Getting started with musrSim

November 3, 2009Tsutomu Mibe

(KEK)

Preparation• unzip musrSim.zip• cd musrSim• make• Add low energy EM data files

– Goto http://geant4.web.cern.ch/geant4/support/download.shtml– Click “download”

– su– cd /opt/heplib/Geant4/– gtar zxf G4EMLow6.2.tar.gz– exit

• export G4LEDATA=/opt/heplib/Geant4/data/G4EMLOW6.2• cd run• copy example01.mac to this directory.

Example 01

• example01.mac• Target:– vacuum

• Detector:– No detector

• Beam:– Stopped mu+ at (z,y,z)=(0,0,0)

Running example01.mac (1)

Running example01.mac (2)

• Close the VRML View Pro window• A mu+ generates and decays.• A new window with decay particles pops-up.

Geant session ends after this window is closed.

Turning off visualization

• The visualization of the geometry and particles can be turned off by modifying example01.mac as shown on the right.

Increasing number of events

• Number of events can be changed by changing the number after /run/beamOn.

Let’s run again

• No window appears at this time.• A new data file is generated under ./data/

• cd data• root musr_0.root

– “t1” is a name of the output root tree.– A command t1->Print() will provide list of contents

positron momentum• x-component of the positoron momentum vector• t1->Draw(“posIniMomX”)

positron momentum

• t1->Draw(“sqrt(posIniMomX^2+posIniMomY^2+posIniMomZ^2)”)

positron angle• Polar angle (angle between z-axis and positron)• t1->Draw(“posIniMomZ/

sqrt(posIniMomX^2+posIniMomY^2+posIniMomZ^2)”)

cosq

End root session

Exercises1. Generate 10000 events.

2. Draw following distributionsa. positron angle vs momentumb. muon decay positions (muDecayPos*) (*=X,Y,Z)c. muon polarization at decay (muDecayPol*)d. muon decay time (muDecayTime)

3. Fit the exponential function to the muon decay time distribution and obtain lifetime

4. Check positron angler distribution and momentum distribution is consistent with the expectation from the weak interaction theory.

appendix

My G4 environmental variables