diff --git a/Simulation/DetSimMixing/src/BackgroundLoader.hh b/Simulation/DetSimMixing/src/BackgroundLoader.hh
index 6839ec53215523ae09148156ca6a5ec65e108034..f67b5b860ffc61e3fb67ad8e1d160063e44b261f 100644
--- a/Simulation/DetSimMixing/src/BackgroundLoader.hh
+++ b/Simulation/DetSimMixing/src/BackgroundLoader.hh
@@ -64,10 +64,10 @@ public:
                 continue;
             }
 
-            std::cout << "Collection: " << name 
-                      << ", index: " << colidx 
-                      << ", time window: " << time_window << " ns"
-                      << ", current time: " << current_time_in_ns;
+            // std::cout << "Collection: " << name 
+            //           << ", index: " << colidx 
+            //           << ", time window: " << time_window << " ns"
+            //           << ", current time: " << current_time_in_ns;
 
             // debug only. don't create any hits.
             // conclusion: no memory leakage in the above code.
@@ -137,7 +137,7 @@ public:
                 continue;
             }
 
-            std::cout << ", counter: " << counter << std::endl;
+            // std::cout << ", counter: " << counter << std::endl;
 
         }
 
diff --git a/Simulation/DetSimMixing/src/DetSimMixingAlg.cc b/Simulation/DetSimMixing/src/DetSimMixingAlg.cc
index cd0e030fbed29ee5fff773ce49475a7b4072ee77..2c6c7ba7d9262f8920f38b14a972b4f7c42c657c 100644
--- a/Simulation/DetSimMixing/src/DetSimMixingAlg.cc
+++ b/Simulation/DetSimMixing/src/DetSimMixingAlg.cc
@@ -73,7 +73,7 @@ StatusCode DetSimMixingAlg::initialize() {
         m_trackerColMap[name_col] = col;
 
         auto sig_col = new DataHandle<edm4hep::SimTrackerHitCollection>(name_col, Gaudi::DataHandle::Reader, this);
-        m_sig_trackerColMap[name_col] = col;
+        m_sig_trackerColMap[name_col] = sig_col;
         
     }
 
@@ -308,6 +308,9 @@ StatusCode DetSimMixingAlg::execute() {
                 newhit.setQuality(oldhit.getQuality());
                 newhit.setPosition(oldhit.getPosition());
                 newhit.setMomentum(oldhit.getMomentum());
+
+                // associate MC particle for signal
+                newhit.setMCParticle(oldhit.getMCParticle());
             }
 
         } else if (bkg_evt.calorimeter_hits.count(colidx)) {