diff --git a/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/CalibrationDataInterface/CalibrationDataContainer.h b/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/CalibrationDataInterface/CalibrationDataContainer.h
index 7f29c0f163d0d3a49365cd926fbebc0af2e9e49d..4fbee75c1e11cbc6b5cf9513ba17a5923201edc0 100644
--- a/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/CalibrationDataInterface/CalibrationDataContainer.h
+++ b/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/CalibrationDataInterface/CalibrationDataContainer.h
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2002-2022 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
 */
 
 ///////////////////////////////////////////////////////////////////
@@ -355,7 +355,7 @@ namespace Analysis {
     void setMappedVariables(const std::vector<std::string>& variables);
 
     /** List which variables get mapped onto a single histogram axis */
-    std::vector<std::string> getMappedVariables() const;
+    const std::vector<std::string>& getMappedVariables() const;
 
     /** Retrieve the bin boundaries for the specified variable type (which should be a CalibrationParametrization enum).
 	An empty vector will be returned if the specified variable is not actually used. */
diff --git a/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/Root/CDIReader.cxx b/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/Root/CDIReader.cxx
index 71776ecc1d9a62d4a3b5f84e3dcebcc5e82763b1..41dffc9784052a950a71d6fec9ba90befc995973 100644
--- a/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/Root/CDIReader.cxx
+++ b/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/Root/CDIReader.cxx
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2002-2023 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
 */
 
 //////////////////////////////////////////////////////////////////////
@@ -224,7 +224,7 @@ bool Analysis::CDIReader::checkConfig(const std::string& tagger, const std::stri
         if (verbose) std::cout << " Your configuration looks good! Available labels are : " << std::endl;
         if (verbose) printMetadata(tagger_ind, jetcoll_ind, wp_ind, -1);
         // construct vector of labels
-        for(std::string flavour_label : m_metadata[tagger][jetcoll][wp]["labels"]){
+        for(const std::string& flavour_label : m_metadata[tagger][jetcoll][wp]["labels"]){
           m_label_vec.push_back(flavour_label);
         }
         // sort the vector of labels
@@ -303,7 +303,7 @@ std::vector<std::string> Analysis::CDIReader::getLabels(const std::string& tagge
   } else if(m_workingpoints.find(workingpoint) == m_workingpoints.end()){
     std::cout << " The working point [" << workingpoint << "] doesn't exist in " << tagger << "/" << jetcollection <<  " this CDI file!" << std::endl;
   } else {
-    for (std::string label : m_metadata[tagger][jetcollection][workingpoint]["labels"]){
+    for (const std::string& label : m_metadata[tagger][jetcollection][workingpoint]["labels"]){
       labels.push_back(label);
     }
   }
diff --git a/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/Root/CalibrationDataContainer.cxx b/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/Root/CalibrationDataContainer.cxx
index 42a7dd0eb5d8d136535a35ab0ee437e31aef7106..9405a8964e301cd27cbe33d40de41b1e198579a3 100644
--- a/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/Root/CalibrationDataContainer.cxx
+++ b/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/Root/CalibrationDataContainer.cxx
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2002-2023 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
 */
 
 
@@ -1271,7 +1271,7 @@ CalibrationDataMappedHistogramContainer::setMappedVariables(const std::vector<st
 }
 
 //________________________________________________________________________________
-std::vector<std::string>
+const std::vector<std::string>&
 CalibrationDataMappedHistogramContainer::getMappedVariables() const
 {
   // List which variables get mapped onto a single histogram axis
diff --git a/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/src/CalibrationDataUpdater.cxx b/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/src/CalibrationDataUpdater.cxx
index e03ac3e5db273de83883e3a658cceb425d1204dd..b0a17c2651b5d596b3f9b5eda772f3f86deebd32 100644
--- a/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/src/CalibrationDataUpdater.cxx
+++ b/PhysicsAnalysis/JetTagging/JetTagPerformanceCalibration/CalibrationDataInterface/src/CalibrationDataUpdater.cxx
@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2002-2022 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
 */
 
 ///////////////////////////////////////////////////////////////////
@@ -63,7 +63,7 @@ StatusCode Analysis::CalibrationDataUpdater::initialize()
     return StatusCode::FAILURE;
   }
 
-  for (auto itname : m_paramNames){
+  for (const std::string& itname : m_paramNames){
     string to = *itname;
     // 1. determine whether to insert new results
     if (newInput) {