--- /dev/null
+// $Id$
+
+/*! \page README_sim Simulation
+
+The simulation encompasses the following tasks :
+
+- Generation of MC particles (the kinematics of the event ends up in the TreeK
+ of Kinematics#.root)
+
+- Tracking particles through the detector using
+the Virtual Monte Carlo, producing AliMUONHit objects, that end up in
+ the TreeH of MUON.Hits#.root file(s). This part is steered by AliMUON and its child
+AliMUONv1 classes.
+
+- Converting MC hits into AliMUONVDigit, called SDigits, that end up in the TreeS
+ of the MUON.SDigits#.root file(s). A S(ummable)Digit is a pad with its associated
+charge, but no noise or electronics response function applied. Steered by AliMUONSDigitizerV2 class.
+
+- Converting SDigits into Digits, by applying electronics calibrations. Actually, we de-calibrate
+ the digits at this stage, by adding a pedestal and dividing by a gain, more or less. Steered
+ by AliMUONDigitizerV3 class. Digits end up in TreeD of MUON.Digits#.root file(s). In addition,
+ for the trigger, we create AliMUONLocalTrigger, AliMUONRegionalTrigger and AliMUONGlobalTrigger objects
+at this stage, that ends up in TreeD as well.
+
+- Convert the Digits into RAW data, in a format that should be exactly the same as real data from the
+DAQ. Performed by AliMUONRawWriter.
+
+From there on, the reconstruction can proceed, in the very same way for real or simulated data,
+ as long as they are in RAW format.
+
+\section sim_s1 How to run a MUON generation
+
+You only need to run the simulation part of the test script
+AlirootRun_MUONtest.sh
+
+
+\section sim_s2 Tracking parameters, cuts, energy loss and physics processes
+
+Tracking parameters in MUON are automatically defined by GEANT
+MUON takes the default values of CUTs and physics processes
+defined by the Config files, except for the gas mixture medium
+of the tracking chambers. The CUT's and physics processes of
+the gas mixture medium is then defined in the galice.cuts file
+in the data directory. In particular ILOSS parameter MUST be
+equal unity (1) in order simulate a realistic energy loss
+distribution (mean value and fluctuations) in the active gas.
+
+\section sim_s3 Tracking of particle in the magnetic field
+
+GEANT has two ways for tracking charged particles in the
+magnetic field: HELIX et RKUTA.
+HELIX is faster and works well if the gradient of magnetic
+field is small.
+For MUON, HELIX is a not a good approximation and we must
+use RKUTA to get the optimal mass resolution of the
+spectrometer. The choice of HELIX or RKUTA is done in the
+config file when the magnetic field is defined:
+<pre>
+ AliMagFMaps* field = new AliMagFMaps("Maps","Maps", TRACKING, FACTOR, MAXB, AliMagFMaps::k5kG);
+ gAlice->SetField(field);
+</pre>
+TRACKING must be 1 for RKUTA and 2 for HELIX (the default value for aliroot is 2 (HELIX))
+FACTOR allows you to set the magnetic field to 0, just putting FACTOR=0. Default value is 1.
+MAXB is the maximum magnetic field which is 10.T
+
+\section sim_s4 MUON cocktail generator
+
+There is a MUON cocktail generator of the muon sources in the
+EVGEN directory. This class derives from AliGenCocktail.
+In the init of this class I have filled the cocktail with
+the muon sources: J/Psi, Upsilon, Open Charm, Open Beauty,
+Pion, Kaons. The code needs only the production cross section
+at 4pi (for the moment this values are in the code since I
+prefere them do not be modified), and the code calculates the
+rate of particles in the acceptance, making the scaling based
+on the number of collisions for the hard probes and on the
+number of participants for soft sources: Pions and Kaons.
+
+In the Genereate of this class all entries in the cocktail
+are called and we define a "primordial trigger" with requires
+a minimum number of muons above a Pt cut in the required acceptance.
+In order to normalized to the real number of simulated events,
+there are 2 data members in the class fNsuceeded adn fNGenerate
+which tell us what is the biais source.
+
+Enclose an example to use this generator:
+<pre>
+AliGenMUONCocktail * gener = new AliGenMUONCocktail();
+gener->SetPtRange(1.,100.); // Transverse momentum range
+gener->SetPhiRange(0.,360.); // Azimuthal angle range
+gener->SetYRange(-4.0,-2.4);
+gener->SetMuonPtCut(1.);
+gener->SetMuonThetaCut(171.,178.);
+gener->SetMuonMultiplicity(2);
+gener->SetImpactParameterRange(0.,5.); // 10% most centra PbPb collisions
+gener->SetVertexSmear(kPerTrack);
+gener->SetOrigin(0,0,0); // Vertex position
+gener->SetSigma(0,0,0.0); // Sigma in (X,Y,Z) (cm) on IP position
+gener->Init();
+</pre>
+
+\section sim_s5 How to simulate events with misaligned geometry in local CDB
+
+If you want to use a misaligned geometry to simulate some
+events you can use a local CDB. For this need to follow
+the next steps:
+
+- Generate misaligned data in local CDB.
+You can use MUONGenerateGeometryData.C as described above in
+the corresponding section. Let's assume you used the default
+residual misalignment settings, then you have a local CDB in
+your working directory called ResMisAlignCDB containing
+misalignement data (ResMisAlignCDB/MUON/Align).
+
+- Tell AliSimulation you want to use your local CDB for
+MUON/Align/Data
+To do this you need to instantiate the AliCDBManager, set the
+default storage and set the specific storage for MUON/Align/Data,
+before instantiating AliSimulation (see for example the commented
+lines AlirootRun_MUONtest.sh).
+
+<pre>
+aliroot -b >& testSim.out << EOF
+AliCDBManager* man = AliCDBManager::Instance();
+man->SetDefaultStorage("local://$ALICE_ROOT");
+man->SetSpecificStorage("MUON/align/Data","local://ResMisAlignCDB");
+AliSimulation MuonSim("$ALICE_ROOT/MUON/Config.C");
+MuonSim.SetWriteRawData("MUON");
+MuonSim.Run(10);
+.q
+EOF
+</pre>
+
+\section sim_s6 How to Merge events
+
+You can merge 2 types of simulated events. For example,
+you can simulate Hijing events, and then simulate muons
+merging both.
+
+Merging is done at the sdigits level, so Kinematics files
+of the merged events will just correspond to the
+Config.C simulated file).
+
+You must, first, do the Hijing simulation and store it
+in directory $HIJING_SIM. Note that for merging you
+won't need Kinematics files of the Hijing simulation...
+
+Hijing simulation
+
+<pre>
+aliroot -b << EOF
+AliSimulation HijingSim("$HIJING_SIM/YourConfigForHIJING.C")
+HijingSim.Run(5)
+.q
+EOF
+</pre>
+
+You cand build YourConfigFroHIJING.C File from the
+ConfigPPR file in AliRoot/macros module.
+
+Then you can do muon simulation and reconstruction
+merging both simulated events. In next example, we are
+merging 20 times each Hijing event in order to simulate
+100 muons merged with 5 Hijing events.
+
+<pre>
+aliroot -b << EOF
+AliSimulation MuonSim("$ALICE_ROOT/MUON/Config.C")
+MuonSim.MergeWith("$HIJING_SIM/galice.root",20) //parameters are the Hijing simulation file and the number of times we use each Hijing event
+MuonSim.Run(100) // number of muon (Config.C) events
+.q
+EOF
+
+
+aliroot -b << EOF
+TPluginManager * pluginmanager = gROOT->GetPluginManager()
+pluginmanager->AddHandler("AliReconstructor","MUON","AliMUONReconstructor","MUON","AliMUONReconstructor()")
+AliReconstruction MuonRec("galice.root")
+MuonRec.SetRunTracking("")
+MuonRec.SetRunVertexFinder(kFALSE)
+MuonRec.SetRunLocalReconstruction("MUON")
+MuonRec.SetFillESD("MUON")
+MuonRec.Run()
+.q
+EOF
+</pre>
+
+\section sim_s7 On track numbering
+
+All generated particles, including primary and secondary
+particles are put on the stack. The secondary particles are kept
+in the stack only if they gave a hit in *any* of the ALICE detectors
+The number of all particles placed on the stack for a given event
+can be obtained with
+Int_t nPart = AliStack::GetNtrack();
+Looping from 0 to nPart via AliStack::Particle(ipart)
+gives the particle listing as obtained from the particle generator (primaries)
+and Monte Carlo (secondaries).
+
+The particle response in the detector, a hit, is registered
+in the hits tree and the hits are filled with each primary track.
+The total number of "tracks" (fills of the tree) can be obtained
+with ntracks = AliMUONMCDataInterface::NumberOfTracks(event) and is usually smaller than "nPart".
+Since particles can also deposit hits in other detectors than
+the MUON spectrometer, there will be many "tracks" (fills) in the hit-tree
+without a hit in MUON.
+
+The correspondence between "track ID" in the hits-tree ("itr") and the
+particle ID for particles on the stack (i.e. generated particles) can be
+obtained via:
+<pre>
+for (Int_t itr = 0; itr < ntracks; itr++) {
+ AliMUONVHitStore* hitStore = mcDataInterface.HitStore(event,itr);
+ //track "itr" of the hits-tree
+ Int_t nhitstot = hitStore->GetSize();
+ AliMUONHit* mHit;
+ TIter next(hitStore->CreateIterator());
+ while ( ( mHit = static_cast<AliMUONHit*>(next()) ) )
+ {
+ Int_t id = mHit->Track(); //gives particle ID on stack
+ TParticle* particle = mcDataInterface.Stack(event)->Particle(id);
+ }
+}
+</pre>
+
+where mcDataInterface has been obtained by
+AliMUONMCDataInterface mcDataInterface("galice.root");
+
+During the procedure to go from hits to digits, the hits
+are summed up such that more than one track can contribute
+to a given digit. As a consequence the method
+Int_t AliMUONDigit::Track(Int_t trackID)
+takes an argument, where "trackID" runs from 0 to
+AliMUONDigit::Ntracks() to provide the reference to *all*
+tracks that contributed to it. The returned track ID is the one
+referred to in the hit-tree. To know which is the generated particle
+that deposited a given digit one has to follow the sequence of the kind:
+(shown here using the simple, but not fast, DataInterface interfaces) :
+
+<pre>
+AliMUONMCDataInterface mcdi("galice.root");
+AliMUONDataInterface di("galice.root");
+
+AliMUONVDigitStore* digitStore = di.DigitStore(event);
+AliMUONVDigit* mDigit = ... get some digit from the digitStore
+
+for (int tr = 0; tr < mDigit->Ntracks(); tr++)
+{
+ Int_t hitTrackID = mDigit->Track(tr);
+ // get the hits corresponding to this trackID
+ AliMUONHitStore* hitStore = mcdi.HitStore(event,hitTrackID);
+ // loop over the hits
+ TIter hNext(hitStore->CreateIterator());
+ AliMUONHit* mHit;
+ while ( ( mHit = static_cast<AliMUONHit*>(hNext()) ) )
+ {
+ Int_t numPart = mHit->Track(); //gives ID of particle on the stack
+ Int_t idTrack = mHit->Particle(); //gives flavour code of the particle
+ }
+}
+</pre>
+
+This chapter is defined in the READMEsim.txt file.
+
+*/
git://git.uio.no / u / mrichter / AliRoot.git / blobdiff