Try to generate a simple “analysis skeleton” using:
mc_c.MakeClass(“Trial”);
and then have a look into the generated “Trial.C” file, into the “Trial::Loop” skeleton.
See also: How are multiple TTree->Draw()s done?
BTW. You should NOT have “;1” in the name of the chain, it should simply be:
TChain mc_c(“KPiPiPiMassMeasTuple/DecayTree”);