PWGEM: Update pythia config for Dalitz Decay MC (#2348)

Co-authored-by: Laura Gansbartl <lgansbartl@pcikf5.ikf.uni-frankfurt.de>

Author: lgansbartl

MC/config/PWGEM/pythia8/generator/configPythia_ForcedDalitz.cfg

@@ -12,10 +12,9 @@ ParticleDecays:limitTau0 on
 ParticleDecays:tau0Max  10     
 
 
-#decay eta -> e+ e- gamma BR = 100%
-221:onMode = off
-221:onIfMatch = 22 11 -11
-#221:addChannel = 1 1 0 22 11 -11
+#decay eta -> e+ e- gamma, BR = 100%
+221:oneChannel = 1 1 0 22 11 -11
 
 #decay pi0 -> e+ e- gamma BR = 10%
-111:addChannel = 1 0.10 0 22 11 -11"
+111:oneChannel = 1 0.9 0 22 22
+111:addChannel = 1 0.1 0 22 11 -11