PndVtxPoca pocafinder;
for (int j=0; j<lambda0.GetLength(); ++j)
{
  PndKinVtxFitter vertexfitterLambda0 (lambda0[j]);
  vertexfitterLambda0.Fit();
  RhoCandidate * lambda0Fit = lambda0[j]->GetFit();
  for (int j=0; j<antiLambda0.GetLength(); ++j)
  {
    PndKinVtxFitter vertexfitterAntiLambda0 (antiLambda0[j]);
    vertexfitterAntiLambda0.Fit();
    RhoCandidate * antiLambda0Fit = antiLambda0[j]->GetFit();
    
    TVector3 pbarpvertex;
    crossCheck.Combine(lambda0Fit, antiLambda0Fit);
    crossCheck.SetType(88888);

    double doca = pocafinderGetPocaVtx(pbarpvertex,crossCheck);
    // now you have a vertex written to pbarpvertex and a measure of the distances between the trajectories (i.e. a quality criterium)
  }
}

bool check = theAnalysis->PropagateToPoint(crossCheck, pbarpvertex);