const Var kPrimMuonIdx([](const caf::SRSliceProxy *slc) -> double{if((int) slc->reco.ntrk==0) return-5.0;double best_idx=0;double best_len=-5.0;for(unsigned int trkIdx=0;trkIdx< slc->reco.ntrk;trkIdx++){auto &trk=slc->reco.trk[trkIdx];if(trk.chi2pid[2].pid_ndof< 0) return-5.0;bool isMuonLike=trk.chi2pid[2].chi2_pion > trk.chi2pid[2].chi2_muon;if(isMuonLike &&trk.len > best_len){best_len=trk.len;best_idx=trkIdx;}}return best_idx;})