Index: trunk/examples/sartreMain.cpp
===================================================================
--- trunk/examples/sartreMain.cpp	(revision 437)
+++ trunk/examples/sartreMain.cpp	(revision 438)
@@ -1,291 +1,297 @@
 //==============================================================================
 //  sartreMain.cpp
 //
 //  Copyright (C) 2010-2019 Tobias Toll and Thomas Ullrich
 //
 //  This file is part of Sartre.
 //
 //  This program is free software: you can redistribute it and/or modify
 //  it under the terms of the GNU General Public License as published by
 //  the Free Software Foundation.
 //  This program is distributed in the hope that it will be useful,
 //  but without any warranty; without even the implied warranty of
 //  merchantability or fitness for a particular purpose. See the
 //  GNU General Public License for more details.
 //  You should have received a copy of the GNU General Public License
 //  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 //
 //  Author: Thomas Ullrich
 //  Last update:
 //  $Date$
 //  $Author$
 //==============================================================================
 //
-//  Example main program. Use to get started.
+//  Example main program. Useful to get started and easy to modify to fit
+//  the user need. Data are stored in a simple but complete Root TTree.
 //
 //==============================================================================
 #include <iostream>
 #include <cmath>
 #include "TTree.h"
 #include "TFile.h"
-#include "Sartre.h"
-#include "DipoleModelParameters.h"
 #include "TGenPhaseSpace.h"
-#include "Settings.h"
 #include "TH1D.h"
 #include "TROOT.h"
 #include "TLorentzVector.h"
 #include "TClonesArray.h"
+#include "Sartre.h"
+#include "Settings.h"
+#include "DipoleModelParameters.h"
+#include "TwoBodyVectorMesonDecay.h"
 
 #define PR(x) cout << #x << " = " << (x) << endl;
 
 using namespace std;
 
 struct rootSartreEvent {
     double t;
     double Q2;
     double x;
     double s;
     double y;
     double W;
     double xpom;
     int    iEvent;
     int    pol;      // 0=transverse or 1=longitudinal
     int    dmode;    // 0=coherent, 1=Incoherent
 };
 
 rootSartreEvent myRootSartreEvent;
 void randomlyReverseBeams(Event* );  // for UPC mode
 
 int main(int argc, char *argv[])
 {
     //
     //  Check command line arguments
     //
     if (! (argc == 2 || argc == 3) ) {
         cout << "Usage:  " << argv[0] << " runcard [rootfile]" << endl;
         return 2;
     }
     string runcard = argv[1];
     
     //
     //  Create the generator and initialize it.
     //  Once initialized you cannot (should not) change
     //  the settings w/o re-initialing sartre.
     //
     Sartre sartre;
     bool ok = sartre.init(runcard);
     if (!ok) {
-        cerr << "Initialization of sartre failed." << endl;
+        cerr << "Error: Initialization of sartre failed." << endl;
         return 1;
     }
 
     EventGeneratorSettings* settings = sartre.runSettings();
 
     //
     //  ROOT file
     //  Use the one from command line unless not given
     //  in which case the one in the runcard is used.
     //
     string rootfile;
     if (argc == 3) {
         rootfile = argv[2];
         settings->setRootfile(argv[2]);
     }
     else
         rootfile = settings->rootfile();
  
     //
     //  Print out all Sartre settings
     //
     settings->list();
     
     TFile *hfile = 0;
     if (rootfile.size()) {
         hfile  = new TFile(rootfile.c_str(),"RECREATE");
         cout << "ROOT file is '" <<  rootfile.c_str() << "'." << endl;
     }
     
     //
     //  Setup ROOT tree
     //
     TLorentzVector *eIn = new TLorentzVector;
     TLorentzVector *pIn = new TLorentzVector;
     TLorentzVector *vm = new TLorentzVector;
     TLorentzVector *eOut = new TLorentzVector;
     TLorentzVector *pOut = new TLorentzVector;
     TLorentzVector *gamma = new TLorentzVector;
     TLorentzVector *vmDaughter1 = new TLorentzVector;
     TLorentzVector *vmDaughter2 = new TLorentzVector;
     
     TClonesArray protons("TLorentzVector");
     TClonesArray neutrons("TLorentzVector");
     TClonesArray remnants("TLorentzVector");
     
     TTree tree("tree","sartre");
     tree.Branch("event", &myRootSartreEvent.t,
                 "t/D:Q2/D:x/D:s/D:y/D:W/D:xpom/D:iEvent/I:pol/I:dmode/I");
     tree.Branch("eIn",  "TLorentzVector", &eIn, 32000, 0);
     tree.Branch("pIn",  "TLorentzVector", &pIn, 32000, 0);
     tree.Branch("vm",   "TLorentzVector", &vm, 32000, 0);
     tree.Branch("eOut", "TLorentzVector", &eOut, 32000, 0);
     tree.Branch("pOut", "TLorentzVector", &pOut, 32000, 0);
     tree.Branch("gamma","TLorentzVector", &gamma, 32000, 0);
     tree.Branch("vmDaughter1", "TLorentzVector", &vmDaughter1, 32000, 0);
     tree.Branch("vmDaughter2", "TLorentzVector", &vmDaughter2, 32000, 0);
     
     if(settings->enableNuclearBreakup()){
         tree.Branch("protons", &protons);
         tree.Branch("neutrons", &neutrons);
         tree.Branch("nuclearRemnants", &remnants);
     }
     
     //
     //  Prepare event generation
     //
-    TGenPhaseSpace decay;  // for VM decays
-    int daughterID = settings->userInt();
-    double daughterMasses[2] = {0, 0};
+    TwoBodyVectorMesonDecay decayEngine;
+    pair<TLorentzVector, TLorentzVector> daughters;
+    int  daughterID = settings->userInt();
     bool doPerformDecay = false;
+    
     if (daughterID && settings->vectorMesonId() != 22) {
-        doPerformDecay = true;
-        daughterMasses[0] = settings->lookupPDG(daughterID)->Mass();
-        daughterMasses[1] = settings->lookupPDG(-daughterID)->Mass();
-        cout << "Will decay vector meson: ";
-        cout << settings->lookupPDG(settings->vectorMesonId())->GetName();
-        cout << " -> ";
-        cout << settings->lookupPDG(daughterID)->GetName();
-        cout << " ";
-        cout << settings->lookupPDG(-daughterID)->GetName();
-        cout << endl;
+        if (abs(daughterID) == 11 || abs(daughterID) == 13 ||
+            abs(daughterID) == 211 || abs(daughterID) == 321) {
+            doPerformDecay = true;
+            cout << "Will decay vector meson: ";
+            cout << settings->lookupPDG(settings->vectorMesonId())->GetName();
+            cout << " -> ";
+            cout << settings->lookupPDG(daughterID)->GetName();
+            cout << " ";
+            cout << settings->lookupPDG(-daughterID)->GetName();
+            cout << endl;
+        }
+        else {
+            cerr << "Error: Cannot decay vector meson to daughters with ID=" << daughterID << "." << endl;
+            return 1;
+        }
     }
     
+    //
+    //  Events and how often to show status
+    //
     int nPrint;
     if (settings->timesToShow())
         nPrint = settings->numberOfEvents()/settings->timesToShow();
     else
         nPrint = 0;
     
     unsigned long maxEvents = settings->numberOfEvents();
     
     cout << "Generating " << maxEvents << " events." << endl << endl;
     
     //
     //  Event generation
     //
     for (unsigned long iEvent = 0; iEvent < maxEvents; iEvent++) {
+        
         //
         //  Generate one event
         //
         Event *event = sartre.generateEvent();
         if (nPrint && (iEvent+1)%nPrint == 0 && iEvent != 0) {
             cout << "processed " << iEvent+1 << " events" << endl;
         }
         
         //
         //  If Sartre is run in UPC mode, half of the events needs to be
         //  rotated around and axis perpendicular to z:
         //
-        if(settings->UPC() and settings->A()==settings->UPCA()){
+        if(settings->UPC() && settings->A() == settings->UPCA()){
             randomlyReverseBeams(event);
         }
         
         //
         //  Print out (here only for the first few events)
         //
         if (iEvent < 10) event->list();
         
         //
         //  Fill ROOT tree
         //
         myRootSartreEvent.iEvent = event->eventNumber;
         myRootSartreEvent.t = event->t;
         myRootSartreEvent.Q2 = event->Q2;
         myRootSartreEvent.x = event->x;
         myRootSartreEvent.y = event->y;
         myRootSartreEvent.s = event->s;
         myRootSartreEvent.W = event->W;
         myRootSartreEvent.xpom = event->xpom;
         myRootSartreEvent.pol = event->polarization == transverse ? 0 : 1;
         myRootSartreEvent.dmode = event->diffractiveMode == coherent ? 0 : 1;
         eIn     = &event->particles[0].p;
         pIn     = &event->particles[1].p;
         eOut    = &event->particles[2].p;
         pOut    = &event->particles[6].p;
         vm      = &event->particles[4].p;
         gamma   = &event->particles[3].p;
         
         //If the event is incoherent, and nuclear breakup is enabled, fill the remnants to the tree
         if(settings->enableNuclearBreakup() and event->diffractiveMode == incoherent){
             protons.Clear();
             neutrons.Clear();
             remnants.Clear();
             for(unsigned int iParticle=7; iParticle < event->particles.size(); iParticle++){
                 if(event->particles[iParticle].status == 1) {  // Final-state particle
                     const Particle& particle = event->particles[iParticle];
                     switch (abs(particle.pdgId)) {
                         case 2212:  // (Anti-)proton
                             new(protons[protons.GetEntries()]) TLorentzVector(particle.p);
                             break;
                         case 2112:  // (Anti-)neutron
                             new(neutrons[neutrons.GetEntries()]) TLorentzVector(particle.p);
                             break;
                         default:  // Any other remnant
                             new(remnants[remnants.GetEntries()]) TLorentzVector(particle.p);
                             break;
                     }  // switch
                 }  // if
             }  // for
         }  // if
         
         //
-        // Decay the vector meson and fill the decay roducts in the tree:
+        //   Decay the vector meson and fill the decay products in the tree.
+        //   For the decay we use the version that is sensitive to the
+        //   polarization of the virtual photon (on a statistical basis).
         //
-        if(doPerformDecay) {
-            if( decay.SetDecay(*vm, 2, daughterMasses) ){
-                double weight = decay.Generate(); // weight is always 1 here
-                if ( (weight-1) > FLT_EPSILON) {
-                    cout << "sartreMain: Warning weight != 1, weight = " << weight << endl;
-                }
-                vmDaughter1 = decay.GetDecay(0);
-                vmDaughter2 = decay.GetDecay(1);
-            }
-            else {
-                cout << "sartreMain: Warning: Kinematics of Vector Meson does not allow decay!" << endl;
-            }
+        if (doPerformDecay) {
+            daughters = decayEngine.decayVectorMeson(*vm, *event, daughterID);
+            vmDaughter1 = &daughters.first;
+            vmDaughter2 = &daughters.second;
         }
         
         tree.Fill();
     }
     cout << "All events processed\n" << endl;
     
     //
     //  That's it, finish up
     //
     double totalCS=sartre.totalCrossSection();
     TH1D* histoForCSandNumberOfEvents = new TH1D("histoForCSandNumberOfEvents", "Cross-section and Number of Events", 2, 0., 1.);
     histoForCSandNumberOfEvents->SetBinContent(1, totalCS);
     histoForCSandNumberOfEvents->SetBinContent(2, maxEvents);
     
     double runTime = sartre.runTime();
     hfile->Write();
     cout << rootfile.c_str() << " written." << endl;
     cout << "Total cross-section: " << totalCS << " nb" << endl;
     sartre.listStatus();   
     cout << "CPU Time/event: " << 1000*runTime/maxEvents << " msec/evt" << endl;   
     
     return 0;   
 }   
 
 // UPC only
-void randomlyReverseBeams(Event* myEvent) {
-    
+void randomlyReverseBeams(Event* myEvent)
+{
     TRandom3 *random = EventGeneratorSettings::randomGenerator();
     
     if(random->Uniform(1) > 0.5){
         for(unsigned int i=0; i<myEvent->particles.size(); i++)
             myEvent->particles.at(i).p.RotateX(M_PI);
     }
 }