Experience With CBM Muon Simulation

Partha Pratim Bhaduri

Present structure of CBM simulation framework

Simulation package consists of:1. Cbmsoft2. Cbmroot The .tar.gz files have been kept at http://

www.veccal.ernet.in/~pmd/public_html/FAIR/prem/Few more words about the framework: Cbmsoft:• transport(geant3,geant4,vmc etc.)• tools(root packages)• generators ( Pluto,Pythia etc.)

Cbmroot (Cbm specific working directory) consists of:

Directories written in red are directly related to Much-simulation

• L1 /OffLineInterface• base• build -> Installation Directory• generators• geometry• ecal• sts -> Main detector • rich• much• tof• macro and so on.

macro (detailed structure):It consists of all the working macros.

We work at cbmroot/macro/much/

It contains all macros for reconstruction of much tracks.

Reconstruction process involves:

1)First run Much Simulation code (much_sim.C).

•With both Pluto (giving primary muons) and

URQMD (background).

Much simulation generates several hits in different detectors like sts , tof , much.

They are called as Stspoints,Muchpoints and so on.

2) Then run Sts Reconstruction code(rec_sts_fast.C or sts_reco.C)

Reconstruct tracks in sts (two options – ideal tracking and L1 tracking).

3)Then run much reconstruction code(much_reco.C)

Reconstruct the tracks in Much detector (extrapolating sts-tracks).

Contd..

Looking at the results:Looking at the results:

Took Much tracks & much momenta, saw mass-peak, but at lower mass

Took MUCH tracks, but momenta from sts tracks, peak at expected position

Muon Chambers

Fe Fe Fe Fe FeFe Fe Fe Fe Fe

20 20 2

0 30

35 cm

20 20 2

0 30

35 cm

102.5 cm0 cm10 cm

260 cm

First Look at single MUCH (HARD) tracks (composition of associated particles)

2000 URQMD+PLUTO events Mostly muon tracks, rest pions, kaons and protons

PID distribution

Reconstructed J/Psi Muon-multiplicity distribution

• Muon eff: 40%• Fraction of decay muon in sample: 1.1%• Kaon+proton fraction: 9.5%• Pion fraction: 25%

Background track distribution

Invariant mass distribution (all hard tracks –proton,kaon)

Area under peak/area away from peak = 1.57 (note: bkg not under the peak)

No other cuts applied

Some Modifications of the previous results

Idea:•Take Decay into account.

•Find the particle-ids from the muchhits rather than maching tracks.

•Then compare with matchtracks.

Result:•This gives correct no. of decayed muons.

•Reduces pion fraction

•But giving some anamoly. Most of the muons (secondary) are decayed before reaching the first muon station.

Modified Results:

Muon Fraction: 85%

Signal Muons:81%

Decay Muons:19%

Pion Contribution:94%

Pion Fraction:8%

Kaon fraction:6%

Efficiency of STS:58.5 %Efficiency of Much: 39%

Much Tracks STS Tracks

Next steps:

1. Implementation of granularity in muon chamber:Approach: (a) create cells/strips on the chamber (b) If there are more than one hit in one cell/strip, ignore rest, take only first one. Prelim: with 1cm x 1cm cell size, NO double hits for chamber > 6, Details are being worked out. (c ) For strips, centroid to get the position

2. Mixed events for background estimation

3.Optimization of geometry for J/Psi