SIS-100 simulationSIS-100 simulation

Partha Pratim BhaduriSubhasis Chattopadhyay

VECC, Kolkata

p-A simulation for J/ at SIS-100

Much geometry optimization for SIS-100

p-A simulation

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Motivation

• The aim of the relativistic heavy-ion collisions is to study the onset of de-confinement and the properties of the de-confined media in the laboratory. Hence it is necessary to define unambiguous and experimentally viable probes for de-confinement.

• In this respect proton-nucleus (p+A) collisions must be a fundamental component of any heavy-ion physics program

• Defines the reference baseline relative to which we recognize HI specific phenomena

• p+A collisions provide a measure of the nuclear effects – helps in disentangling the “QGP” effect from the “non-QGP” effects. Here there is no formation time for the “secondary” medium , hence such collisions provide as essential tool to correctly account for the effect of the nuclear medium initially present.

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System

• The specifications of the system chosen are:

Target : Au, Cu, S, O, C Projectile : p (1, 1) Beam energy : 30 GeV Event generator used : HSD – 2.5 Events : 5,000 (ISUBS = 50, NUM = 100)

Results with HSD

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J/ pseudo-rapidity distribution

pCpOpSpCupAu

pCpOpSpCupAu

CMS Frame Laboratory Frame

J/ transverse momentum spectra

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pCpOpSpCupAu

HSD vs. Pluto (muon pseudo-rapidity distribution)

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HSD Pluto

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CMS Frame Laboratory Frame

Laboratory Frame

Muons decayed from J/ Isotropic decay in J/ rest frame

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CbmRoot Version: Trunk version

Number of events : 4000

Much geometry : Standard Geometry

• 2 layers in 5 stations

• Distance between layers 10 cm.

• Gap between absorbers 20 cm

• 3 layers at the last trigger station

• Total 13 layers

• Total length of Much 350 cm

Signal : J/ decayed muons from HSD for p+Au system for 30 GeV p beam

Background : central UrQMD events for p+ Au at 30 GeV/n

Much Hit producer w/o cluster & avalanche

L1(STS) & Lit (Much) tracking with branching

Simulation

Absorber thickness (cm):20 20 20 30 35 100

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Analysis

• Use the reconstructed data after the full tracking through the detector set-up.

• Reconstructed global tracks have to satisfy :

1. Fraction of true hits (truehits/(true hits+ wrong hits+fake hits) >= 0.7

2. No. of STS Hits associated with the global track >=4

3. No. of Much Hits associated with the global track >=10

4. Chi2 primary <=2

Detector Acceptance

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Raw HSDLayer # 1Layer # 3Layer # 5Layer # 7Layer # 9Layer # 11

Invariant mass spectra

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Embedded Reconstruction efficiency : 23.8 %

Pure HSDReconstruction efficiency : 25 %

Negligible background effect

Geometry optimization

• Our aim is to optimize the geometry of the muon set-up for SIS-100.

• Optimization should be done with low mass vector mesons (lmvms) rather than J/ψ and at the lowest available energy.

• J/ψ measurements due to low background after more than 2 m of Fe are not so sensitive to the muon setup as the measurements of muons from LMVM.

• Issue is to reconstruct the soft muons ( eg: ω→μμ )

• We have chosen central Au+Au events at 8 AGeV together with ω→μμ.

• Use the same set-up 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.

• Statistics : 10k central events

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

Absorber thickness (cm):20 20 20 30 35 100

Reconstruction efficiency : 0.5 % Estimated Signal : 645.234 Estimated Bkg. : 573.028 S/B : 1.126

Cuts :1.No. of Much hits>=92.70 % true hit3.No. of STS Hits >=4

Number of stations : 13(2+2+2+2+2+3)Absorber to station distance : 5 cm.Layer to layer distance : 10 cm.

Super event (SE) analysis for bkg.Gaussian fit to signalPolynomial fit to bkg.

Cuts :1.No. of Much hits>=92.70 % true hit3.No. of STS Hits >=4

Option II : Reduced geometry

Absorber thickness (cm):20 20 30 35 100

Number of stations : 11(2+2+2+2+3)Absorber to station distance : 5 cm.Layer to layer distance : 15 cm.

GEM Modules : 25.6 cm. * 25.6 cm.# of modules : 1928

Super event (SE) analysis for bkg.Gaussian fit to signalPolynomial fit to bkg.

Reconstruction efficiency : 1.6 % Estimated Signal : 3997.52 Estimated Bkg. : 30052.1 S/B : 0.133

Cuts :1.No. of Muchhits>=72.70 % true hit3.No. of STS Hits >=4

Option III : Reduced Geometry

Number of stations : 9 (3+3+3)Absorber to station distance : 10 cm.Layer to layer distance : 10 cm.

Absorber thickness (cm):30 70 125

Super event (SE) analysis for bkg.Gaussian fit to signalPolynomial fit to bkg.

Reconstruction efficiency : 1.4 % Estimated Signal : 2874.44 Estimated Bkg. : 9936 S/B : 0.2866

Cuts :1.No. of Muchhits>=72.70 % true hit3.No. of STS Hits >=4

GEM Module : 25.6cm.*25.6 cm.

# of Modules : 1512

Comparison of different geometries

configuration # of stations

Total absorber thickness (cm.)

Much Hit cut

Reco. eff

S/B

Standard 13 125 >=9 0.5 % 1.126

Reduced – I 11 105 >=7 1.6 % 0.133

Reduced - II 9 100 >=5 1.4 % 0.287

To do list …..

• Continue the study with 9 station configuration but with same total absorber thickness (125 cm.)

• Test the configuration for charmonia• Study of gaps ( station to station & station to

absorber)