Trk::MassConstraint Class Reference

Concrete implementation of Trk::IKinematicConstraint to formulate a mass constraint in kinematic vertex fits. More...

#include <MassConstraint.h>

Inheritance diagram for Trk::MassConstraint:

Collaboration diagram for Trk::MassConstraint:

Public Member Functions
	MassConstraint ()=default
	empty constructor
	MassConstraint (double mass)
	standard constructor
virtual	~MassConstraint ()=default
virtual Amg::VectorX	vectorOfValues (std::vector< Amg::VectorX > &cart_coordList, std::vector< int > &charges, Amg::Vector3D refPoint, double b_fieldTesla) const override final
	method returning the vector of parameters values.
virtual Amg::MatrixX	matrixOfDerivatives (std::vector< Amg::VectorX > &cart_coordList, std::vector< int > &charges, Amg::Vector3D refPoint, double b_fieldTesla) const override final
	method returning the matrix of derivatives.
virtual int	numberOfEquations () const override final
	tells the number of equations needed for this type of constraint, that is 1
double	mass ()
	tells the mass value used for the constraint

Private Attributes
double	m_mass = 0.
	value of mass to be constrained in MeV

Static Private Attributes
static constexpr int	s_eqno = 1
	number of constraint-equations used by this type of constraint

Detailed Description

Concrete implementation of Trk::IKinematicConstraint to formulate a mass constraint in kinematic vertex fits.

The constraint is constructed with a mass value (in MeV), to which the invariant mass of the particles emerging from a vertex will be constrained. It calculates the values and derivatives for a list of particles, given by their parameters and charges.

Author

Maaike Limper

Definition at line 26 of file MassConstraint.h.

Constructor & Destructor Documentation

MassConstraint() [1/2]

Trk::MassConstraint::MassConstraint ( )

default

empty constructor

MassConstraint() [2/2]

Trk::MassConstraint::MassConstraint

(

double

mass

)

standard constructor

Parameters

[in]

mass

Invariant mass in MeV to which particles shall be constrained

Definition at line 12 of file MassConstraint.cxx.

  : m_mass(mass)
{}

~MassConstraint()

virtual Trk::MassConstraint::~MassConstraint ( )

virtualdefault

Member Function Documentation

mass()

double Trk::MassConstraint::mass ( )

inline

tells the mass value used for the constraint

Definition at line 75 of file MassConstraint.h.

{ return m_mass; }

matrixOfDerivatives()

Amg::MatrixX Trk::MassConstraint::matrixOfDerivatives ( std::vector< Amg::VectorX > & cart_coordList, std::vector< int > & charges, Amg::Vector3D refPoint, double b_fieldTesla ) const

finaloverridevirtual

method returning the matrix of derivatives.

Method defined through the <nop>IKinematicConstraint base class

Parameters

[in]	cart_coordList	vector of particles represented in cartesian frame, that is through the parameters (px, py, pz, E, x, y, z).
[in]	charges	charge information for the vector of particles
[in]	refPoint	reference point for cartesian coordinates
[in]	b_fieldTesla	local solenoidal approximation of field
[out]	matrix	of derivatives to enter the constrained-fit equation

Implements Trk::IKinematicConstraint.

Definition at line 60 of file MassConstraint.cxx.

{
 
  const unsigned int ntrack = cart_coordList.size();
 
  Amg::MatrixX matrixDeriv2(1, ntrack * 7);
 
  const double bend_factor = -0.299792458 * b_fieldTesla;
 
  for (unsigned int i = 0; i < ntrack; i++) {
    const double E = cart_coordList[i][3];
    const double px = cart_coordList[i][0];
    const double py = cart_coordList[i][1];
    const double pz = cart_coordList[i][2];
 
    const double deltaX = refPoint[0] - cart_coordList[i][4];
    const double deltaY = refPoint[1] - cart_coordList[i][5];
 
    const double a = charges[i] * bend_factor;
 
    for (unsigned int jtrack = 0; jtrack < ntrack; jtrack++) {
      const unsigned int joff = jtrack * 7;
      matrixDeriv2(0, joff + 0) =
        matrixDeriv2(0, joff + 0) - 2 * (px - a * deltaY);
      matrixDeriv2(0, joff + 1) =
        matrixDeriv2(0, joff + 1) - 2 * (py + a * deltaX);
      matrixDeriv2(0, joff + 2) = matrixDeriv2(0, joff + 2) - 2 * pz;
      matrixDeriv2(0, joff + 3) = matrixDeriv2(0, joff + 3) + 2 * E;
 
      // shouldn't this go to 0 when deltaX = 0 ?! no! when vertex moves px,py
      // moves and vice-versa so derivative of vertex should depend on px,py
      matrixDeriv2(0, joff + 4) =
        matrixDeriv2(0, joff + 4) + 2 * a * (py + a * deltaX);
      matrixDeriv2(0, joff + 5) =
        matrixDeriv2(0, joff + 5) - 2 * a * (px - a * deltaY);
      //(*p_matrixDeriv)[0][joff+6] = (*p_matrixDeriv)[0][joff+6] + 0.; // no
      //dependence on z!
    }
  }
 
  return matrixDeriv2;
}

numberOfEquations()

virtual int Trk::MassConstraint::numberOfEquations ( ) const

inlinefinaloverridevirtual

tells the number of equations needed for this type of constraint, that is 1

Implements Trk::IKinematicConstraint.

Definition at line 72 of file MassConstraint.h.

{ return s_eqno; }

vectorOfValues()

Amg::VectorX Trk::MassConstraint::vectorOfValues ( std::vector< Amg::VectorX > & cart_coordList, std::vector< int > & charges, Amg::Vector3D refPoint, double b_fieldTesla ) const

finaloverridevirtual

method returning the vector of parameters values.

Method defined through the <nop>IKinematicConstraint base class

Parameters

[in]	cart_coordList	vector of particles represented in cartesian frame, that is through the parameters (px, py, pz, E, x, y, z).
[in]	charges	charge information for the vector of particles
[in]	refPoint	reference point for cartesian coordinates
[in]	b_fieldTesla	local solenoidal approximation of field
[out]	vector	of values to enter the constrained-fit equation

Implements Trk::IKinematicConstraint.

Definition at line 17 of file MassConstraint.cxx.

{
 
  unsigned int ntrack = cart_coordList.size();
 
  Amg::VectorX vectorOfValues2(1, 0);
 
  const double bend_factor = -0.299792458 * b_fieldTesla;
 
  double Etot = 0.;
  double Px = 0.;
  double Py = 0.;
  double Pz = 0.;
 
  for (unsigned int i = 0; i < ntrack; i++) {
    const double E = cart_coordList[i][3];
    const double px = cart_coordList[i][0];
    const double py = cart_coordList[i][1];
    const double pz = cart_coordList[i][2];
 
    const double deltaX = refPoint[0] - cart_coordList[i][4];
    const double deltaY = refPoint[1] - cart_coordList[i][5];
 
    const double a = charges[i] * bend_factor;
 
    // sum of values of cartesian coordinates at given reference-point
    Etot += E;
    Px += (px - a * deltaY);
    Py += (py + a * deltaX);
    Pz += pz;
  }
 
  vectorOfValues2[0] =
    Etot * Etot - Px * Px - Py * Py - Pz * Pz -
    m_mass * m_mass; // fill vector using sums made in track-loop
 
  return vectorOfValues2;
}

Member Data Documentation

m_mass

double Trk::MassConstraint::m_mass = 0.

private

value of mass to be constrained in MeV

Definition at line 79 of file MassConstraint.h.

s_eqno

int Trk::MassConstraint::s_eqno = 1

staticconstexprprivate

number of constraint-equations used by this type of constraint

Definition at line 81 of file MassConstraint.h.

---

The documentation for this class was generated from the following files:

• MassConstraint.h
• MassConstraint.cxx