Difference between revisions of "Mattione GlueX Kinematic Fitting"

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(Currently Supported)
(Manual Kinematic Fit Example)
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== Manual Kinematic Fit Example ==
 
== Manual Kinematic Fit Example ==
 
* This example shows how to manually perform a kinematic fit (and cut on it's confidence level) inside of a DAnalysisAction.  
 
* This example shows how to manually perform a kinematic fit (and cut on it's confidence level) inside of a DAnalysisAction.  
** This assumes that the DReaction is setup as &gamma;, p &rarr; K<sup>+</sup>, &Lambda; and &Lambda; &rarr; p, &pi;<sup>-</sup>
+
** This assumes that the DReaction is setup as &gamma;, p &rarr; K<sup>+</sup>, &Lambda;; &Lambda; &rarr; p, &pi;<sup>-</sup>
 
* DKinFitAction_Sample.h:
 
* DKinFitAction_Sample.h:
 
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Revision as of 20:48, 13 October 2012

Quick Start

  • It's fully integrated into the analysis suite, so to kinematically fit a DReaction you only have to specify the desired kinematic fit type in the DReaction.

Currently Supported

  • Multiple, simultaneous 4-Momentum Constraints and Vertex Constraints, except for the cases outlined in the "Currently Unsupported" section.

Currently Unsupported

  • P4 or vertex constraints with "few" detected particles.
    • e.g. γ, p → K+, Λ; Λ → p, π- works fine, but it doesn't work if any one of the charged particles is missing.
  • Using decaying particles to constrain vertices together
  • Performing any spacetime fits.

Manual Kinematic Fit Example

  • This example shows how to manually perform a kinematic fit (and cut on it's confidence level) inside of a DAnalysisAction.
    • This assumes that the DReaction is setup as γ, p → K+, Λ; Λ → p, π-
  • DKinFitAction_Sample.h:
#ifndef _DKinFitAction_Sample_
#define _DKinFitAction_Sample_
 
#include "JANA/JEventLoop.h"
#include "DANA/DApplication.h"
 
#include "ANALYSIS/DAnalysisAction.h"
#include "ANALYSIS/DKinFitter_GlueX.h"
#include "ANALYSIS/DKinFitParticle.h"
#include "ANALYSIS/DParticleCombo.h"
 
using namespace std;
using namespace jana;
 
class DKinFitAction_Sample : public DAnalysisAction
{
  public:
    DKinFitAction_Sample(const DReaction* locReaction, string locActionUniqueString = "") : 
    DAnalysisAction(locReaction, "KinFit_Sample", false, locActionUniqueString){}
 
  private:
    bool Perform_Action(JEventLoop* locEventLoop, const DParticleCombo* locParticleCombo, const deque<pair<const DParticleCombo*, bool> >& locPreviousParticleCombos);
    inline void Initialize(JEventLoop* locEventLoop){} //create any histograms here
 
    //define any histograms here
};
 
#endif // _DKinFitAction_Sample_
  • DKinFitAction_Sample.cc:
#include "DKinFitAction_Sample.h"
bool DKinFitAction_Sample::Perform_Action(JEventLoop* locEventLoop, const DParticleCombo* locParticleCombo, const deque<pair<const DParticleCombo*, bool> >& locPreviousParticleCombos)
{
  //THIS ASSUMES DParticleCombo (read: DReaction) is setup as:
    //g, p -> K+, Lambda
    //Lambda -> p, pi-
 
  DKinFitter_GlueX locKinFitter;
  DApplication* locApplication = dynamic_cast<DApplication*>(locEventLoop->GetJApplication());
  locKinFitter.Set_BField(locApplication->GetBfield()); //need call only once
  locKinFitter.Reset_NewEvent(); //need to call prior to use in each event (cleans up memory allocated from last event)
 
  //CREATE DKINFITPARTICLE OBJECTS FOR EACH PARTICLE
  const DBeamPhoton* locBeamPhoton = static_cast<const DBeamPhoton*>(locParticleCombo->Get_ParticleComboStep(0)->Get_InitialParticle_Measured());
  const DKinFitParticle* locKinFitParticle_BeamPhoton = locKinFitter.Make_BeamParticle(locBeamPhoton);
 
  const DKinFitParticle* locKinFitParticle_Target = locKinFitter.Make_TargetParticle(Proton);
  const DKinFitParticle* locKinFitParticle_Lambda = locKinFitter.Make_DecayingParticle(Lambda);
 
  const DChargedTrackHypothesis* locChargedTrackHypothesis_KPlus = static_cast<const DChargedTrackHypothesis*>(locParticleCombo->Get_ParticleComboStep(0)->Get_FinalParticle_Measured(0));
  const DKinFitParticle* locKinFitParticle_KPlus = locKinFitter.Make_DetectedParticle(locChargedTrackHypothesis_KPlus);
 
  const DChargedTrackHypothesis* locChargedTrackHypothesis_Proton = static_cast<const DChargedTrackHypothesis*>(locParticleCombo->Get_ParticleComboStep(1)->Get_FinalParticle_Measured(0));
  const DKinFitParticle* locKinFitParticle_Proton = locKinFitter.Make_DetectedParticle(locChargedTrackHypothesis_Proton);
 
  const DChargedTrackHypothesis* locChargedTrackHypothesis_PiMinus = static_cast<const DChargedTrackHypothesis*>(locParticleCombo->Get_ParticleComboStep(1)->Get_FinalParticle_Measured(1));
  const DKinFitParticle* locKinFitParticle_PiMinus = locKinFitter.Make_DetectedParticle(locChargedTrackHypothesis_PiMinus);
 
  // SETUP THE CONSTRAINTS
  locKinFitter.Reset_NewFit(); //disregards the constraints from the previous kinematic fit
  deque<const DKinFitParticle*> locInitialKinFitParticles, locFinalKinFitParticles;
 
  // first p4 constraint:
  locInitialKinFitParticles.push_back(locKinFitParticle_BeamPhoton);
  locInitialKinFitParticles.push_back(locKinFitParticle_Target);
  locFinalKinFitParticles.push_back(locKinFitParticle_KPlus);
  locFinalKinFitParticles.push_back(locKinFitParticle_Lambda);
  locKinFitter.Add_P4Constraint(locInitialKinFitParticles, locFinalKinFitParticles);
 
  // second p4 constraint:
  locInitialKinFitParticles.clear();
  locFinalKinFitParticles.clear();
  locInitialKinFitParticles.push_back(locKinFitParticle_Lambda);
  locFinalKinFitParticles.push_back(locKinFitParticle_PiMinus);
  locFinalKinFitParticles.push_back(locKinFitParticle_Proton);
  locKinFitter.Add_P4Constraint(locInitialKinFitParticles, locFinalKinFitParticles);
 
  // vertex constraint
  TVector3 locVertexGuess(locKinFitParticle_Proton->Get_Position()); //try to get a better vertex guess than this!
  locInitialKinFitParticles.clear();
  locFinalKinFitParticles.clear();
  locInitialKinFitParticles.push_back(locKinFitParticle_Lambda); //here the lambda isn't constraining the vertex (since it's only in one vertex fit); instead it's vertex will be defined by the fit result
  locFinalKinFitParticles.push_back(locKinFitParticle_PiMinus);
  locFinalKinFitParticles.push_back(locKinFitParticle_Proton);
  locKinFitter.Add_VertexConstraint(locInitialKinFitParticles, locFinalKinFitParticles, locVertexGuess);
 
  // PERFORM THE KINEMATIC FIT
  locKinFitter.Fit_Reaction();
 
  // GET THE FIT RESULTS
  double locConfidenceLevel = locKinFitter.Get_ConfidenceLevel();
  double locChiSq = locKinFitter.Get_ChiSq();
  unsigned int locNDF = locKinFitter.Get_NDF();
  const TMatrixDSym* locMeasuredParametersKinFitCovarianceMatrix = locKinFitter.Get_VEta();
  const TMatrixDSym* locUnknownParametersCovarianceMatrix = locKinFitter.Get_VXi();
 
  DKinFitParticle* locKinFitParticle_Proton_Output = locKinFitter.Get_OutputKinFitParticle(locKinFitParticle_Proton);
  DKinFitParticle* locKinFitParticle_PiMinus_Output = locKinFitter.Get_OutputKinFitParticle(locKinFitParticle_PiMinus);
  DKinFitParticle* locKinFitParticle_KPlus_Output = locKinFitter.Get_OutputKinFitParticle(locKinFitParticle_KPlus);
  DKinFitParticle* locKinFitParticle_Lambda_Output = locKinFitter.Get_OutputKinFitParticle(locKinFitParticle_Lambda);
  DKinFitParticle* locKinFitParticle_BeamPhoton_Output = locKinFitter.Get_OutputKinFitParticle(locKinFitParticle_BeamPhoton);
  TVector3 locKinFitVertex = locKinFitParticle_PiMinus_Output->Get_CommonVertex(); //could also be grabbed from the proton or the lambda
 
  map<const DKinematicData*, map<DKinFitPullType, double> > locPulls; //map from input particle data to pull map //pull map: map from pull type to value (DKinFitPullType defined in DKinFitParticle.h)
  locKinFitter.Get_Pulls(locPulls);
  double locProtonPxPull = (locPulls[locChargedTrackHypothesis_Proton])[d_PxPull];
 
  //fill histograms, etc. here
  return (locConfidenceLevel >= 0.01); //cut if < 1% confidence level
}