diff -u -r1.1 -r1.2
--- RemoveUnusedMcParticles.java	4 Jul 2012 13:54:36 -0000	1.1
+++ RemoveUnusedMcParticles.java	20 Aug 2012 09:40:44 -0000	1.2
@@ -47,14 +47,18 @@

 		this.keepGeneratorParticles = keepGeneratorParticles;
 	}
 

+	public void setIgnoreCollection(String collectionName) {
+		ignoredCollections.add(collectionName);
+	}
+	

 	/**
 	 * Mc particles that contributed to the given list of collections will not
 	 * be kept.
 	 * 
 	 * @param ignoredCollections
 	 */

-	public void setIgnoredCollections(String[] ignoredCollections) {
-		this.ignoredCollections = Arrays.asList(ignoredCollections);

+	public void setIgnoreCollections(String[] collectionNames) {
+		ignoredCollections.addAll(Arrays.asList(collectionNames));

 	}
 
 	@Override

@@ -107,10 +111,8 @@

 			}
 		}
 		

-		// replace the list of mc particles in the event
-		int flags = event.getMetaData(mcParticles).getFlags();
-		event.remove(mcParticleCollection);
-		event.put(mcParticleCollection, mcParticlesToKeep, MCParticle.class, flags);

+		// remove all mc particles except for those to keep
+		mcParticles.retainAll(mcParticlesToKeep);

 	}
 
 	/**