From 460d8fa62499186c8994f95b843d04e344f132fe Mon Sep 17 00:00:00 2001
From: Vladimir <Vladimir.Ivantchenko@cern.ch>
Date: Sun, 3 Dec 2023 13:33:47 +0100
Subject: [PATCH] provide simulation of ZDC

---
 SimG4Core/Application/interface/SteppingAction.h | 1 +
 SimG4Core/Application/src/SteppingAction.cc      | 7 +++++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/SimG4Core/Application/interface/SteppingAction.h b/SimG4Core/Application/interface/SteppingAction.h
index e4169361854d7..8fbe310ce98bf 100644
--- a/SimG4Core/Application/interface/SteppingAction.h
+++ b/SimG4Core/Application/interface/SteppingAction.h
@@ -50,6 +50,7 @@ class SteppingAction : public G4UserSteppingAction {
   EventAction* eventAction_;
   const G4VPhysicalVolume *tracker, *calo;
   const CMSSteppingVerbose* steppingVerbose;
+  const G4LogicalVolume* m_CMStoZDC{nullptr};
   double theCriticalEnergyForVacuum;
   double theCriticalDensity;
   double maxTrackTime;
diff --git a/SimG4Core/Application/src/SteppingAction.cc b/SimG4Core/Application/src/SteppingAction.cc
index d444995de890b..6857c928d04dc 100644
--- a/SimG4Core/Application/src/SteppingAction.cc
+++ b/SimG4Core/Application/src/SteppingAction.cc
@@ -151,13 +151,13 @@ void SteppingAction::UserSteppingAction(const G4Step* aStep) {
   }
 
   // check G4Region
-  if (sAlive == tstat) {
+  if (sAlive == tstat || sVeryForward == tstat) {
     // next logical volume and next region
     const G4LogicalVolume* lv = postStep->GetPhysicalVolume()->GetLogicalVolume();
     const G4Region* theRegion = lv->GetRegion();
 
     // kill in dead regions
-    if (isInsideDeadRegion(theRegion))
+    if (lv != m_CMStoZDC && isInsideDeadRegion(theRegion))
       tstat = sDeadRegion;
 
     // kill out of time
@@ -245,6 +245,9 @@ bool SteppingAction::initPointer() {
     ekinVolumes.resize(numberEkins, nullptr);
     for (auto const& lvcite : *lvs) {
       const G4String& lvname = lvcite->GetName();
+      if (lvname == "CMStoZDC") {
+	m_CMStoZDC = lvcite;
+      }
       for (unsigned int i = 0; i < numberEkins; ++i) {
         if (lvname == (G4String)(ekinNames[i])) {
           ekinVolumes[i] = lvcite;