fix issues found with performance-for-range-copy clang-tidy check (#2833)

1 files changed, 1 insertions, 1 deletions

diff --git a/Source/Particles/Collision/BackgroundMCCCollision.cpp b/Source/Particles/Collision/BackgroundMCCCollision.cpp
index b051f8e22..7086ae80f 100644
--- a/Source/Particles/Collision/BackgroundMCCCollision.cpp
+++ b/Source/Particles/Collision/BackgroundMCCCollision.cpp
@@ -44,7 +44,7 @@ BackgroundMCCCollision::BackgroundMCCCollision (std::string const collision_name
 
     // create a vector of MCCProcess objects from each scattering
     // process name
-    for (auto scattering_process : scattering_process_names) {
+    for (const auto& scattering_process : scattering_process_names) {
         std::string kw_cross_section = scattering_process + "_cross_section";
         std::string cross_section_file;
         pp_collision_name.query(kw_cross_section.c_str(), cross_section_file);