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da0e9ce3 | 1 | //------------------------------------------------------------------------------// |
2 | EvtGen is a particle decay simulator specifically designed for the needs of | |
0ca57c2f | 3 | B-physics studies. Complete manual of EvtGen is available at: |
4 | http://robbep.home.cern.ch/robbep/EvtGen/GuideEvtGen.pdf. Further information | |
5 | can be found on the EvtGen official web site http://evtgen.warwick.ac.uk/src/ | |
6 | The EvtGen release installed here is taken from | |
7 | http://svnweb.cern.ch/guest/evtgen/tags/R01-03-00 | |
da0e9ce3 | 8 | //------------------------------------------------------------------------------// |
9 | ||
3a6cdcc8 | 10 | [28/05/2014] |
da0e9ce3 | 11 | 1)This module contains: |
12 | ||
0ca57c2f | 13 | - EvtGen original code organized in four directories: |
14 | EvtGenBase-EvtGenModels-EvtGen-EvtGenExternal. | |
15 | EvtGenModels directory contains all models avilable in EvtGen to decay | |
16 | particles. EvtGenExternal contains the "interface" class with the external | |
17 | packages | |
da0e9ce3 | 18 | |
19 | - The interface classes AliGenEvtGen and AliDecayerEvtGen for AliRoot users: | |
20 | the methods to decay particles are in AliDecayerEvtGen which represents | |
21 | the implementation of AliDecayer using EvtGen package | |
22 | ||
0ca57c2f | 23 | 2)The external packages, interfaced with EvtGen by EvtGenExternal class, |
24 | are used to generate specific particle decays and | |
25 | are located in the TEvtGen subdirectories (except for Pythia8): | |
da0e9ce3 | 26 | |
0ca57c2f | 27 | - HepMC (http://lcgapp.cern.ch/project/simu/HepMC/download/HepMC-2.06.08.tar.gz) |
28 | The HepMC package is an object oriented event record written in C++ for High Energy | |
29 | Physics Monte Carlo Generators. | |
30 | ||
31 | - Tauola (http://tauolapp.web.cern.ch/tauolapp/resources/TAUOLA.1.1.4/TAUOLA.1.1.4.tar.gz) | |
32 | C++ interface of Tauola code, specifically designed to generate tau decays. | |
33 | ||
34 | - Photos (http://photospp.web.cern.ch/photospp/resources/PHOTOS.3.54/PHOTOS.3.54.tar.gz) | |
35 | C++ interface of Photos code, specifically designed to generate Final State Radiation. | |
36 | ||
37 | - Pythia8 (available in $ALICE_ROOT/PYTHIA8/) | |
38 | ||
39 | ||
40 | 3)The "default" decay table with all particles and all decay channels | |
41 | can be found in TEvtGen/EvtGen/DECAY.DEC. The definition of all | |
42 | particles is done in the table "evt.pdl". Both tables (DECAY.DEC and evt.pdl) | |
43 | are loaded during the initialization of EvtGen. Several decay tables are available | |
44 | in the directory TEvtGen/EvtGen/DecayTable and are used to generate "forced" decay modes. | |
45 | All parameters, models and BR used in these tables are not modified with respect | |
46 | to the official EvtGen release. | |
3a6cdcc8 | 47 | The following decay tables are tested: BTOD.DEC, BTOELE.DEC, BTOJPSI.DEC, BTOJPSITOELE.DEC, |
48 | BTOJPSITOMU.DEC. | |
da0e9ce3 | 49 | |
50 | 4)Polarization is still to be implemented in the interface classes. | |
da0e9ce3 | 51 | |
0ca57c2f | 52 | 5)Below an example of the usage of EvtGen in AliRoot to decay beauty particles. |
53 | The following lines should be added in the Config.C: | |
3a6cdcc8 | 54 | // set the xmldoc path using PYTHIA8DATA enviroement var |
55 | gSystem->Setenv("PYTHIA8DATA", gSystem->ExpandPathName("$ALICE_ROOT/PYTHIA8/pythia8175/xmldoc")); | |
da0e9ce3 | 56 | |
0ca57c2f | 57 | //----- load libraries |
58 | gSystem->Load("libHepMC.so"); | |
59 | gSystem->Load("libTauola.so"); | |
60 | gSystem->Load("libpythia8.so"); | |
61 | gSystem->Load("libPhotos.so"); | |
da0e9ce3 | 62 | gSystem->Load("libEvtGen"); |
0ca57c2f | 63 | gSystem->Load("libEvtGenExternal"); |
da0e9ce3 | 64 | gSystem->Load("libTEvtGen"); |
65 | ||
66 | //----- declare an AliGenCocktail | |
67 | AliGenCocktail *generCock=new AliGenCocktail(); | |
68 | generCock->UsePerEventRates(); | |
69 | ||
70 | //----- declare Pythia configuration: switch-off beauty decays in Pythia | |
71 | AliGenPythia *pythia= ..... | |
72 | .... | |
73 | pythia->SetForceDecay(kNoDecayBeauty); | |
74 | ||
75 | //----- declare EvtGen configuration and put the two generators in the cocktail | |
76 | AliGenEvtGen *gene = new AliGenEvtGen(); | |
77 | gene->SetForceDecay(kBJpsiDiElectron); | |
78 | gene->SetParticleSwitchedOff(AliGenEvtGen::kBeautyPart); | |
79 | generCock->AddGenerator(pythia, "Pythia", 1.); | |
80 | generCock->AddGenerator(gene,"gene",1.); |