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