PWG2/FLOW/AliFlowCommon/AliFlowLYZEventPlane.cxx

   1 /*************************************************************************
   2 * Copyright(c) 1998-2008, ALICE Experiment at CERN, All rights reserved. *
   3 *                                                                        *
   4 * Author: The ALICE Off-line Project.                                    *
   5 * Contributors are mentioned in the code where appropriate.              *
   6 *                                                                        *
   7 * Permission to use, copy, modify and distribute this software and its   *
   8 * documentation strictly for non-commercial purposes is hereby granted   *
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  10 * copies and that both the copyright notice and this permission notice   *
  11 * appear in the supporting documentation. The authors make no claims     *
  12 * about the suitability of this software for any purpose. It is          *
  13 * provided "as is" without express or implied warranty.                  *
  14 **************************************************************************/
  15
  16 #define AliFlowAnalysisWithLYZEventPlane_cxx
  17
  18 // AliFlowLYZEventPlane:
  19 //
  20 // Class to calculate the event plane and event weight from the LYZ method
  21 // It needs input from the standard LYZ first and second run
  22 // author: N. van der Kolk (kolk@nikhef.nl)
  23
  24 #include "Riostream.h"
  25 #include "TProfile.h"
  26 #include "TFile.h"
  27 #include "TComplex.h"
  28 #include "TList.h"
  29
  30 #include "AliFlowVector.h"
  31 #include "AliFlowLYZConstants.h"
  32 #include "AliFlowEventSimple.h"
  33 #include "AliFlowLYZEventPlane.h"
  34
  35 class AliFlowTrackSimple;
  36
  37 ClassImp(AliFlowLYZEventPlane)
  38
  39   //-----------------------------------------------------------------------
  40
  41 AliFlowLYZEventPlane::AliFlowLYZEventPlane():
  42   fSecondRunList(0),
  43   fWR(0),
  44   fPsi(0),
  45   fSecondReDtheta(0),
  46   fSecondImDtheta(0),
  47   fFirstr0theta(0)
  48 {
  49   // Constructor.
  50
  51 }
  52 //-----------------------------------------------------------------------
  53
  54
  55 AliFlowLYZEventPlane::~AliFlowLYZEventPlane()
  56 {
  57   //destructor
  58   delete fSecondRunList;
  59 }
  60
  61
  62 //-----------------------------------------------------------------------
  63 void AliFlowLYZEventPlane::Init()
  64 {
  65   //Declare histograms & get input files
  66   cout<<"---Lee Yang Zeros Event Plane Method---"<<endl;
  67
  68   //input histograms
  69   if (fSecondRunList) {
  70     fSecondReDtheta = (TProfile*)fSecondRunList->FindObject("Second_FlowPro_ReDtheta_LYZSUM");
  71     fSecondImDtheta = (TProfile*)fSecondRunList->FindObject("Second_FlowPro_ImDtheta_LYZSUM");
  72     fFirstr0theta   = (TProfile*)fSecondRunList->FindObject("First_FlowPro_r0theta_LYZSUM");
  73
  74     //warnings
  75     if (!fSecondReDtheta) {cout<<"fSecondReDtheta is NULL!"<<endl; }
  76     if (!fSecondImDtheta) {cout<<"fSecondImDtheta is NULL!"<<endl; }
  77     if (!fFirstr0theta)   {cout<<"fFirstr0theta is NULL!"<<endl; }
  78   }
  79
  80
  81 }
  82
  83 //-----------------------------------------------------------------------
  84 void AliFlowLYZEventPlane::CalculateRPandW(AliFlowVector aQ)
  85 {
  86   //declare variables
  87   Int_t iNtheta = AliFlowLYZConstants::GetMaster()->GetNtheta();
  88   Double_t dCosTerm = 0;
  89   Double_t dSinTerm = 0;
  90   TComplex cDtheta;
  91   TComplex cRatio;
  92
  93   if (aQ.Mod()==0.) { cout<<"Q vector is NULL"<<endl; }
  94   else {
  95     for (Int_t theta=0;theta<iNtheta;theta++)   {
  96       Double_t dTheta = ((float)theta/iNtheta)*TMath::Pi()/2;
  97       //Calculate Qtheta
  98       Double_t dQtheta = aQ.X()*cos(2*dTheta)+aQ.Y()*sin(2*dTheta);  //get Qtheta from Q vector
  99
 100       //get R0
 101       Double_t dR0 = fFirstr0theta->GetBinContent(theta+1);
 102       //cerr<<"dR0 = "<<dR0<<endl;
 103
 104       //get Dtheta
 105       Double_t dReDtheta = fSecondReDtheta->GetBinContent(theta+1);
 106       //cerr<<"dReDtheta = "<<dReDtheta<<endl;
 107       Double_t dImDtheta = fSecondImDtheta->GetBinContent(theta+1);
 108       //cerr<<"dImDtheta = "<<dImDtheta<<endl;
 109       cDtheta(dReDtheta,dImDtheta);
 110
 111       TComplex cExpo(0.,dR0*dQtheta);                  //Complex number: 0 +(i r0 Qtheta)
 112       if (cDtheta.Rho()!=0.) { cRatio =(TComplex::Exp(cExpo))/cDtheta; } //(e^(i r0 Qtheta))/Dtheta
 113       else { cRatio(0.,0.); }
 114
 115       //sum over theta
 116       dCosTerm += cRatio.Re() * TMath::Cos(2*dTheta);    //Re{(e^(i r0 Qtheta))/Dtheta } cos(2 theta)
 117       dSinTerm += cRatio.Re() * TMath::Sin(2*dTheta);    //Re{(e^(i r0 Qtheta))/Dtheta } sin(2 theta)
 118
 119     }//loop over theta
 120
 121     //average over theta
 122     dCosTerm /= iNtheta;
 123     dSinTerm /= iNtheta;
 124     //cerr<<"cosTerm & sinTerm are: "<<dCosTerm<<" & "<<dSinTerm<<endl;
 125
 126     //calculate fWR
 127     fWR = TMath::Sqrt(dCosTerm*dCosTerm + dSinTerm*dSinTerm);
 128
 129     //calculate fRP
 130     fPsi = 0.5*TMath::ATan2(dSinTerm,dCosTerm);   //takes care of the signs correctly!
 131     if (fPsi < 0.) { fPsi += TMath::Pi(); }       //to shift distribution from (-pi/2 to pi/2) to (0 to pi)
 132   }
 133
 134 }
 135