Rapidity of reco ρ0

— hard-hard (h-h) pairs

— hard-soft (h-s) pairs

— h-h + h-s2 times more statistics!

25 AGeV25 AGeV

Efficiency of ρ0RECO (h-h+h-s)Efficiency of ρ0RECO (h-h+h-s)

full

ptρ (GeV/c):

< 0.2

[0.2, 0.4]

[0.4, 0.6]

[0.6, 0.8]

[0.8, 1.0]

> 1.0

▼

▲

▲

25 AGeV25 AGeV

ResultsResults

0.15 0.40.06 0.20.003 0.0080.02 0.10.001 0.005

1.2 1.31.6 2.60.8 0.60.2 0.20.8 1.0

25 AGeV25 AGeV

h-s h-h

0.19 0.40.03 0.070.004 0.0080.04 0.050.002 0.003

1.0 1.01.0 1.40.7 0.40.3 0.060.8 0.4

15 AGeV15 AGeV

h-s h-h

0.14 0.40.05 0.10.002 0.0060.03 0.040.001 0.003

1.3 1.51.7 2.70.7 0.60.4 0.10.9 0.8

35 AGeV35 AGeV

h-s h-h

ωφηηDalitz

ρ

ωφηηDalitz

ρ

ωφηηDalitz

ρ

ωφηηDalitz

ρ

[0.2; 0.9] GeV/c2

[0.2; 0.3] GeV/c2

————— S/B ratio —————————————————————————————— S/B ratio —————————————————————————

————— Efficiency (%) ———————————————————————————— Efficiency (%) ———————————————————————

hard μ: with branch time cut soft μ: with momentum and time cut

Invariant mass spectraInvariant mass spectra

hard-hard pairs:

background + signals

35 AGeV

25 AGeV

15 AGeV

— background

J/ψ simulations: add 1m FeJ/ψ simulations: add 1m Fe

Fe Fe Fe Fe Fe Fe

20 20 2

0 30

35 100 cm

central Au+Au collisions at 25 AGeV

• STS track reconstruction:– ≥ 4 STS hits

– χ2primary vertex cut

• MuCh track finder:– track selection – hard tracks

– χ2track

• STS track reconstruction:– ≥ 4 STS hits

– χ2primary vertex cut

• MuCh track finder:– track selection – hard tracks

– χ2track

no cut on pt and opening angle!

meangauss ± 2σmeangauss ± 2σ

J/ψ simulations: cutsJ/ψ simulations: cuts

central Au+Au collisions at 25 AGeV

without cuts

— pt > 1 GeV/c

— pt > 1 GeV/c + αopening> 12˚

Nreco background pairs /event efficiencyJ/ψ (1.2×10-7)

without cuts 1.8×10-4 20%

pt > 1 GeV/c 1.5×10-6 19%

pt > 1 GeV/c + αopening> 12˚ 1.0×10-6 19%

Acceptance of reco J/ψAcceptance of reco J/ψ

without cuts % pt > 1 GeV/c %

4π

MuCh position resolutionMuCh position resolutionω→μ+μ-

position resolution

(μm)S/B

efficiency %

100 0.4 1.3

300 0.5 2.3

600 0.24 1.5

900 0.2 1.5

tracking: errorstrack extrapolation~ resolutiondetector

position resolution:—— 100μm—— 300μm—— 600μm—— 900μm

Next stepsNext steps• GEANE for MuCh track propagation

• Global tracking MuCh→TRD→ToF

• Pile-up of secondary electrons

• Realistic MuCh hit producer

• GEANE for MuCh track propagation

• Global tracking MuCh→TRD→ToF

• Pile-up of secondary electrons

• Realistic MuCh hit producer

Conclusions on muon detection in CBM

Conclusions on muon detection in CBM• Promising results for low-mass vector

mesons

• Excellent S/B ratio for J/ψ

• Promising results for low-mass vector mesons

• Excellent S/B ratio for J/ψ

Thank you for your attention!Thank you for your attention!