added references to const in for loop

Author: ppoava

Common/Tasks/qaMuon.cxx

@@ -1263,7 +1263,7 @@ struct muonQa {
 
       // outer loop over muon tracks
       auto muonCollision1 = muons.sliceBy(fwdtracksPerCollision, collisionInfo1.globalIndex);
-      for (const auto muon1 : muonCollision1) {
+      for (const auto& muon1 : muonCollision1) {
 
         if (muon1.trackType() <= 2) {
           continue;
@@ -1284,7 +1284,7 @@ struct muonQa {
 
           // inner loop over muon tracks
           auto muonCollision2 = muons.sliceBy(fwdtracksPerCollision, collisionInfo2.globalIndex);
-          for (const auto muon2 : muonCollision2) {
+          for (const auto& muon2 : muonCollision2) {
             if (muon2.trackType() <= 2) {
               continue;
             }
@@ -1306,7 +1306,7 @@ struct muonQa {
 
       // outer loop over global muon tracks
       auto muonCollision1 = muons.sliceBy(fwdtracksPerCollision, collisionInfo1.globalIndex);
-      for (const auto muon1 : muonCollision1) {
+      for (const auto& muon1 : muonCollision1) {
 
         if (muon1.trackType() <= 2) {
           continue;
@@ -1331,7 +1331,7 @@ struct muonQa {
 
           // outer loop over global muon tracks
           auto muonCollision2 = muons.sliceBy(fwdtracksPerCollision, collisionInfo2.globalIndex);
-          for (const auto muon2 : muonCollision2) {
+          for (const auto& muon2 : muonCollision2) {
 
             if (muon2.trackType() <= 2) {
               continue;