Add protection against skipped loopers

Author: jackal1-66

Generators/src/Generator.cxx

@@ -248,20 +248,26 @@ Bool_t
       LOG(error) << "Failed to generate loopers event";
       return kFALSE;
     }
-    if (mTPCLoopersGen->getNLoopers() == 0) {
+    const auto nCandidates = mTPCLoopersGen->getNLoopers();
+    if (nCandidates == 0) {
       LOG(warning) << "No loopers generated for this event";
       return kTRUE;
     }
     const auto& looperParticles = mTPCLoopersGen->importParticles();
+    const auto skippedLoopers = mTPCLoopersGen->getNSkipped();
     if (looperParticles.empty()) {
+      if (skippedLoopers == nCandidates) {
+        // all candidate loopers were dropped by the geometrical protection
+        LOG(debug) << "All " << skippedLoopers << " candidate loopers were outside the TPC active volume; none added for this event";
+        return kTRUE;
+      }
       LOG(error) << "Failed to import loopers particles";
       return kFALSE;
     }
     // Append the generated looper particles to the main particle list
     mParticles.insert(mParticles.end(), looperParticles.begin(), looperParticles.end());
 
     LOG(debug) << "Added " << looperParticles.size() << " looper particles";
-    const auto skippedLoopers = mTPCLoopersGen->getNSkipped();
     if (skippedLoopers > 0) {
       LOG(debug) << "Geometrical protection skipped " << skippedLoopers << " loopers outside the TPC active volume";
     }