Describe track selection process

[bdrum]

This is the code that response for track selection

 if (trk->IsOn(AliESDtrack::kITSpureSA))
        return false;
    if (!(trk->GetStatus() & AliESDtrack::kTPCrefit))
        return false;
    if (!(trk->GetStatus() & AliESDtrack::kITSrefit))
        return false;
    if (trk->GetTPCNcls() < 50)
        return false;
    if (!((trk->HasPointOnITSLayer(0)) || (trk->HasPointOnITSLayer(1))))
        return false;

    // if(trk->GetTPCchi2()/trk->GetTPCNcls() > 4)continue;

    Float_t dca[2] = { 0.0, 0.0 };
   
    trk->GetImpactParameters(dca[0], dca[1]);
    if (TMath::Abs(dca[1]) > 2)
        return false;

    Double_t cut_DCAxy = (0.0182 + 0.0350 / TMath::Power(trk->Pt(), 1.01));
    if (TMath::Abs(dca[0]) > cut_DCAxy)
        return false;

Describe each component of this code and physics that stay behind this.