message: V0 uncertainties combined in pre-processing step before propagation
diff: @@ -1622,8 +1622,12 @@ void AliAnalysisTaskStrEffStudy::UserExec(Option_t *)
  AliExternalTrackParam btimp(*esdTrackBach), *pbtimp=&btimp;
  //Uncertainties: bachelor track as well as V0
  - Double_t dy2=pbtimp->GetSigmaY2() + esdTrackPos->GetSigmaY2() + esdTrackNeg->GetSigmaY2();
  - Double_t dz2=pbtimp->GetSigmaZ2() + esdTrackPos->GetSigmaZ2() + esdTrackNeg->GetSigmaZ2();
  + //Harmonic mean-like: errors as weights to combine the errors (approx)
  + Double_t dy2V0 = TMath::Power(1/(esdTrackPos->GetSigmaY2()+1e-8)+1/(esdTrackNeg->GetSigmaY2()+1e-8)+1e-8,-1);
  + Double_t dz2V0 = TMath::Power(1/(esdTrackPos->GetSigmaZ2()+1e-8)+1/(esdTrackNeg->GetSigmaZ2()+1e-8)+1e-8,-1);
  +
  + Double_t dy2=pbtimp->GetSigmaY2() + dy2V0;
  + Double_t dz2=pbtimp->GetSigmaZ2() + dz2V0;
  Double_t dx2=dy2;
  //For testing purposes: try geometric criterion only, disregard uncertainties
  