diff --git a/benchmarks/dvmp/analysis/dvmp.h b/benchmarks/dvmp/analysis/dvmp.h
index bf542109d98992f61b4f780e5e7b2b32bcda27b1..65079e41d5641a77140a7f9f0c70d9ccfd599f7a 100644
--- a/benchmarks/dvmp/analysis/dvmp.h
+++ b/benchmarks/dvmp/analysis/dvmp.h
@@ -199,7 +199,7 @@ namespace util {
     ROOT::Math::PxPyPzMVector q(parts[0] - parts[2]);
     ROOT::Math::PxPyPzMVector P(parts[1]);
     ROOT::Math::PxPyPzMVector Delta(parts[3] - parts[1]);//jpsi->l l' gamma, ignore gamma
-    ROOT::Math::PxPyPzMVector Delta_prime(parts[0] - parts[2] - parts[5] - parts[6]);//exclude gamma radiation in jpsi decay
+    ROOT::Math::PxPyPzMVector Delta_prime(parts[0] - parts[2] - parts[4]);//exclude gamma radiation in jpsi decay
     
     double    nu         = q.Dot(P) / P.mass();
     double    Q2         = -q.Dot(q);