1 // Author: Leticia Cunqueiro
4 //if fpythia==1, quenched pythia (qpythia) is configured.
5 //if fpythia==2, pyquen afterburner applyed
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.
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.
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
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)
28 //Add Pythia generator: pt-hard bin or min bias
30 gSystem->Load("liblhapdf.so");
32 return CreatePythia6Gen(e_cms, ptHardMin, ptHardMax, fpythia, quench);
35 AliGenerator* CreatePythia6Gen(Float_t e_cms, Int_t ptHardMin, Int_t ptHardMax, Int_t fpythia, Double_t quench) {
37 gSystem->Load("libqpythia.so");
38 gSystem->Load("libEGPythia6.so");
39 gSystem->Load("libAliPythia6.so");
41 AliGenPythia* genP = new AliGenPythia(1);
43 // vertex position and smearing
44 genP->SetVertexSmear(kPerEvent);
46 // charm, beauty, charm_unforced, beauty_unforced, jpsi, jpsi_chi, mb
48 genP->SetProcess(kPyJets);
49 genP->SetPtHard((float)ptHardMin,(float)ptHardMax);
51 genP->SetProcess(kPyMb); // Minimum Bias
53 // Centre of mass energy
54 genP->SetEnergyCMS(e_cms); // in GeV
56 //for jet quenching with QPYTHIA
58 genP->SetTune(103); //tune DW, standard choice for Q2 showers
60 genP->SetQhat(quench);
63 //for pyquen afterburner
65 genP->SetTune(103); //tune DW, standard choice for Q2 showers