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TFitParticleSpher.cc

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// Classname: TFitParticleSpher
// Author: Jan E. Sundermann, Verena Klose (TU Dresden)      


//________________________________________________________________
// 
// TFitParticleSpher::
// --------------------
//
// Particle with spherical  parametrization of the momentum 4vector and
// free mass (4 free parameters). The parametrization is chosen as
// follows:
//
// p = (r, theta, phi)
// E(fit) =  Sqrt( |p|^2 + d^2*m^2 )
//

using namespace std;

#include <iostream>
#include "FWCore/MessageLogger/interface/MessageLogger.h"
#include "PhysicsTools/KinFitter/interface/TFitParticleSpher.h"
#include "TMath.h"

ClassImp(TFitParticleSpher)

//----------------
// Constructor --
//----------------
TFitParticleSpher::TFitParticleSpher()
  :TAbsFitParticle()  
{
  init(0, 0);
}

TFitParticleSpher::TFitParticleSpher( const TFitParticleSpher& fitParticle )
  :TAbsFitParticle( fitParticle.GetName(), fitParticle.GetTitle() )
{

  _nPar = fitParticle._nPar;
  _u1 = fitParticle._u1;
  _u2 = fitParticle._u2;
  _u3 = fitParticle._u3;
  _covMatrix.ResizeTo(  fitParticle._covMatrix );
  _covMatrix = fitParticle._covMatrix;
  _iniparameters.ResizeTo( fitParticle._iniparameters );
  _iniparameters = fitParticle._iniparameters;
  _parameters.ResizeTo( fitParticle._parameters );
  _parameters = fitParticle._parameters;
  _pini = fitParticle._pini;
  _pcurr = fitParticle._pcurr;

}

TFitParticleSpher::TFitParticleSpher(TLorentzVector* pini, const TMatrixD* theCovMatrix)
  :TAbsFitParticle()  
{
  init(pini, theCovMatrix);
}

TFitParticleSpher::TFitParticleSpher(const TString &name, const TString &title, 
                           TLorentzVector* pini, const TMatrixD* theCovMatrix)
  :TAbsFitParticle(name, title)  
{
  init(pini, theCovMatrix);
}

TAbsFitParticle* TFitParticleSpher::clone( TString newname ) const {
  // Returns a copy of itself
  
  TAbsFitParticle* myclone = new TFitParticleSpher( *this );
  if ( newname.Length() > 0 ) myclone->SetName(newname);
  return myclone;

}

//--------------
// Destructor --
//--------------
TFitParticleSpher::~TFitParticleSpher() {

}

//--------------
// Operations --
//--------------
void TFitParticleSpher::init(TLorentzVector* pini, const TMatrixD* theCovMatrix ) {

  _nPar = 4;
  setIni4Vec(pini);
  setCovMatrix(theCovMatrix);

}

TLorentzVector* TFitParticleSpher::calc4Vec( const TMatrixD* params ) {
  // Calculates a 4vector corresponding to the given
  // parameter values

  if (params == 0) {
    return 0;
  }

  if ( params->GetNcols() != 1 || params->GetNrows() !=_nPar ) {
    edm::LogError ("WrongMatrixSize")
      << GetName() << "::calc4Vec - Parameter matrix has wrong size.";
    return 0;
  }

  Double_t r = (*params)(0,0);
  Double_t theta = (*params)(1,0);
  Double_t phi = (*params)(2,0);
  Double_t d = (*params)(3,0);

  Double_t X = r*TMath::Cos(phi)*TMath::Sin(theta);
  Double_t Y = r*TMath::Sin(phi)*TMath::Sin(theta);
  Double_t Z = r*TMath::Cos(theta);
  Double_t E = TMath::Sqrt( X*X + Y*Y + Z*Z + d*d*_pini.M2() );
                
  TLorentzVector* vec = new TLorentzVector( X, Y, Z, E );
  return vec;

}

void TFitParticleSpher::setIni4Vec(const TLorentzVector* pini) {
  // Set the initial 4vector. Will also set the 
  // inital parameter values 

  if (pini == 0) {

    _u1.SetXYZ(0., 0., 0.);
    _u3.SetXYZ(0., 0., 0.);
    _u2.SetXYZ(0., 0., 0.);
    _pini.SetXYZT(0., 0., 0., 0.);
    _pcurr = _pini;

    _iniparameters.ResizeTo(_nPar,1);
    _iniparameters(0,0) = 0.;
    _iniparameters(1,0) = 0.;
    _iniparameters(2,0) = 0.;
    _iniparameters(3,0) = 1.;
    
    _parameters.ResizeTo(_nPar,1);
    _parameters(0,0) = 0.;
    _parameters(1,0) = 0.;
    _parameters(2,0) = 0.;   
    _parameters(3,0) = 1.;   
    
  } else {
    
    Double_t r = pini->P();
    Double_t theta = pini->Theta();
    Double_t phi = pini->Phi();
    
    _pini = (*pini);
    _pcurr = _pini;
    
    _iniparameters.ResizeTo(_nPar,1);
    _iniparameters(0,0) = r;
    _iniparameters(1,0) = theta;
    _iniparameters(2,0) = phi;
    _iniparameters(3,0) = 1.;
    
    _parameters.ResizeTo(_nPar,1);
    _parameters = _iniparameters;

    _u1.SetXYZ( TMath::Cos(phi)*TMath::Sin(theta), TMath::Sin(phi)*TMath::Sin(theta), TMath::Cos(theta) );
    _u2.SetXYZ( TMath::Cos(phi)*TMath::Cos(theta), TMath::Sin(phi)*TMath::Cos(theta), -1.*TMath::Sin(theta) );
    _u3.SetXYZ( -1.*TMath::Sin(phi), TMath::Cos(phi), 0. );

  }

}

TMatrixD* TFitParticleSpher::getDerivative() {
  // returns derivative dP/dy with P=(p,E) and y=(r, theta, phi, d) 
  // the free parameters of the fit. The columns of the matrix contain 
  // (dP/dr, dP/dtheta, ...).

  TMatrixD* DerivativeMatrix = new TMatrixD(4,4);
  (*DerivativeMatrix) *= 0.;

  Double_t r = _parameters(0,0);
  Double_t theta = _parameters(1,0);
  Double_t phi = _parameters(2,0);
  Double_t d = _parameters(3,0);

  //1st column: dP/dr
  (*DerivativeMatrix)(0,0) = TMath::Cos(phi)*TMath::Sin(theta);
  (*DerivativeMatrix)(1,0) = TMath::Sin(phi)*TMath::Sin(theta);
  (*DerivativeMatrix)(2,0) = TMath::Cos(theta);
  (*DerivativeMatrix)(3,0) = 0.;

  //2nd column: dP/dtheta
  (*DerivativeMatrix)(0,1) = r*TMath::Cos(phi)*TMath::Cos(theta);
  (*DerivativeMatrix)(1,1) = r*TMath::Sin(phi)*TMath::Cos(theta);
  (*DerivativeMatrix)(2,1) = -1.*r*TMath::Sin(theta);
  (*DerivativeMatrix)(3,1) = 0.;

   //3rd column: dP/dphi
  (*DerivativeMatrix)(0,2) = -1.*r*TMath::Sin(phi)*TMath::Sin(theta);
  (*DerivativeMatrix)(1,2) = r*TMath::Cos(phi)*TMath::Sin(theta);;
  (*DerivativeMatrix)(2,2) = 0.;
  (*DerivativeMatrix)(3,2) = 0.;

   //4th column: dP/dm
  (*DerivativeMatrix)(0,3) = 0.;
  (*DerivativeMatrix)(1,3) = 0.;
  (*DerivativeMatrix)(2,3) = 0.;
  (*DerivativeMatrix)(3,3) = _pini.M()*_pini.M()*d/_pcurr.E();

  return DerivativeMatrix;

}

TMatrixD* TFitParticleSpher::transform(const TLorentzVector& vec) {
  // Returns the parameters corresponding to the given 
  // 4vector

  // retrieve parameters
  TMatrixD* tparams = new TMatrixD( _nPar, 1 );
  (*tparams)(0,0) = vec.P();
  (*tparams)(1,0) = vec.Theta();
  (*tparams)(2,0) = vec.Phi();
  (*tparams)(3,0) = vec.M()/_pini.M();

  return tparams;

}

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