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Fxt offset vtx #720

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merged 6 commits into from
Dec 10, 2024
Merged

Fxt offset vtx #720

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5328356
Set up FXT mode in vertex-finding
genevb Oct 22, 2024
afda1d7
More detailed comment
genevb Oct 23, 2024
9f57719
Merge branch 'star-bnl:main' into FXT_OFFSET_VTX
genevb Dec 10, 2024
f7c1802
Exclude documentation files
genevb Dec 10, 2024
c4bfd80
Needed to include a change in z of DCA
genevb Dec 10, 2024
aedef64
minor optimization: square once vs. sqrt N times
genevb Dec 10, 2024
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1 change: 1 addition & 0 deletions StRoot/StBFChain/StBFChain.cxx
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Expand Up @@ -580,6 +580,7 @@ Int_t StBFChain::Instantiate()
if (GetOption("usePct4Vtx" ) ) mk->SetAttr("PCT" , kTRUE);
if (GetOption("useBTOF4Vtx") ) mk->SetAttr("BTOF" , kTRUE);
if (GetOption("useBTOFmatchOnly") ) mk->SetAttr("useBTOFmatchOnly", kTRUE);
if (GetOption("FXT" ) ) mk->SetAttr("FXT" , kTRUE);

// X-tended works only for VFPPV, VFPPVnoCTB, VFPPVev for now but could be re-used
// However, we will change this to a more flexible arbitrarry setting later
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15 changes: 13 additions & 2 deletions StRoot/StGenericVertexMaker/Minuit/StMinuitVertexFinder.cxx
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Expand Up @@ -55,6 +55,7 @@ StMinuitVertexFinder::StMinuitVertexFinder(VertexFit_t fitMode) :
mExternalSeedPresent = kFALSE;
mRequireCTB = kFALSE;
requireCTB = kFALSE;
mFXT = kFALSE;
mUseITTF = kFALSE;
mUseOldBEMCRank = kFALSE;
mLowerSplitVtxRank = kFALSE;
Expand Down Expand Up @@ -407,19 +408,29 @@ int StMinuitVertexFinder::fit(StEvent* event)
Int_t n_bemc_match_tot = 0;
Int_t n_cross_tot = 0;

// In FXT mode, we want to have a bias = -2 cm below the z-axis
// for the approximate physical target location. This could
// potentially be a database table (PrimaryVertexCuts) parameter,
// but the bias is approximate and highly unlikely to change/finetune.
StThreeVectorD beamAxis(0.0, mFXT ? -2.0 : 0.0, 0.0);
double RImpactMax2 = mRImpactMax*mRImpactMax;

for (const StTrackNode* stTrack : event->trackNodes())
{
StGlobalTrack* g = ( StGlobalTrack*) stTrack->track(global);
if (!accept(g)) continue;
StDcaGeometry* gDCA = g->dcaGeometry();
if (! gDCA) continue;
if (TMath::Abs(gDCA->impact()) > mRImpactMax) continue;
StPhysicalHelixD gHelix = gDCA->helix();
StThreeVectorD DCAPosition = gHelix.at(gHelix.pathLength(beamAxis.x(),beamAxis.y())) - beamAxis;
double RImpact2 = DCAPosition.perp2();
if (RImpact2 > RImpactMax2) continue; // calculate square once instead of sqrt N times
mDCAs.push_back(gDCA);
// StPhysicalHelixD helix = gDCA->helix();
// mHelices.push_back(helix);
mHelices.push_back(g->geometry()->helix());
mHelixFlags.push_back(1);
Double_t z_lin = gDCA->z();
Double_t z_lin = DCAPosition.z();
mZImpact.push_back(z_lin);

Bool_t shouldHitCTB = kFALSE;
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2 changes: 2 additions & 0 deletions StRoot/StGenericVertexMaker/Minuit/StMinuitVertexFinder.h
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Expand Up @@ -130,6 +130,7 @@ class StMinuitVertexFinder: public StGenericVertexFinder
void setFlagBase();
void SetFitPointsCut(Int_t fitpoints) {mMinNumberOfFitPointsOnTrack = fitpoints;}
void SetMinimumTracks(Int_t n) {mMinTrack = n;}
void SetFXT(bool fxt=kTRUE) { mFXT = fxt; }

private:

Expand All @@ -151,6 +152,7 @@ class StMinuitVertexFinder: public StGenericVertexFinder
bool mLowerSplitVtxRank;// Use lower rank for split vertices
UInt_t mFlagBase; // ITTF track flag
bool mRequireCTB; // Set maker to use CTB
bool mFXT; // Switch on FXT mode
UInt_t mMinNumberOfFitPointsOnTrack;
Float_t mDcaZMax;
Double_t mRImpactMax; // Max distance between helix and nominal beamline (0,0,z)
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1 change: 1 addition & 0 deletions StRoot/StGenericVertexMaker/StGenericVertexMaker.cxx
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Expand Up @@ -112,6 +112,7 @@ Int_t StGenericVertexMaker::Init()

if (IAttr("VFMinuit") ) ((StMinuitVertexFinder*) theFinder)->useOldBEMCRank();
if (IAttr("VFMinuit3") ) ((StMinuitVertexFinder*) theFinder)->lowerSplitVtxRank();
if (IAttr("FXT") ) ((StMinuitVertexFinder*) theFinder)->SetFXT();
if (minTracks > 0) ((StMinuitVertexFinder*) theFinder)->SetMinimumTracks(minTracks);

} else if ( IAttr("VFppLMV")){
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