From 704b321b65d8d3a3e8654e05cc0a431e20cedfe4 Mon Sep 17 00:00:00 2001
From: Marco Giacalone <mgiacalo@gmail.com>
Date: Thu, 3 Sep 2026 13:25:40 +0200
Subject: [PATCH] Add protection against skipped loopers

---
 Generators/src/Generator.cxx | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/Generators/src/Generator.cxx b/Generators/src/Generator.cxx
index 4e6f6dc91a723..7984f4f800206 100644
--- a/Generators/src/Generator.cxx
+++ b/Generators/src/Generator.cxx
@@ -248,12 +248,19 @@ 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;
     }
@@ -261,7 +268,6 @@ Bool_t
     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";
     }