From 618ce654705de0249305cad03c0b53e631417571 Mon Sep 17 00:00:00 2001
From: Alberto Caliva <alberto.caliva@cern.ch>
Date: Tue, 3 Jun 2025 17:51:47 +0200
Subject: [PATCH] [PWGLF] added spin-isospin scaling factor and removed event
 selection

---
 .../ini/tests/GeneratorLF_deuteron_wigner.C   |  8 ++---
 .../generator_pythia8_deuteron_wigner.C       | 30 ++++++-------------
 2 files changed, 13 insertions(+), 25 deletions(-)

diff --git a/MC/config/PWGLF/ini/tests/GeneratorLF_deuteron_wigner.C b/MC/config/PWGLF/ini/tests/GeneratorLF_deuteron_wigner.C
index cf671fe9e..3cf153204 100644
--- a/MC/config/PWGLF/ini/tests/GeneratorLF_deuteron_wigner.C
+++ b/MC/config/PWGLF/ini/tests/GeneratorLF_deuteron_wigner.C
@@ -31,11 +31,11 @@ int External() {
   }
 
   if (nSelected == 0) {
-    std::cerr << "No event of interest\n";
-    return 1;
+    std::cout << "No events with deuterons found.\n";
+  } else {
+    std::cout << "Found " << nSelected << " events with deuterons\n";
   }
-
-  std::cout << "Found " << nSelected << " events with deuterons\n";
   return 0;
+
 }
 
diff --git a/MC/config/PWGLF/pythia8/generator_pythia8_deuteron_wigner.C b/MC/config/PWGLF/pythia8/generator_pythia8_deuteron_wigner.C
index 6bf7863d8..dce3499b4 100644
--- a/MC/config/PWGLF/pythia8/generator_pythia8_deuteron_wigner.C
+++ b/MC/config/PWGLF/pythia8/generator_pythia8_deuteron_wigner.C
@@ -46,35 +46,26 @@ public:
   ~GeneratorPythia8DeuteronWigner() override = default;
 
   bool Init() override {
-    addSubGenerator(0, "Pythia8 with (anti)deuterons formed via coalescence using the Wigner density formalism");
+    addSubGenerator(0, "Pythia8 events with (anti)deuterons formed via coalescence using the Wigner density formalism, provided the coalescence condition is fulfilled");
     return o2::eventgen::GeneratorPythia8::Init();
   }
 
 protected:
   bool generateEvent() override {
-    if (mGeneratedEvents % 100 == 0) {
-      LOG(info) << ">> Generating event " << mGeneratedEvents;
-    }
-
-    bool genOk = false;
-    int localCounter = 0;
-    while (!genOk) {
-      if (GeneratorPythia8::generateEvent()) {
-        genOk = selectEvent(mPythia.event);
-      }
-      localCounter++;
+    
+    if (GeneratorPythia8::generateEvent() && EventHasDeuteron(mPythia.event)) {
+      LOG(debug) << ">> A Deuteron was formed!";
     }
 
-    LOG(debug) << ">> Generation of event of interest successful after " << localCounter << " iterations";
     notifySubGenerator(0);
     ++mGeneratedEvents;
     return true;
   }
 
-  bool selectEvent(Pythia8::Event& event) {
+  bool EventHasDeuteron(Pythia8::Event& event) {
 
-    const double md = 1.87561294257; // Deuteron mass [GeV]
     bool deuteronIsFormed = false;
+    const double md = 1.87561294257; // Deuteron mass [GeV]
 
     std::vector<int> proton_ID, neutron_ID;
     std::vector<int> proton_status, neutron_status;
@@ -94,10 +85,6 @@ protected:
       }
     }
 
-    if (proton_ID.empty() || neutron_ID.empty()) {
-      return false;
-    }
-
     int radiusBin = mTwoDimCoalProbability->GetXaxis()->FindBin(mSourceRadius);
     TH1D* prob_vs_q = mTwoDimCoalProbability->ProjectionY("prob_vs_q", radiusBin, radiusBin, "E");
     prob_vs_q->SetDirectory(nullptr);
@@ -130,9 +117,10 @@ protected:
           continue;
         }
         double coalProb = prob_vs_q->GetBinContent(prob_vs_q->FindBin(deltaP));
-        double rnd = gRandom->Uniform(0.0, 1.0);
+        double rndCoalProb = gRandom->Uniform(0.0, 1.0);
+        double rndSpinIsospin = gRandom->Uniform(0.0, 1.0);
 
-        if (rnd < coalProb) {
+        if (rndCoalProb < coalProb && rndSpinIsospin < 3.0/8.0) {
           double energy = std::hypot(p.pAbs(), md);
           p.e(energy);
           int deuteronPDG = sign_p * 1000010020;