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MUON Evaluation

How to process invariant mass spectra for J/psi or Upsilon

The macro MUONmassPlot_ESD.C reads back the MUON ESD informations and compute the invariant mass spectra and corresponding uncorelated background. Moreover gives the number of event in the resonance peak and the number of triggers.

root [0] .L $ALICE_ROOT/MUON/MUONmassPlot_ESD.C+
root [1] MUONmassPlot_ESD(ExtrapToVertex, 
      geoFilenam, filename
                        FirstEvent, LastEvent, 
      ResType, Chi2Cut,
      PtCutMin, PtCutMax,
            massMin, massMax)
ExtrapToVertex (default -1)
      <0: no extrapolation;
      =0: extrapolation to (0,0,0);
      >0: extrapolation to ESDVertex if available, else to (0,0,0)
geoFilename (default "geometry.root") geometry file name needed to extrap to vertex
filename    (default "galice.root") galice root file name
FirstEvent  (default 0)
LastEvent   (default 10000)
esdFileName (default "AliESDs.root") esd root file name
ResType     (default 553):   553 for Upsilon, anything else for J/Psi
Chi2Cut     (default 100):   keep only tracks with chi2 per d.o.f. < Chi2Cut
PtCutMin    (default 1):     keep only tracks with transverse momentum > PtCutMin
PtCutMax    (default 10000): keep only tracks with transverse momentum < PtCutMax
massMin     (default 9.17 for Upsilon) keep only invariant masses with 
massMax     (default 9.77 for Upsilon) massMin < mass < massMax

How to run MUONRecoCheck macro

To check the muon reconstruction by comparing the reconstructed tracks with the reference tracks made of "AliTrackReference" for the hits in chamber (0..9) and kinematic informations (TreeK) for the vertex. This macro can be used to check the track reconstruction e.g. efficiency, momentum resolution ... but also to make physics analysis whenever track identification is needed.

To compile MUONRecoCheck.C

.includepath $ALICE_ROOT/STEER
.includepath $ALICE_ROOT/MUON

To run MUONRecoCheck

MUONRecoCheck(nEvent,"geometry.root", "galice.root"); // nEvent = nb of events

Macros for MC studies

For MC studies the classes AliMUONTrackLight and AliMUONPairLight can be used in order to fill not only the single muon / dimuon's kinematics (charge, pT, rapidity, etc) at the generation AND reconstruction level, but also for "decoding" the Pythia output and for the storing of the single muon's history. This allows to tag if two muons of a given event come from a certain, well-defined process, such as J/psi, Upsilons, correlated open charm or open beauty or the low masses or if they are of uncorrelated origin. For open beauty/charm it also tags the creation process (pair creation, flavour excitation or gluon splitting). The classes also allow to tag feed-down or neutral B meson oscillation and has a method that checks whether the reconstructed track is a muon or not.

The macros ReadRecoCocktail.C, DecodeRecoCocktail.C and MergeMuonLight.C are examples how to use these two classes. DecodeRecoCocktail.C opens the generated files, loops over the events and fills an AliMUONTrackLight object for every reconstructed track for which the reference to its generated particle could be established, using the AliMUONRecoCheck class. It then takes the AliMUONTrackLight objects and forms - event by event - AliMUONPairLight objects, on a combinatorial basis. For a given event these objects are stored in respective TClonesArrays which are then stored in a tree. By default, the produced output file is called "MuonLight.root". This root file can then be taken by the macro "ReadRecoCocktail.C" that shows, on the example of the reconstructed mass and pT of the AliMUONPairLight object, how to access the available information. For large statistics, in which many individual MuonLight.root files are produced, MergeMuonLight.C can be used to merge the files and produce one common output root file.

To read a generation/reconstrution from PDC06 preproduction, and write a file with a tree of AliMUONTrackLight / AliMUONPairLight : go to the directory containing the generation/reconstruction. From there run aliroot

.L DecodeRecoCocktail.C+

To read the file previously generated:

.L ReadRecoCocktail.C+

This chapter is defined in the READMEevaluation.txt file.