diff --git a/benchmarks/imaging_ecal/scripts/draw_cluster.py b/benchmarks/imaging_ecal/scripts/draw_cluster.py
index 88f338d0befa96e45b6a16e4754e69d1cbfee2f3..25974ee9c4f9185a3b272423828411f441334826 100644
--- a/benchmarks/imaging_ecal/scripts/draw_cluster.py
+++ b/benchmarks/imaging_ecal/scripts/draw_cluster.py
@@ -143,9 +143,25 @@ if __name__ == '__main__':
     df['theta'] = np.arccos(df['z'].values/df['r'].values)*1000.
     df['eta'] = -np.log(np.tan(df['theta'].values/1000./2.))
 
+    # Read all mc particles
+    ########################
+    dfallmcp = get_all_mcp(args.file, args.iev, 'mcparticles2')
+    # Select decaying particles
+    dfdecaymcp = dfallmcp[dfallmcp['g4Parent'] == 1.0]
+    pdgbase = ROOT.TDatabasePDG()
+    for iptl in [0, len(dfdecaymcp) - 1]:
+        infoptl = pdgbase.GetParticle(int(dfdecaymcp['pid'].iloc[iptl]))
+        print("{} Decaying particle = {}, pdgcode = {}, charge = {}, mass = {}"\
+            .format(iptl, infoptl.GetName(), infoptl.PdgCode(), infoptl.Charge(), infoptl.Mass()))
+    # Calculate geometric variables of decaying particles
+    dfdecaymcp['r'] = np.sqrt(dfdecaymcp['vex'].values**2 + dfdecaymcp['vey'].values**2 + dfdecaymcp['vez'].values**2)
+    dfdecaymcp['phi'] = np.arctan2(dfdecaymcp['vey'].values, dfdecaymcp['vex'].values)*1000.
+    dfdecaymcp['theta'] = np.arccos(dfdecaymcp['vez'].values/dfdecaymcp['r'].values)*1000.
+    dfdecaymcp['eta'] = -np.log(np.tan(dfdecaymcp['theta'].values/1000./2.))
+
     # truth
     dfmcp = get_mcp_simple(args.file, args.iev, 'mcparticles2').iloc[0]
-    pdgbase = ROOT.TDatabasePDG()
+    #pdgbase = ROOT.TDatabasePDG()
     inpart = pdgbase.GetParticle(int(dfmcp['pid']))
     print("Incoming particle = {}, pdgcode = {}, charge = {}, mass = {}"\
           .format(inpart.GetName(), inpart.PdgCode(), inpart.Charge(), inpart.Mass()))
@@ -216,6 +232,8 @@ if __name__ == '__main__':
     ax, sm = draw_heatmap(axs[0], df['eta'].values, df['phi'].values, weights=df['edep'].values,
                           bins=(np.arange(*eta_rg, step=args.topo_size/1000.), np.arange(*phi_rg, step=args.topo_size)),
                           cmap=cmap, cmin=0., pc_kw=dict(alpha=0.8, edgecolor='k'))
+    # draw true decaying particle position 
+    ax.scatter(dfdecaymcp['eta'].values, dfdecaymcp['phi'].values, marker='x', color='red', s=22**2, linewidth=5.0)
 
     ax.set_ylabel(r'$\phi$ (mrad)', fontsize=32)
     ax.set_xlabel(r'$\eta$', fontsize=32)
diff --git a/benchmarks/imaging_ecal/scripts/utils.py b/benchmarks/imaging_ecal/scripts/utils.py
index da9954ac3e2dc1b0b36009c16fe97c25195394de..740e3ac19f0343a1fc87589d365bc07ac9f24bd5 100644
--- a/benchmarks/imaging_ecal/scripts/utils.py
+++ b/benchmarks/imaging_ecal/scripts/utils.py
@@ -3,6 +3,10 @@
 
     Author: Chao Peng (ANL)
     Date: 04/30/2021
+
+    Added all mc particle info to obtain decaying particles
+    Author: Jihee Kim (ANL)
+    Date: 08/06/2021
 '''
 
 import os
@@ -79,6 +83,31 @@ def get_mcp_simple(path, evnums=None, branch='mcparticles2'):
         idb += 1
     return pd.DataFrame(data=dbuf[:idb], columns=['event', 'px', 'py', 'pz', 'pid', 'status'])
 
+#######################################
+# read all mc particles from root file
+#######################################
+def get_all_mcp(path, evnums=None, branch='mcparticles2'):
+    f = ROOT.TFile(path)
+    events = f.events
+    if evnums is None:
+        evnums = np.arange(events.GetEntries())
+    elif isinstance(evnums, int):
+        evnums = [evnums]
+
+    dbuf = np.zeros(shape=(2000*len(evnums), 10))
+    idb = 0
+    for iev in evnums:
+        if iev >= events.GetEntries():
+            print('Error: event {:d} is out of range (0 - {:d})'.format(iev, events.GetEntries() - 1))
+            continue
+
+        events.GetEntry(iev)
+        # extract mc particle data
+        for ptl in getattr(events, branch):
+            dbuf[idb] = (iev, ptl.psx, ptl.psy, ptl.psz, ptl.pdgID, ptl.status, ptl.g4Parent, ptl.vex, ptl.vey, ptl.vez)
+            idb += 1
+    
+    return pd.DataFrame(data=dbuf[:idb], columns=['event', 'px', 'py', 'pz', 'pid', 'status', 'g4Parent', 'vex', 'vey', 'vez'])
 
 # read hits data from root file
 def get_hits_data(path, evnums=None, branch='RecoEcalBarrelHits'):