TFitParticleCart.cc

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

//________________________________________________________________
//
// TFitParticleCart::
// --------------------
//
// Particle with cartesian 4vector parametrization and free mass
// [four free parameters (px, py, pz, d) with initial values
//  (px, py, pz, 1)]
//
// p = px*u1 + py*u2 + pz*u3
// E = Sqrt( |p|^2 + d^2*m^2 )
//

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

//----------------
// Constructor --
//----------------
TFitParticleCart::TFitParticleCart() : TAbsFitParticle() { init(nullptr, nullptr); }

TFitParticleCart::TFitParticleCart(const TFitParticleCart& 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;
}

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

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

TAbsFitParticle* TFitParticleCart::clone(const TString& newname) const {
  // Returns a copy of itself

  TAbsFitParticle* myclone = new TFitParticleCart(*this);
  if (newname.Length() > 0)
    myclone->SetName(newname);
  return myclone;
}

//--------------
// Destructor --
//--------------
TFitParticleCart::~TFitParticleCart() {}

//--------------
// Operations --
//--------------
void TFitParticleCart::init(TLorentzVector* pini, const TMatrixD* theCovMatrix) {
  _nPar = 4;
  setIni4Vec(pini);
  setCovMatrix(theCovMatrix);
}

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

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

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

  Double_t X = (*params)(0, 0);
  Double_t Y = (*params)(1, 0);
  Double_t Z = (*params)(2, 0);
  Double_t E = TMath::Sqrt(X * X + Y * Y + Z * Z + (*params)(3, 0) * (*params)(3, 0) * _pini.M2());

  TLorentzVector* vec = new TLorentzVector(X, Y, Z, E);
  return vec;
}

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

  if (pini == nullptr) {
    _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) = 0.;

    _parameters.ResizeTo(_nPar, 1);
    _parameters(0, 0) = 0.;
    _parameters(1, 0) = 0.;
    _parameters(2, 0) = 0.;
    _parameters(3, 0) = 0.;

  } else {
    _pini = (*pini);
    _pcurr = _pini;

    _u1.SetXYZ(1., 0., 0.);
    _u2.SetXYZ(0., 1., 0.);
    _u3.SetXYZ(0., 0., 1.);

    _iniparameters.ResizeTo(_nPar, 1);
    _iniparameters(0, 0) = _pini.X();
    _iniparameters(1, 0) = _pini.Y();
    _iniparameters(2, 0) = _pini.Z();
    _iniparameters(3, 0) = 1.;
    _parameters.ResizeTo(_nPar, 1);
    _parameters = _iniparameters;
  }
}

TMatrixD* TFitParticleCart::getDerivative() {
  // returns derivative dP/dy with P=(p,E) and y=(px, py, pz, d)
  // the free parameters of the fit. The columns of the matrix contain
  // (dP/dpx, dP/dpy, ...).

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

  //1st column: dP/dx
  (*DerivativeMatrix)(0, 0) = 1.;
  (*DerivativeMatrix)(1, 0) = 0.;
  (*DerivativeMatrix)(2, 0) = 0.;
  (*DerivativeMatrix)(3, 0) = 0.;

  //2nd column: dP/dy
  (*DerivativeMatrix)(0, 1) = 0;
  (*DerivativeMatrix)(1, 1) = 1;
  (*DerivativeMatrix)(2, 1) = 0;
  (*DerivativeMatrix)(3, 1) = 0.;

  //3rd column: dP/dz
  (*DerivativeMatrix)(0, 2) = 0.;
  (*DerivativeMatrix)(1, 2) = 0.;
  (*DerivativeMatrix)(2, 2) = 1.;
  (*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() * _parameters(3, 0) / _pcurr.E();

  return DerivativeMatrix;
}

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

  TMatrixD* tparams = new TMatrixD(_nPar, 1);
  (*tparams)(0, 0) = vec.X();
  (*tparams)(1, 0) = vec.Y();
  (*tparams)(2, 0) = vec.Z();
  (*tparams)(3, 0) = vec.M() / _pini.M();

  return tparams;
}