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da0e9ce3 | 1 | //------------------------------------------------------------------------------// |
2 | EvtGen is a particle decay simulator specifically designed for the needs of | |
3 | B-physics studies. Complete manual of EvtGen is available at address: | |
4 | http://robbep.home.cern.ch/robbep/EvtGen/GuideEvtGen.pdf | |
5 | //------------------------------------------------------------------------------// | |
6 | ||
7 | [14/12/2009] | |
8 | 1)This module contains: | |
9 | ||
10 | - EvtGen original code organized in three directories: | |
11 | EvtGenBase-EvtGenModels-EvtGen. EvtGenModels directory contains all models | |
12 | avilable in EvtGen to decay particles. | |
13 | ||
14 | - The interface classes AliGenEvtGen and AliDecayerEvtGen for AliRoot users: | |
15 | the methods to decay particles are in AliDecayerEvtGen which represents | |
16 | the implementation of AliDecayer using EvtGen package | |
17 | ||
18 | 2)EvtGen required libphotos.so to generate Final State Radiation. Photos code is | |
19 | located in PHOTOS directory. | |
20 | ||
21 | 3)The implemented cases to force beauty hadrons interest those channels: | |
22 | B->J/psi+X - B->J/psi+X,J/psi->e-e+ - B->J/psi+X,J/psi->mu-mu+ - B->e+X. | |
23 | Those are decayed by exclusive models of EvtGen, and all parameters and | |
24 | models used to decay them are not modified with respect to the official | |
25 | EvtGen release. Some of particles produced in the decay chain (i.e. Lamda_c | |
26 | from Lambda_b, Xi_c0 from Xi_b-, etc...) are decayed by Pythia with the | |
27 | configuration setting in the AliDecayerPythia. | |
28 | ||
29 | 4)Polarization is still to be implemented in the interface classes. | |
30 | It would be done soon. | |
31 | ||
32 | 5)To use EvtGen to decay beauty particles adjust those lines in the Config.C: | |
33 | ||
34 | //----- load libraries (after loading libpythia6.so) | |
35 | gSystem->Load("libphotos.so"); | |
36 | gSystem->Load("libEvtGenBase"); | |
37 | gSystem->Load("libEvtGenModels"); | |
38 | gSystem->Load("libEvtGen"); | |
39 | gSystem->Load("libTEvtGen"); | |
40 | ||
41 | //----- declare an AliGenCocktail | |
42 | AliGenCocktail *generCock=new AliGenCocktail(); | |
43 | generCock->UsePerEventRates(); | |
44 | ||
45 | //----- declare Pythia configuration: switch-off beauty decays in Pythia | |
46 | AliGenPythia *pythia= ..... | |
47 | .... | |
48 | pythia->SetForceDecay(kNoDecayBeauty); | |
49 | ||
50 | //----- declare EvtGen configuration and put the two generators in the cocktail | |
51 | AliGenEvtGen *gene = new AliGenEvtGen(); | |
52 | gene->SetForceDecay(kBJpsiDiElectron); | |
53 | gene->SetParticleSwitchedOff(AliGenEvtGen::kBeautyPart); | |
54 | generCock->AddGenerator(pythia, "Pythia", 1.); | |
55 | generCock->AddGenerator(gene,"gene",1.); |