Merge branch 'MEChi2Check' into 'master'

Reject poor muon track extrapolations

See merge request atlas/athena!34915

Reconstruction/MuonIdentification/MuonCombinedBaseTools/src/MuonCandidateTool.cxx

@@ -82,6 +82,22 @@ namespace MuonCombined {
       } else {
          standaloneTrack = m_trackExtrapolationTool->extrapolate(msTrack);
       }
+      if(standaloneTrack){
+	//Reject the track if its fit quality is much (much much) worse than that of the non-extrapolated track
+	if(standaloneTrack->fitQuality()->doubleNumberDoF()==0){
+	  delete standaloneTrack;
+	  standaloneTrack=0;
+	  ATH_MSG_DEBUG("extrapolated track has no DOF, don't use it");
+	}
+	double mschi2=2.5; //a default we should hopefully never have to use (taken from CombinedMuonTrackBuilder)
+	if(msTrack.fitQuality()->doubleNumberDoF()>0) mschi2=msTrack.fitQuality()->chiSquared()/msTrack.fitQuality()->doubleNumberDoF();
+	//choice of 1000 is slightly arbitrary, the point is that the fit should be really be terrible
+	if(standaloneTrack->fitQuality()->chiSquared()/standaloneTrack->fitQuality()->doubleNumberDoF()>1000*mschi2){
+	  delete standaloneTrack;
+	  standaloneTrack=0;
+	  ATH_MSG_DEBUG("extrapolated track has a degraded fit, don't use it");
+        }
+      }
       if (standaloneTrack) {
 	standaloneTrack->info().setParticleHypothesis(Trk::muon);
 	standaloneTrack->info().setPatternRecognitionInfo(Trk::TrackInfo::MuidStandAlone);

Tools/PROCTools/data/master_q431_AOD_digest.ref

@@ -14,7 +14,7 @@
       330470  1183746343         492         465          14           0
       330470  1183746710           6           0           0           0
       330470  1183751782         239         235           5           0
-      330470  1183752624         347         342           8           3
+      330470  1183752624         347         342           8           2
       330470  1183753006         357         377          11           3
       330470  1183754806         470         406          14           0
       330470  1183769295         342         317           8           1