diff --git a/DataFormats/simulation/include/SimulationDataFormat/MCEventHeader.h b/DataFormats/simulation/include/SimulationDataFormat/MCEventHeader.h
index 3af79fb360737..2a0338828ac17 100644
--- a/DataFormats/simulation/include/SimulationDataFormat/MCEventHeader.h
+++ b/DataFormats/simulation/include/SimulationDataFormat/MCEventHeader.h
@@ -74,6 +74,12 @@ class MCEventHeader : public FairMCEventHeader
     return ref;
   };
 
+  /// prints a summary of info keys/types attached to this header
+  void printInfo() const
+  {
+    mEventInfo.print();
+  }
+
   /** methods **/
   virtual void Reset();
 
diff --git a/Generators/src/GeneratorPythia8.cxx b/Generators/src/GeneratorPythia8.cxx
index 751002d132c3e..54a4a4e6fd0d8 100644
--- a/Generators/src/GeneratorPythia8.cxx
+++ b/Generators/src/GeneratorPythia8.cxx
@@ -196,15 +196,37 @@ void GeneratorPythia8::updateHeader(o2::dataformats::MCEventHeader* eventHeader)
 {
   /** update header **/
 
+  eventHeader->putInfo<std::string>("generator", "pythia8");
+  eventHeader->putInfo<int>("version", PYTHIA_VERSION_INTEGER);
+
 #if PYTHIA_VERSION_INTEGER < 8300
   auto hiinfo = mPythia.info.hiinfo;
 #else
   auto hiinfo = mPythia.info.hiInfo;
 #endif
 
-  /** set impact parameter if in heavy-ion mode **/
   if (hiinfo) {
+    /** set impact parameter **/
     eventHeader->SetB(hiinfo->b());
+    eventHeader->putInfo<double>("Bimpact", hiinfo->b());
+    /** set Ncoll, Npart and Nremn **/
+    int nColl, nPart;
+    int nPartProtonProj, nPartNeutronProj, nPartProtonTarg, nPartNeutronTarg;
+    int nRemnProtonProj, nRemnNeutronProj, nRemnProtonTarg, nRemnNeutronTarg;
+    getNcoll(nColl);
+    getNpart(nPart);
+    getNpart(nPartProtonProj, nPartNeutronProj, nPartProtonTarg, nPartNeutronTarg);
+    getNremn(nRemnProtonProj, nRemnNeutronProj, nRemnProtonTarg, nRemnNeutronTarg);
+    eventHeader->putInfo<int>("Ncoll", nColl);
+    eventHeader->putInfo<int>("Npart", nPart);
+    eventHeader->putInfo<int>("Npart_proj_p", nPartProtonProj);
+    eventHeader->putInfo<int>("Npart_proj_n", nPartNeutronProj);
+    eventHeader->putInfo<int>("Npart_targ_p", nPartProtonTarg);
+    eventHeader->putInfo<int>("Npart_targ_n", nPartNeutronTarg);
+    eventHeader->putInfo<int>("Nremn_proj_p", nRemnProtonProj);
+    eventHeader->putInfo<int>("Nremn_proj_n", nRemnNeutronProj);
+    eventHeader->putInfo<int>("Nremn_targ_p", nRemnProtonTarg);
+    eventHeader->putInfo<int>("Nremn_targ_n", nRemnNeutronTarg);
   }
 }
 
diff --git a/run/O2HitMerger.h b/run/O2HitMerger.h
index adc652bf03dc2..2b90119ea2715 100644
--- a/run/O2HitMerger.h
+++ b/run/O2HitMerger.h
@@ -551,7 +551,7 @@ class O2HitMerger : public FairMQDevice
     std::vector<int> nprimaries;   // collecting primary particles in each subevent
     std::vector<int> nsubevents;   // collecting of subevent numbers
 
-    std::unique_ptr<o2::dataformats::MCEventHeader> eventheader; // The event header
+    o2::dataformats::MCEventHeader* eventheader = nullptr; // The event header
 
     // the MC labels (trackID) for hits
     o2::data::SubEventInfo* info = nullptr;
@@ -562,9 +562,9 @@ class O2HitMerger : public FairMQDevice
       trackoffsets.emplace_back(info->npersistenttracks);
       nprimaries.emplace_back(info->nprimarytracks);
       nsubevents.emplace_back(info->part);
+      info->mMCEventHeader.printInfo();
       if (eventheader == nullptr) {
-        eventheader = std::unique_ptr<dataformats::MCEventHeader>(
-          new dataformats::MCEventHeader(info->mMCEventHeader));
+        eventheader = &info->mMCEventHeader;
       } else {
         eventheader->getMCEventStats().add(info->mMCEventHeader.getMCEventStats());
       }
@@ -580,9 +580,9 @@ class O2HitMerger : public FairMQDevice
     }
 
     // put the event headers into the new TTree
-    o2::dataformats::MCEventHeader* headerptr = eventheader.get();
-    auto headerbr = o2::base::getOrMakeBranch(*mOutTree, "MCEventHeader.", &headerptr);
-    headerbr->SetAddress(&headerptr);
+    eventheader->printInfo();
+    auto headerbr = o2::base::getOrMakeBranch(*mOutTree, "MCEventHeader.", &eventheader);
+    headerbr->SetAddress(&eventheader);
     headerbr->Fill();
     headerbr->ResetAddress();