SIS100 simulation(Geometry optimization)

Partha Bhaduri (VECC)Arun Prakash(BHU)

Motivation

Physics performance analysis for SIS-100.

Determine a “standard” version of Much for SIS-100.

Look for an optimized version of Much for SIS-100.

This optimized version will be used for subsequent physics analysis.

• Optimization should be done with low mass vector mesons

(lmvms) and J/ψ at SIS100 energy.

• We have chosen central Au+Au events at 8 AGeV and pAu

collisions @ 30 GeV .

• Use the same set-up for in simulation for J/ψ & LMVM. For

LMVM use information from stations just before the last thick

absorber.

• Run full simulation & obtain signal reconstruction efficiency &

S/B ratio.

– We have to decide upon :– Total number of stations(layers)– Total absorber thickness, total no. of absorbers & the

absorber material– Number of stations (2/3) in between two absorbers– Distance between stations & absorber to station distance

– Present constraints :– Absorber material (Fe, Pb, W )– Layer to layer distance >= 10 cm.– Layer to absorber distance >= 5cm.

Geometry (Dec 2009), LMVM setup)

Transport:1000 UrQMD mbias @8A.GeV+1000 OmegaGeometry: Compact +Modular+32cmX32cm GEMsts_same_z.geopipe_much.geoshied_standard.geocave.geotarget_au_250mu.geomagnet_standard.geo

Station radii

R_max+20cm R_max+0.6cm

Station-1Station-1

R=70cm

Decided to remain within nominal outer radius at each station (no extra radii), adds pad

multiplicity artificially

Particle density

The kink ???

Segmentation : First attempt, guided by particle density

Item Pads

No of regions

2 2 2 1 1

No of Channels

256 256 256 256 256 ~636k

V1 R int 32 50 70 - -

Lx 0.5 0.5 1.0 - -

Ly 0.5 0.5 1.0 - -

Rout 70 96 120 150 182.5

Lx 1.0 1.0 2.0 2.0 2.0

Ly 1.0 1.0 2.0 2.0 2.0

Av. Hit loss ~ 1.5%

Item Pads

No of regions

1 1 1 1 1

No of Channels

256 256 256 256 256 ~430k

V2 R int - - - - -

Lx - - - - -

Ly - - - - -

Rout 70 96 120 150 182.5

Lx 1.0 1.0 2.0 2.0 2.0

Ly 1.0 1.0 2.0 2.0 2.0

How bad can it be ?

Av hit loss ~4.8%

Item Pads

No of regions

1 1 1 1 1

No of Channels

256 256 256 256 256 ~120k

V3 R int - - - - -

Lx - - - - -

Ly - - - - -

Rout 70 96 120 150 182.5

Lx 2.0 2.0 4.0 4.0 4.0

Ly 2.0 2.0 4.0 4.0 4.0

Can we worsen it further ?

Av hit loss ~ 14.8%

Item Pads

No of regions

2 2 1 1 1

No of Channels

256 256 256 256 256 ~528k

V4 R int 25 40 - - -

Lx 0.5 0.5 - - -

Ly 0.5 0.5 - - -

Rout 70 96 120 150 182.5

Lx 1.0 1.0 2.0 2.0 2.0

Ly 1.0 1.0 2.0 2.0 2.0

Next stage : fine tuning

Av. Hit loss ~2.20%

segmentation station-1 station-2 station-3

station-4station-5

pads~528k

Hits Simple Gem

Hits Advanced GEM

Occupancy increases inadvanced GEM by factor of~3compared to Simple GEM.CONSEQUENCES FOR DETECTOR FABRICATION

SIS -100 Geometry : version 1To start with we have used a geometry with total 9 stations with (3+3+3) configuration. Effective no. of stations for lmvm is thus 6.

Total abs. thickness:

lmvm : 100 cm. (30 +70)

J/Psi : 225 cm. (30+70+125)

Specification of distances :

layer to layer : 10 cm.

abs. to layer : 0 cm.

layer to absorber : 10 cm.

Extra Radius (change in CbmMuchGeoscheme class) :

station : 0 cm.

absorber : 100 cm.( to keep stations inside absorber)

Simulation (AA) Transport : Central Au+Au @ 8A GeV

Signal : Pluto (ω→μμ) Background : UrQMD Events : 10k

Reconstruction : Segmentation scheme : Manual segmentation

Station 1 (layers 1, 2, 3) : 2 regions (pad size in the central region : 0.2 – 0.6 cm.)

Station 2 (layers 4, 5, 6) : one region with pad size 3.2 cm * 3.2 cm.

Station 3 (layers 7, 8, 9) : one region with pad size 5 cm.*5 cm.

Implementation of detector in-efficiency at hit producer level. Simple Hit producer w/o clustering

Eta distribution @ station 1

Signal muons Primary Bkg.

Input tracks

Primary tracks hitting station 1

Midrapidity not covered??

Momentum distribution @ station 1

Signal muons Primary Bkg.

Input tracks

Primary tracks hitting station 1

Azimuth distribution @ station 1

Signal muons Primary Bkg.

Input tracks

Primary tracks hitting station 1

Acceptance of primaries @ station 1

Input tracks

Primary tracks hitting station 1

Signal muons Primary Bkg.

Implementation of detector in-efficiency

No loss

10% hit loss

No hit loss

No hit loss

5% hit loss

5% hit loss

Effect of hit loss on reconstructed tracks

Global tracks

Much tracks

Signal Tracks

Background tracks

Distribution of chi2vertex

Invariant mass spectrum (ω→μμ )

Cuts :1. No. of Muchhits>=42. No. of STS Hits >=43. chi2primary < 3

Super event (SE) analysis for bkg (combine all the positive tracks with all the negative tracks over all the events excluding only tracks from same event). Gaussian fit to signalPolynomial (pol 8) fit to bkg.

10k central embedded events for Au + Au @ 8

GeV/n

Pad size (centre of station #1 )

Total Pads Reconstruction efficiency (%)

S/B

3 mm. 523332 1.74 0.0027

4 mm. 309384 1.77 0.0027

5 mm. 227556 1.64 0.0029

6 mm. 167904 1.64 0.0030

Results for various pad size (ω→μμ )

Invariant mass spectra (I/Psi)

Super event (SE) analysis for bkg (combine all the positive tracks with all the negative tracks over all the events excluding only the tracks from the same event). One signal event in 10^7/BR bkg events Gaussian fit to signalPolynomial (pol 7) fit to bkg.

Cuts :No. of Muchhits >= 7No. of STS Hits >= 4Chi2primary < 3

Reconstruction efficiency : 5.1 %

S/B : 18.9

pA: Acceptance of reconstructed pairs

Background Signal

Conditions : 70% true hits

4 STS hits + 7 MUCH layers Same geometry as AA

5mm pad size at the inner region

of station 1

Polynomial of order 8 fitting to background

Reco. eff. 20.2 %

S/B : 127

pA: 30 GeV

Conditions : 70% true hits

4 STS hits + 7 MUCH layers

Work in progress

w/o 70% criterion

SUMMARY:

First step of optimization done for SIS10 MUCH

Comparisons will be made with other geometry options

(absorber/no of stations)

Clustering will be added. (should not have large effect as

GEM cluster size ~100 micron)

Minimum pad size of 4 mm seems reasonable and we plan to

build one test chamber with these.

pA results needs to be updated.

Study of J/Psi (AuAu)

Cuts :1.No. of Muchhits>=72. No. of STS Hits >=43.Chi2primary <3

Run the full simulation chain for J/Psi with 4mm. pad size

10k central Au+Au embedded events @ 8 GeV/n

Only bkg. Track (UrQMD generated)

from different events for SE

All tracks (uncorrelated signal muons+ bkg. Tracks) from

different events for SE