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e66c7726 | 1 | // Author: Leticia Cunqueiro |
2 | ||
3 | //Some explanations: | |
4 | //if fpythia==1, quenched pythia (qpythia) is configured. | |
5 | //if fpythia==2, pyquen afterburner applyed | |
6 | ||
7 | // The list of avaliable tunes can be checked in $ALICE_ROOT/PYTHIA6/pythiaX.f , inside subroutine PYTUNE | |
8 | // Note that if you are using QPYTHIA , it only works with Q2-ordered showers, that is tune<300. | |
9 | //More modern tunes are pt-ordered and use a different FSR shower. | |
10 | ||
11 | //In the implementation of qpythia in aliroot I set as default the following computation of the geometry: | |
12 | // -Glauber to determine the overlapping region of the nuclei and the impact parameter of the collision | |
13 | // -Random sampling of the initial coordinates of the hard scattering in the overlapping region | |
14 | // -Given the coordinates and direction of each parton in the shower, calculate the path length to the "end" | |
15 | // of the medium and the integrated qhat along this path length, alla PQM. | |
16 | ||
17 | //In the PQM approach, you integrate the qhat(dx,dy) along the path length and this is purely geometrical. See formula (13) in http://arxiv.org/pdf/hep-ph/0406201.pdf | |
18 | //There is a free parameter k (in fm), that sets the scale of the transport coefficient. In 0-10% PbPb collisions, | |
19 | //the average <qhat> and k are related via a number: | |
20 | // <qhat>/k =5.87 e^-5 fm^-4 | |
21 | //If you want a <qhat> of 10 GeV2/fm, | |
22 | // 10 /5.87e^-5 (GeV2 fm^3)=k | |
23 | //If you want k in fm then you have to divide by the squared of hbarc (hbar c=0.197 GeV fm) | |
24 | // This gives k=4.4e^6 fm, which is the quench value we set in SetQhat | |
25 | ||
26 | AliGenerator* AddMCGenQuench(Float_t e_cms = 2760., Double_t ptHardMin = 0., Double_t ptHardMax = 0., Int_t fpythia = 1, Double_t quench=4.4e6) | |
27 | { | |
28 | //Add Pythia generator: pt-hard bin or min bias | |
29 | ||
30 | gSystem->Load("liblhapdf.so"); | |
31 | ||
32 | return CreatePythia6Gen(e_cms, ptHardMin, ptHardMax, fpythia, quench); | |
33 | } | |
34 | ||
35 | AliGenerator* CreatePythia6Gen(Float_t e_cms, Int_t ptHardMin, Int_t ptHardMax, Int_t fpythia, Double_t quench) { | |
36 | ||
37 | gSystem->Load("libqpythia.so"); | |
38 | gSystem->Load("libEGPythia6.so"); | |
39 | gSystem->Load("libAliPythia6.so"); | |
40 | ||
41 | AliGenPythia* genP = new AliGenPythia(1); | |
42 | ||
43 | // vertex position and smearing | |
44 | genP->SetVertexSmear(kPerEvent); | |
45 | ||
46 | // charm, beauty, charm_unforced, beauty_unforced, jpsi, jpsi_chi, mb | |
47 | if (ptHardMin>0.) { | |
48 | genP->SetProcess(kPyJets); | |
49 | genP->SetPtHard((float)ptHardMin,(float)ptHardMax); | |
50 | } else | |
51 | genP->SetProcess(kPyMb); // Minimum Bias | |
52 | ||
53 | // Centre of mass energy | |
54 | genP->SetEnergyCMS(e_cms); // in GeV | |
55 | ||
56 | //for jet quenching with QPYTHIA | |
57 | if (fpythia == 1){ | |
a2af8c5e | 58 | genP->SetTune(103); //tune DW, standard choice for Q2 showers |
e66c7726 | 59 | genP->SetQuench(4); |
60 | genP->SetQhat(quench); | |
61 | } | |
62 | ||
63 | //for pyquen afterburner | |
64 | if (fpythia == 2){ | |
a2af8c5e | 65 | genP->SetTune(103); //tune DW, standard choice for Q2 showers |
e66c7726 | 66 | genP->SetQuench(2); |
67 | } | |
68 | ||
69 | return genP; | |
70 | } |