Experience With CBM Muon Simulation Partha Pratim Bhaduri

Present structure of CBM simulation framework  Simulation package consists of: 1.Cbmsoft 2.Cbmroot The.tar.gz files have been kept at m/ m 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: 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 Fe cm cm0 cm 10 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